Revert "Revert "Revert "[clang][UBSan] Add implicit conversion check for bitfields""" (#87562)

Reverts llvm/llvm-project#87529

Reverts #87518

https://lab.llvm.org/buildbot/#/builders/37/builds/33262 is still broken

11 files changed, 73 insertions, 493 deletions

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index e4c0e49ed6fc..8fc925350849 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -198,10 +198,6 @@ Non-comprehensive list of changes in this release
 
 New Compiler Flags
 ------------------
-- ``-fsanitize=implicit-bitfield-conversion`` checks implicit truncation and
-  sign change.
-- ``-fsanitize=implicit-integer-conversion`` a group that replaces the previous
-  group ``-fsanitize=implicit-conversion``.
 
 - ``-Wmissing-designated-field-initializers``, grouped under ``-Wmissing-field-initializers``.
   This diagnostic can be disabled to make ``-Wmissing-field-initializers`` behave
@@ -215,9 +211,6 @@ Modified Compiler Flags
 - Added a new diagnostic flag ``-Wreturn-mismatch`` which is grouped under
   ``-Wreturn-type``, and moved some of the diagnostics previously controlled by
   ``-Wreturn-type`` under this new flag. Fixes #GH72116.
-- ``-fsanitize=implicit-conversion`` is now a group for both
-  ``-fsanitize=implicit-integer-conversion`` and
-  ``-fsanitize=implicit-bitfield-conversion``.
 
 - Added ``-Wcast-function-type-mismatch`` under the ``-Wcast-function-type``
   warning group. Moved the diagnostic previously controlled by
diff --git a/clang/docs/UndefinedBehaviorSanitizer.rst b/clang/docs/UndefinedBehaviorSanitizer.rst
index 531d56e31382..8f58c92bd2a1 100644
--- a/clang/docs/UndefinedBehaviorSanitizer.rst
+++ b/clang/docs/UndefinedBehaviorSanitizer.rst
@@ -148,11 +148,6 @@ Available checks are:
      Issues caught by this sanitizer are not undefined behavior,
      but are often unintentional.
   -  ``-fsanitize=integer-divide-by-zero``: Integer division by zero.
-  -  ``-fsanitize=implicit-bitfield-conversion``: Implicit conversion from
-     integer of larger bit width to smaller bitfield, if that results in data
-     loss. This includes unsigned/signed truncations and sign changes, similarly
-     to how the ``-fsanitize=implicit-integer-conversion`` group works, but
-     explicitly for bitfields.
   -  ``-fsanitize=nonnull-attribute``: Passing null pointer as a function
      parameter which is declared to never be null.
   -  ``-fsanitize=null``: Use of a null pointer or creation of a null
@@ -198,8 +193,8 @@ Available checks are:
      signed division overflow (``INT_MIN/-1``). Note that checks are still
      added even when ``-fwrapv`` is enabled. This sanitizer does not check for
      lossy implicit conversions performed before the computation (see
-     ``-fsanitize=implicit-integer-conversion``). Both of these two issues are handled
-     by ``-fsanitize=implicit-integer-conversion`` group of checks.
+     ``-fsanitize=implicit-conversion``). Both of these two issues are handled
+     by ``-fsanitize=implicit-conversion`` group of checks.
   -  ``-fsanitize=unreachable``: If control flow reaches an unreachable
      program point.
   -  ``-fsanitize=unsigned-integer-overflow``: Unsigned integer overflow, where
@@ -207,7 +202,7 @@ Available checks are:
      type. Unlike signed integer overflow, this is not undefined behavior, but
      it is often unintentional. This sanitizer does not check for lossy implicit
      conversions performed before such a computation
-     (see ``-fsanitize=implicit-integer-conversion``).
+     (see ``-fsanitize=implicit-conversion``).
   -  ``-fsanitize=vla-bound``: A variable-length array whose bound
      does not evaluate to a positive value.
   -  ``-fsanitize=vptr``: Use of an object whose vptr indicates that it is of
@@ -229,15 +224,11 @@ You can also use the following check groups:
   -  ``-fsanitize=implicit-integer-arithmetic-value-change``: Catches implicit
      conversions that change the arithmetic value of the integer. Enables
      ``implicit-signed-integer-truncation`` and ``implicit-integer-sign-change``.
-  -  ``-fsanitize=implicit-integer-conversion``: Checks for suspicious
-     behavior of implicit integer conversions. Enables
+  -  ``-fsanitize=implicit-conversion``: Checks for suspicious
+     behavior of implicit conversions. Enables
      ``implicit-unsigned-integer-truncation``,
      ``implicit-signed-integer-truncation``, and
      ``implicit-integer-sign-change``.
-  -  ``-fsanitize=implicit-conversion``: Checks for suspicious
-     behavior of implicit conversions. Enables
-     ``implicit-integer-conversion``, and
-     ``implicit-bitfield-conversion``.
   -  ``-fsanitize=integer``: Checks for undefined or suspicious integer
      behavior (e.g. unsigned integer overflow).
      Enables ``signed-integer-overflow``, ``unsigned-integer-overflow``,
diff --git a/clang/include/clang/Basic/Sanitizers.def b/clang/include/clang/Basic/Sanitizers.def
index b228ffd07ee7..c2137e3f61f6 100644
--- a/clang/include/clang/Basic/Sanitizers.def
+++ b/clang/include/clang/Basic/Sanitizers.def
@@ -163,24 +163,24 @@ SANITIZER_GROUP("implicit-integer-arithmetic-value-change",
                 ImplicitIntegerArithmeticValueChange,
                 ImplicitIntegerSignChange | ImplicitSignedIntegerTruncation)
 
-SANITIZER_GROUP("implicit-integer-conversion", ImplicitIntegerConversion,
-                ImplicitIntegerArithmeticValueChange |
-                    ImplicitUnsignedIntegerTruncation)
+SANITIZER("objc-cast", ObjCCast)
 
-// Implicit bitfield sanitizers
-SANITIZER("implicit-bitfield-conversion", ImplicitBitfieldConversion)
+// FIXME:
+//SANITIZER_GROUP("implicit-integer-conversion", ImplicitIntegerConversion,
+//                ImplicitIntegerArithmeticValueChange |
+//                    ImplicitUnsignedIntegerTruncation)
+//SANITIZER_GROUP("implicit-conversion", ImplicitConversion,
+//                ImplicitIntegerConversion)
 
 SANITIZER_GROUP("implicit-conversion", ImplicitConversion,
-                ImplicitIntegerConversion |
-                    ImplicitBitfieldConversion)
+                ImplicitIntegerArithmeticValueChange |
+                    ImplicitUnsignedIntegerTruncation)
 
 SANITIZER_GROUP("integer", Integer,
-                ImplicitIntegerConversion | IntegerDivideByZero | Shift |
+                ImplicitConversion | IntegerDivideByZero | Shift |
                     SignedIntegerOverflow | UnsignedIntegerOverflow |
                     UnsignedShiftBase)
 
-SANITIZER("objc-cast", ObjCCast)
-
 SANITIZER("local-bounds", LocalBounds)
 SANITIZER_GROUP("bounds", Bounds, ArrayBounds | LocalBounds)
 
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 0c7f48fe0060..54432353e742 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -5580,44 +5580,11 @@ LValue CodeGenFunction::EmitBinaryOperatorLValue(const BinaryOperator *E) {
       break;
     }
 
-    // TODO: Can we de-duplicate this code with the corresponding code in
-    // CGExprScalar, similar to the way EmitCompoundAssignmentLValue works?
-    RValue RV;
-    llvm::Value *Previous = nullptr;
-    QualType SrcType = E->getRHS()->getType();
-    // Check if LHS is a bitfield, if RHS contains an implicit cast expression
-    // we want to extract that value and potentially (if the bitfield sanitizer
-    // is enabled) use it to check for an implicit conversion.
-    if (E->getLHS()->refersToBitField()) {
-      llvm::Value *RHS =
-          EmitWithOriginalRHSBitfieldAssignment(E, Previous, &SrcType);
-      RV = RValue::get(RHS);
-    } else
-      RV = EmitAnyExpr(E->getRHS());
-
+    RValue RV = EmitAnyExpr(E->getRHS());
     LValue LV = EmitCheckedLValue(E->getLHS(), TCK_Store);
-
     if (RV.isScalar())
       EmitNullabilityCheck(LV, RV.getScalarVal(), E->getExprLoc());
-
-    if (LV.isBitField()) {
-      llvm::Value *Result = nullptr;
-      // If bitfield sanitizers are enabled we want to use the result
-      // to check whether a truncation or sign change has occurred.
-      if (SanOpts.has(SanitizerKind::ImplicitBitfieldConversion))
-        EmitStoreThroughBitfieldLValue(RV, LV, &Result);
-      else
-        EmitStoreThroughBitfieldLValue(RV, LV);
-
-      // If the expression contained an implicit conversion, make sure
-      // to use the value before the scalar conversion.
-      llvm::Value *Src = Previous ? Previous : RV.getScalarVal();
-      QualType DstType = E->getLHS()->getType();
-      EmitBitfieldConversionCheck(Src, SrcType, Result, DstType,
-                                  LV.getBitFieldInfo(), E->getExprLoc());
-    } else
-      EmitStoreThroughLValue(RV, LV);
-
+    EmitStoreThroughLValue(RV, LV);
     if (getLangOpts().OpenMP)
       CGM.getOpenMPRuntime().checkAndEmitLastprivateConditional(*this,
                                                                 E->getLHS());
diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index a4ab8a11b867..397b4977acc3 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -15,7 +15,6 @@
 #include "CGDebugInfo.h"
 #include "CGObjCRuntime.h"
 #include "CGOpenMPRuntime.h"
-#include "CGRecordLayout.h"
 #include "CodeGenFunction.h"
 #include "CodeGenModule.h"
 #include "ConstantEmitter.h"
@@ -309,7 +308,6 @@ public:
                                 llvm::Type *DstTy, SourceLocation Loc);
 
   /// Known implicit conversion check kinds.
-  /// This is used for bitfield conversion checks as well.
   /// Keep in sync with the enum of the same name in ubsan_handlers.h
   enum ImplicitConversionCheckKind : unsigned char {
     ICCK_IntegerTruncation = 0, // Legacy, was only used by clang 7.
@@ -1105,21 +1103,6 @@ void ScalarExprEmitter::EmitIntegerTruncationCheck(Value *Src, QualType SrcType,
                 {Src, Dst});
 }
 
-static llvm::Value *EmitIsNegativeTestHelper(Value *V, QualType VType,
-                                             const char *Name,
-                                             CGBuilderTy &Builder) {
-  bool VSigned = VType->isSignedIntegerOrEnumerationType();
-  llvm::Type *VTy = V->getType();
-  if (!VSigned) {
-    // If the value is unsigned, then it is never negative.
-    return llvm::ConstantInt::getFalse(VTy->getContext());
-  }
-  llvm::Constant *Zero = llvm::ConstantInt::get(VTy, 0);
-  return Builder.CreateICmp(llvm::ICmpInst::ICMP_SLT, V, Zero,
-                            llvm::Twine(Name) + "." + V->getName() +
-                                ".negativitycheck");
-}
-
 // Should be called within CodeGenFunction::SanitizerScope RAII scope.
 // Returns 'i1 false' when the conversion Src -> Dst changed the sign.
 static std::pair<ScalarExprEmitter::ImplicitConversionCheckKind,
@@ -1144,12 +1127,30 @@ EmitIntegerSignChangeCheckHelper(Value *Src, QualType SrcType, Value *Dst,
   assert(((SrcBits != DstBits) || (SrcSigned != DstSigned)) &&
          "either the widths should be different, or the signednesses.");
 
+  // NOTE: zero value is considered to be non-negative.
+  auto EmitIsNegativeTest = [&Builder](Value *V, QualType VType,
+                                       const char *Name) -> Value * {
+    // Is this value a signed type?
+    bool VSigned = VType->isSignedIntegerOrEnumerationType();
+    llvm::Type *VTy = V->getType();
+    if (!VSigned) {
+      // If the value is unsigned, then it is never negative.
+      // FIXME: can we encounter non-scalar VTy here?
+      return llvm::ConstantInt::getFalse(VTy->getContext());
+    }
+    // Get the zero of the same type with which we will be comparing.
+    llvm::Constant *Zero = llvm::ConstantInt::get(VTy, 0);
+    // %V.isnegative = icmp slt %V, 0
+    // I.e is %V *strictly* less than zero, does it have negative value?
+    return Builder.CreateICmp(llvm::ICmpInst::ICMP_SLT, V, Zero,
+                              llvm::Twine(Name) + "." + V->getName() +
+                                  ".negativitycheck");
+  };
+
   // 1. Was the old Value negative?
-  llvm::Value *SrcIsNegative =
-      EmitIsNegativeTestHelper(Src, SrcType, "src", Builder);
+  llvm::Value *SrcIsNegative = EmitIsNegativeTest(Src, SrcType, "src");
   // 2. Is the new Value negative?
-  llvm::Value *DstIsNegative =
-      EmitIsNegativeTestHelper(Dst, DstType, "dst", Builder);
+  llvm::Value *DstIsNegative = EmitIsNegativeTest(Dst, DstType, "dst");
   // 3. Now, was the 'negativity status' preserved during the conversion?
   //    NOTE: conversion from negative to zero is considered to change the sign.
   //    (We want to get 'false' when the conversion changed the sign)
@@ -1244,136 +1245,6 @@ void ScalarExprEmitter::EmitIntegerSignChangeCheck(Value *Src, QualType SrcType,
                 {Src, Dst});
 }
 
-// Should be called within CodeGenFunction::SanitizerScope RAII scope.
-// Returns 'i1 false' when the truncation Src -> Dst was lossy.
-static std::pair<ScalarExprEmitter::ImplicitConversionCheckKind,
-                 std::pair<llvm::Value *, SanitizerMask>>
-EmitBitfieldTruncationCheckHelper(Value *Src, QualType SrcType, Value *Dst,
-                                  QualType DstType, CGBuilderTy &Builder) {
-  bool SrcSigned = SrcType->isSignedIntegerOrEnumerationType();
-  bool DstSigned = DstType->isSignedIntegerOrEnumerationType();
-
-  ScalarExprEmitter::ImplicitConversionCheckKind Kind;
-  if (!SrcSigned && !DstSigned)
-    Kind = ScalarExprEmitter::ICCK_UnsignedIntegerTruncation;
-  else
-    Kind = ScalarExprEmitter::ICCK_SignedIntegerTruncation;
-
-  llvm::Value *Check = nullptr;
-  // 1. Extend the truncated value back to the same width as the Src.
-  Check = Builder.CreateIntCast(Dst, Src->getType(), DstSigned, "bf.anyext");
-  // 2. Equality-compare with the original source value
-  Check = Builder.CreateICmpEQ(Check, Src, "bf.truncheck");
-  // If the comparison result is 'i1 false', then the truncation was lossy.
-
-  return std::make_pair(
-      Kind, std::make_pair(Check, SanitizerKind::ImplicitBitfieldConversion));
-}
-
-// Should be called within CodeGenFunction::SanitizerScope RAII scope.
-// Returns 'i1 false' when the conversion Src -> Dst changed the sign.
-static std::pair<ScalarExprEmitter::ImplicitConversionCheckKind,
-                 std::pair<llvm::Value *, SanitizerMask>>
-EmitBitfieldSignChangeCheckHelper(Value *Src, QualType SrcType, Value *Dst,
-                                  QualType DstType, CGBuilderTy &Builder) {
-  // 1. Was the old Value negative?
-  llvm::Value *SrcIsNegative =
-      EmitIsNegativeTestHelper(Src, SrcType, "bf.src", Builder);
-  // 2. Is the new Value negative?
-  llvm::Value *DstIsNegative =
-      EmitIsNegativeTestHelper(Dst, DstType, "bf.dst", Builder);
-  // 3. Now, was the 'negativity status' preserved during the conversion?
-  //    NOTE: conversion from negative to zero is considered to change the sign.
-  //    (We want to get 'false' when the conversion changed the sign)
-  //    So we should just equality-compare the negativity statuses.
-  llvm::Value *Check = nullptr;
-  Check =
-      Builder.CreateICmpEQ(SrcIsNegative, DstIsNegative, "bf.signchangecheck");
-  // If the comparison result is 'false', then the conversion changed the sign.
-  return std::make_pair(
-      ScalarExprEmitter::ICCK_IntegerSignChange,
-      std::make_pair(Check, SanitizerKind::ImplicitBitfieldConversion));
-}
-
-void CodeGenFunction::EmitBitfieldConversionCheck(Value *Src, QualType SrcType,
-                                                  Value *Dst, QualType DstType,
-                                                  const CGBitFieldInfo &Info,
-                                                  SourceLocation Loc) {
-
-  if (!SanOpts.has(SanitizerKind::ImplicitBitfieldConversion))
-    return;
-
-  // We only care about int->int conversions here.
-  // We ignore conversions to/from pointer and/or bool.
-  if (!PromotionIsPotentiallyEligibleForImplicitIntegerConversionCheck(SrcType,
-                                                                       DstType))
-    return;
-
-  if (DstType->isBooleanType() || SrcType->isBooleanType())
-    return;
-
-  // This should be truncation of integral types.
-  assert(isa<llvm::IntegerType>(Src->getType()) &&
-         isa<llvm::IntegerType>(Dst->getType()) && "non-integer llvm type");
-
-  // TODO: Calculate src width to avoid emitting code
-  // for unecessary cases.
-  unsigned SrcBits = ConvertType(SrcType)->getScalarSizeInBits();
-  unsigned DstBits = Info.Size;
-
-  bool SrcSigned = SrcType->isSignedIntegerOrEnumerationType();
-  bool DstSigned = DstType->isSignedIntegerOrEnumerationType();
-
-  CodeGenFunction::SanitizerScope SanScope(this);
-
-  std::pair<ScalarExprEmitter::ImplicitConversionCheckKind,
-            std::pair<llvm::Value *, SanitizerMask>>
-      Check;
-
-  // Truncation
-  bool EmitTruncation = DstBits < SrcBits;
-  // If Dst is signed and Src unsigned, we want to be more specific
-  // about the CheckKind we emit, in this case we want to emit
-  // ICCK_SignedIntegerTruncationOrSignChange.
-  bool EmitTruncationFromUnsignedToSigned =
-      EmitTruncation && DstSigned && !SrcSigned;
-  // Sign change
-  bool SameTypeSameSize = SrcSigned == DstSigned && SrcBits == DstBits;
-  bool BothUnsigned = !SrcSigned && !DstSigned;
-  bool LargerSigned = (DstBits > SrcBits) && DstSigned;
-  // We can avoid emitting sign change checks in some obvious cases
-  //   1. If Src and Dst have the same signedness and size
-  //   2. If both are unsigned sign check is unecessary!
-  //   3. If Dst is signed and bigger than Src, either
-  //      sign-extension or zero-extension will make sure
-  //      the sign remains.
-  bool EmitSignChange = !SameTypeSameSize && !BothUnsigned && !LargerSigned;
-
-  if (EmitTruncation)
-    Check =
-        EmitBitfieldTruncationCheckHelper(Src, SrcType, Dst, DstType, Builder);
-  else if (EmitSignChange) {
-    assert(((SrcBits != DstBits) || (SrcSigned != DstSigned)) &&
-           "either the widths should be different, or the signednesses.");
-    Check =
-        EmitBitfieldSignChangeCheckHelper(Src, SrcType, Dst, DstType, Builder);
-  } else
-    return;
-
-  ScalarExprEmitter::ImplicitConversionCheckKind CheckKind = Check.first;
-  if (EmitTruncationFromUnsignedToSigned)
-    CheckKind = ScalarExprEmitter::ICCK_SignedIntegerTruncationOrSignChange;
-
-  llvm::Constant *StaticArgs[] = {
-      EmitCheckSourceLocation(Loc), EmitCheckTypeDescriptor(SrcType),
-      EmitCheckTypeDescriptor(DstType),
-      llvm::ConstantInt::get(Builder.getInt8Ty(), CheckKind),
-      llvm::ConstantInt::get(Builder.getInt32Ty(), Info.Size)};
-
-  EmitCheck(Check.second, SanitizerHandler::ImplicitConversion, StaticArgs,
-            {Src, Dst});
-}
-
 Value *ScalarExprEmitter::EmitScalarCast(Value *Src, QualType SrcType,
                                          QualType DstType, llvm::Type *SrcTy,
                                          llvm::Type *DstTy,
@@ -2749,8 +2620,6 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
   llvm::PHINode *atomicPHI = nullptr;
   llvm::Value *value;
   llvm::Value *input;
-  llvm::Value *Previous = nullptr;
-  QualType SrcType = E->getType();
 
   int amount = (isInc ? 1 : -1);
   bool isSubtraction = !isInc;
@@ -2839,8 +2708,7 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
              "base or promoted) will be signed, or the bitwidths will match.");
     }
     if (CGF.SanOpts.hasOneOf(
-            SanitizerKind::ImplicitIntegerArithmeticValueChange |
-            SanitizerKind::ImplicitBitfieldConversion) &&
+            SanitizerKind::ImplicitIntegerArithmeticValueChange) &&
         canPerformLossyDemotionCheck) {
       // While `x += 1` (for `x` with width less than int) is modeled as
       // promotion+arithmetics+demotion, and we can catch lossy demotion with
@@ -2851,26 +2719,13 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
       // the increment/decrement in the wider type, and finally
       // perform the demotion. This will catch lossy demotions.
 
-      // We have a special case for bitfields defined using all the bits of the
-      // type. In this case we need to do the same trick as for the integer
-      // sanitizer checks, i.e., promotion -> increment/decrement -> demotion.
-
       value = EmitScalarConversion(value, type, promotedType, E->getExprLoc());
       Value *amt = llvm::ConstantInt::get(value->getType(), amount, true);
       value = Builder.CreateAdd(value, amt, isInc ? "inc" : "dec");
       // Do pass non-default ScalarConversionOpts so that sanitizer check is
-      // emitted if LV is not a bitfield, otherwise the bitfield sanitizer
-      // checks will take care of the conversion.
-      ScalarConversionOpts Opts;
-      if (!LV.isBitField())
-        Opts = ScalarConversionOpts(CGF.SanOpts);
-      else if (CGF.SanOpts.has(SanitizerKind::ImplicitBitfieldConversion)) {
-        Previous = value;
-        SrcType = promotedType;
-      }
-
+      // emitted.
       value = EmitScalarConversion(value, promotedType, type, E->getExprLoc(),
-                                   Opts);
+                                   ScalarConversionOpts(CGF.SanOpts));
 
       // Note that signed integer inc/dec with width less than int can't
       // overflow because of promotion rules; we're just eliding a few steps
@@ -3055,12 +2910,9 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
   }
 
   // Store the updated result through the lvalue.
-  if (LV.isBitField()) {
-    Value *Src = Previous ? Previous : value;
+  if (LV.isBitField())
     CGF.EmitStoreThroughBitfieldLValue(RValue::get(value), LV, &value);
-    CGF.EmitBitfieldConversionCheck(Src, SrcType, value, E->getType(),
-                                    LV.getBitFieldInfo(), E->getExprLoc());
-  } else
+  else
     CGF.EmitStoreThroughLValue(RValue::get(value), LV);
 
   // If this is a postinc, return the value read from memory, otherwise use the
@@ -3565,15 +3417,8 @@ LValue ScalarExprEmitter::EmitCompoundAssignLValue(
 
   // Convert the result back to the LHS type,
   // potentially with Implicit Conversion sanitizer check.
-  // If LHSLV is a bitfield, use default ScalarConversionOpts
-  // to avoid emit any implicit integer checks.
-  Value *Previous = nullptr;
-  if (LHSLV.isBitField()) {
-    Previous = Result;
-    Result = EmitScalarConversion(Result, PromotionTypeCR, LHSTy, Loc);
-  } else
-    Result = EmitScalarConversion(Result, PromotionTypeCR, LHSTy, Loc,
-                                  ScalarConversionOpts(CGF.SanOpts));
+  Result = EmitScalarConversion(Result, PromotionTypeCR, LHSTy, Loc,
+                                ScalarConversionOpts(CGF.SanOpts));
 
   if (atomicPHI) {
     llvm::BasicBlock *curBlock = Builder.GetInsertBlock();
@@ -3592,14 +3437,9 @@ LValue ScalarExprEmitter::EmitCompoundAssignLValue(
   // specially because the result is altered by the store, i.e., [C99 6.5.16p1]
   // 'An assignment expression has the value of the left operand after the
   // assignment...'.
-  if (LHSLV.isBitField()) {
-    Value *Src = Previous ? Previous : Result;
-    QualType SrcType = E->getRHS()->getType();
-    QualType DstType = E->getLHS()->getType();
+  if (LHSLV.isBitField())
     CGF.EmitStoreThroughBitfieldLValue(RValue::get(Result), LHSLV, &Result);
-    CGF.EmitBitfieldConversionCheck(Src, SrcType, Result, DstType,
-                                    LHSLV.getBitFieldInfo(), E->getExprLoc());
-  } else
+  else
     CGF.EmitStoreThroughLValue(RValue::get(Result), LHSLV);
 
   if (CGF.getLangOpts().OpenMP)
@@ -4711,24 +4551,6 @@ Value *ScalarExprEmitter::EmitCompare(const BinaryOperator *E,
                               E->getExprLoc());
 }
 
-llvm::Value *CodeGenFunction::EmitWithOriginalRHSBitfieldAssignment(
-    const BinaryOperator *E, Value *Previous, QualType *SrcType) {
-  // In case we have the integer or bitfield sanitizer checks enabled
-  // we want to get the expression before scalar conversion.
-  if (auto *ICE = dyn_cast<ImplicitCastExpr>(E->getRHS())) {
-    CastKind Kind = ICE->getCastKind();
-    if (Kind == CK_IntegralCast) {
-      *SrcType = ICE->getSubExpr()->getType();
-      Previous = EmitScalarExpr(ICE->getSubExpr());
-      // Pass default ScalarConversionOpts to avoid emitting
-      // integer sanitizer checks as E refers to bitfield.
-      return EmitScalarConversion(Previous, *SrcType, ICE->getType(),
-                                  ICE->getExprLoc());
-    }
-  }
-  return EmitScalarExpr(E->getRHS());
-}
-
 Value *ScalarExprEmitter::VisitBinAssign(const BinaryOperator *E) {
   bool Ignore = TestAndClearIgnoreResultAssign();
 
@@ -4757,16 +4579,7 @@ Value *ScalarExprEmitter::VisitBinAssign(const BinaryOperator *E) {
   case Qualifiers::OCL_None:
     // __block variables need to have the rhs evaluated first, plus
     // this should improve codegen just a little.
-    Value *Previous = nullptr;
-    QualType SrcType = E->getRHS()->getType();
-    // Check if LHS is a bitfield, if RHS contains an implicit cast expression
-    // we want to extract that value and potentially (if the bitfield sanitizer
-    // is enabled) use it to check for an implicit conversion.
-    if (E->getLHS()->refersToBitField())
-      RHS = CGF.EmitWithOriginalRHSBitfieldAssignment(E, Previous, &SrcType);
-    else
-      RHS = Visit(E->getRHS());
-
+    RHS = Visit(E->getRHS());
     LHS = EmitCheckedLValue(E->getLHS(), CodeGenFunction::TCK_Store);
 
     // Store the value into the LHS.  Bit-fields are handled specially
@@ -4775,12 +4588,6 @@ Value *ScalarExprEmitter::VisitBinAssign(const BinaryOperator *E) {
     // the assignment...'.
     if (LHS.isBitField()) {
       CGF.EmitStoreThroughBitfieldLValue(RValue::get(RHS), LHS, &RHS);
-      // If the expression contained an implicit conversion, make sure
-      // to use the value before the scalar conversion.
-      Value *Src = Previous ? Previous : RHS;
-      QualType DstType = E->getLHS()->getType();
-      CGF.EmitBitfieldConversionCheck(Src, SrcType, RHS, DstType,
-                                      LHS.getBitFieldInfo(), E->getExprLoc());
     } else {
       CGF.EmitNullabilityCheck(LHS, RHS, E->getExprLoc());
       CGF.EmitStoreThroughLValue(RValue::get(RHS), LHS);
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 99a7f518730e..e2a7e28c8211 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -2786,21 +2786,6 @@ public:
   /// expression and compare the result against zero, returning an Int1Ty value.
   llvm::Value *EvaluateExprAsBool(const Expr *E);
 
-  /// Retrieve the implicit cast expression of the rhs in a binary operator
-  /// expression by passing pointers to Value and QualType
-  /// This is used for implicit bitfield conversion checks, which
-  /// must compare with the value before potential truncation.
-  llvm::Value *EmitWithOriginalRHSBitfieldAssignment(const BinaryOperator *E,
-                                                     llvm::Value *Previous,
-                                                     QualType *SrcType);
-
-  /// Emit a check that an [implicit] conversion of a bitfield. It is not UB,
-  /// so we use the value after conversion.
-  void EmitBitfieldConversionCheck(llvm::Value *Src, QualType SrcType,
-                                   llvm::Value *Dst, QualType DstType,
-                                   const CGBitFieldInfo &Info,
-                                   SourceLocation Loc);
-
   /// EmitIgnoredExpr - Emit an expression in a context which ignores the result.
   void EmitIgnoredExpr(const Expr *E);
 
diff --git a/clang/test/CodeGen/ubsan-bitfield-conversion.c b/clang/test/CodeGen/ubsan-bitfield-conversion.c
deleted file mode 100644
index ea9bdd7da6bc..000000000000
--- a/clang/test/CodeGen/ubsan-bitfield-conversion.c
+++ /dev/null
@@ -1,61 +0,0 @@
-// RUN: %clang -fsanitize=implicit-bitfield-conversion -target x86_64-linux -S -emit-llvm -o - %s | FileCheck %s --check-prefixes=CHECK,CHECK-BITFIELD-CONVERSION
-// RUN: %clang -fsanitize=implicit-integer-conversion -target x86_64-linux -S -emit-llvm -o - %s | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -fsanitize=implicit-conversion -target x86_64-linux -S -emit-llvm -o - %s | FileCheck %s --check-prefixes=CHECK,CHECK-BITFIELD-CONVERSION
-
-typedef struct _xx {
-  int x1:3;
-  char x2:2;
-} xx, *pxx;
-
-xx vxx;
-
-// CHECK-LABEL: define{{.*}} void @foo1
-void foo1(int x) {
-  vxx.x1 = x;
-  // CHECK: store i8 %{{.*}}
-  // CHECK-NEXT: [[BFRESULTSHL:%.*]] = shl i8 {{.*}}, 5
-  // CHECK-NEXT: [[BFRESULTASHR:%.*]] = ashr i8 [[BFRESULTSHL]], 5
-  // CHECK-NEXT: [[BFRESULTCAST:%.*]] = sext i8 [[BFRESULTASHR]] to i32
-  // CHECK-BITFIELD-CONVERSION: call void @__ubsan_handle_implicit_conversion
-  // CHECK-BITFIELD-CONVERSION-NEXT: br label %[[CONT:.*]], !nosanitize !6
-  // CHECK-BITFIELD-CONVERSION: [[CONT]]:
-  // CHECK-NEXT: ret void
-}
-
-// CHECK-LABEL: define{{.*}} void @foo2
-void foo2(int x) {
-  vxx.x2 = x;
-  // CHECK: store i8 %{{.*}}
-  // CHECK-NEXT: [[BFRESULTSHL:%.*]] = shl i8 {{.*}}, 6
-  // CHECK-NEXT: [[BFRESULTASHR:%.*]] = ashr i8 [[BFRESULTSHL]], 6
-  // CHECK-BITFIELD-CONVERSION: call void @__ubsan_handle_implicit_conversion
-  // CHECK-BITFIELD-CONVERSION-NEXT: br label %[[CONT:.*]], !nosanitize !6
-  // CHECK-BITFIELD-CONVERSION: [[CONT]]:
-  // CHECK-NEXT: ret void
-}
-
-// CHECK-LABEL: define{{.*}} void @foo3
-void foo3() {
-  vxx.x1++;
-  // CHECK: store i8 %{{.*}}
-  // CHECK-NEXT: [[BFRESULTSHL:%.*]] = shl i8 {{.*}}, 5
-  // CHECK-NEXT: [[BFRESULTASHR:%.*]] = ashr i8 [[BFRESULTSHL]], 5
-  // CHECK-NEXT: [[BFRESULTCAST:%.*]] = sext i8 [[BFRESULTASHR]] to i32
-  // CHECK-BITFIELD-CONVERSION: call void @__ubsan_handle_implicit_conversion
-  // CHECK-BITFIELD-CONVERSION-NEXT: br label %[[CONT:.*]], !nosanitize !6
-  // CHECK-BITFIELD-CONVERSION: [[CONT]]:
-  // CHECK-NEXT: ret void
-}
-
-// CHECK-LABEL: define{{.*}} void @foo4
-void foo4(int x) {
-  vxx.x1 += x;
-  // CHECK: store i8 %{{.*}}
-  // CHECK-NEXT: [[BFRESULTSHL:%.*]] = shl i8 {{.*}}, 5
-  // CHECK-NEXT: [[BFRESULTASHR:%.*]] = ashr i8 [[BFRESULTSHL]], 5
-  // CHECK-NEXT: [[BFRESULTCAST:%.*]] = sext i8 [[BFRESULTASHR]] to i32
-  // CHECK-BITFIELD-CONVERSION: call void @__ubsan_handle_implicit_conversion
-  // CHECK-BITFIELD-CONVERSION-NEXT: br label %[[CONT:.*]], !nosanitize !6
-  // CHECK-BITFIELD-CONVERSION: [[CONT]]:
-  // CHECK-NEXT: ret void
-}
\ No newline at end of file
diff --git a/clang/test/CodeGenCXX/ubsan-bitfield-conversion.cpp b/clang/test/CodeGenCXX/ubsan-bitfield-conversion.cpp
deleted file mode 100644
index 92f6e247c5f5..000000000000
--- a/clang/test/CodeGenCXX/ubsan-bitfield-conversion.cpp
+++ /dev/null
@@ -1,94 +0,0 @@
-// RUN: %clang -x c++ -fsanitize=implicit-bitfield-conversion -target x86_64-linux -S -emit-llvm -o - %s | FileCheck %s --check-prefixes=CHECK,CHECK-BITFIELD-CONVERSION
-// RUN: %clang -x c++ -fsanitize=implicit-integer-conversion -target x86_64-linux -S -emit-llvm -o - %s | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -x c++ -fsanitize=implicit-conversion -target x86_64-linux -S -emit-llvm -o - %s | FileCheck %s --check-prefixes=CHECK,CHECK-BITFIELD-CONVERSION
-
-struct S {
-  int a:3;
-  char b:2;
-};
-
-class C : public S {
-  public:
-    short c:3;
-};
-
-S s;
-C c;
-
-// CHECK-LABEL: define{{.*}} void @{{.*foo1.*}}
-void foo1(int x) {
-  s.a = x;
-  // CHECK: store i8 %{{.*}}
-  // CHECK-BITFIELD-CONVERSION: [[BFRESULTSHL:%.*]] = shl i8 {{.*}}, 5
-  // CHECK-BITFIELD-CONVERSION-NEXT: [[BFRESULTASHR:%.*]] = ashr i8 [[BFRESULTSHL]], 5
-  // CHECK-BITFIELD-CONVERSION-NEXT: [[BFRESULTCAST:%.*]] = sext i8 [[BFRESULTASHR]] to i32
-  // CHECK-BITFIELD-CONVERSION: call void @__ubsan_handle_implicit_conversion
-  // CHECK-BITFIELD-CONVERSION-NEXT: br label %[[CONT:.*]], !nosanitize !6
-  c.a = x;
-  // CHECK: store i8 %{{.*}}
-  // CHECK-BITFIELD-CONVERSION: [[BFRESULTSHL:%.*]] = shl i8 {{.*}}, 5
-  // CHECK-BITFIELD-CONVERSION-NEXT: [[BFRESULTASHR:%.*]] = ashr i8 [[BFRESULTSHL]], 5
-  // CHECK-BITFIELD-CONVERSION-NEXT: [[BFRESULTCAST:%.*]] = sext i8 [[BFRESULTASHR]] to i32
-  // CHECK-BITFIELD-CONVERSION: call void @__ubsan_handle_implicit_conversion
-  // CHECK-BITFIELD-CONVERSION-NEXT: br label %[[CONT:.*]], !nosanitize !6
-  // CHECK-BITFIELD-CONVERSION: [[CONT]]:
-  // CHECK-NEXT: ret void
-}
-
-// CHECK-LABEL: define{{.*}} void @{{.*foo2.*}}
-void foo2(int x) {
-  s.b = x;
-  // CHECK: store i8 %{{.*}}
-  // CHECK-BITFIELD-CONVERSION: [[BFRESULTSHL:%.*]] = shl i8 {{.*}}, 6
-  // CHECK-BITFIELD-CONVERSION-NEXT: [[BFRESULTASHR:%.*]] = ashr i8 [[BFRESULTSHL]], 6
-  // CHECK-BITFIELD-CONVERSION: call void @__ubsan_handle_implicit_conversion
-  // CHECK-BITFIELD-CONVERSION-NEXT: br label %[[CONT:.*]], !nosanitize !6
-  c.b = x;
-  // CHECK: store i8 %{{.*}}
-  // CHECK-BITFIELD-CONVERSION: [[BFRESULTSHL:%.*]] = shl i8 {{.*}}, 6
-  // CHECK-BITFIELD-CONVERSION-NEXT: [[BFRESULTASHR:%.*]] = ashr i8 [[BFRESULTSHL]], 6
-  // CHECK-BITFIELD-CONVERSION: call void @__ubsan_handle_implicit_conversion
-  // CHECK-BITFIELD-CONVERSION-NEXT: br label %[[CONT:.*]], !nosanitize !6
-  // CHECK-BITFIELD-CONVERSION: [[CONT]]:
-  // CHECK-NEXT: ret void
-}
-
-// CHECK-LABEL: define{{.*}} void @{{.*foo3.*}}
-void foo3() {
-  s.a++;
-  // CHECK: store i8 %{{.*}}
-  // CHECK-NEXT: [[BFRESULTSHL:%.*]] = shl i8 {{.*}}, 5
-  // CHECK-NEXT: [[BFRESULTASHR:%.*]] = ashr i8 [[BFRESULTSHL]], 5
-  // CHECK-NEXT: [[BFRESULTCAST:%.*]] = sext i8 [[BFRESULTASHR]] to i32
-  // CHECK-BITFIELD-CONVERSION: call void @__ubsan_handle_implicit_conversion
-  // CHECK-BITFIELD-CONVERSION-NEXT: br label %[[CONT:.*]], !nosanitize !6
-  c.a++;
-  // CHECK: store i8 %{{.*}}
-  // CHECK-NEXT: [[BFRESULTSHL:%.*]] = shl i8 {{.*}}, 5
-  // CHECK-NEXT: [[BFRESULTASHR:%.*]] = ashr i8 [[BFRESULTSHL]], 5
-  // CHECK-NEXT: [[BFRESULTCAST:%.*]] = sext i8 [[BFRESULTASHR]] to i32
-  // CHECK-BITFIELD-CONVERSION: call void @__ubsan_handle_implicit_conversion
-  // CHECK-BITFIELD-CONVERSION-NEXT: br label %[[CONT:.*]], !nosanitize !6
-  // CHECK-BITFIELD-CONVERSION: [[CONT]]:
-  // CHECK-NEXT: ret void
-}
-
-// CHECK-LABEL: define{{.*}} void @{{.*foo4.*}}
-void foo4(int x) {
-  s.a += x;
-  // CHECK: store i8 %{{.*}}
-  // CHECK-NEXT: [[BFRESULTSHL:%.*]] = shl i8 {{.*}}, 5
-  // CHECK-NEXT: [[BFRESULTASHR:%.*]] = ashr i8 [[BFRESULTSHL]], 5
-  // CHECK-NEXT: [[BFRESULTCAST:%.*]] = sext i8 [[BFRESULTASHR]] to i32
-  // CHECK-BITFIELD-CONVERSION: call void @__ubsan_handle_implicit_conversion
-  // CHECK-BITFIELD-CONVERSION-NEXT: br label %[[CONT:.*]], !nosanitize !6
-  c.a += x;
-  // CHECK: store i8 %{{.*}}
-  // CHECK-NEXT: [[BFRESULTSHL:%.*]] = shl i8 {{.*}}, 5
-  // CHECK-NEXT: [[BFRESULTASHR:%.*]] = ashr i8 [[BFRESULTSHL]], 5
-  // CHECK-NEXT: [[BFRESULTCAST:%.*]] = sext i8 [[BFRESULTASHR]] to i32
-  // CHECK-BITFIELD-CONVERSION: call void @__ubsan_handle_implicit_conversion
-  // CHECK-BITFIELD-CONVERSION-NEXT: br label %[[CONT:.*]], !nosanitize !6
-  // CHECK-BITFIELD-CONVERSION: [[CONT]]:
-  // CHECK-NEXT: ret void
-}
\ No newline at end of file
diff --git a/clang/test/Driver/fsanitize.c b/clang/test/Driver/fsanitize.c
index 571f79a6e7f7..1671825042c3 100644
--- a/clang/test/Driver/fsanitize.c
+++ b/clang/test/Driver/fsanitize.c
@@ -35,20 +35,20 @@
 // RUN: %clang --target=%itanium_abi_triple -fsanitize=integer %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-INTEGER -implicit-check-not="-fsanitize-address-use-after-scope"
 // CHECK-INTEGER: "-fsanitize={{((signed-integer-overflow|unsigned-integer-overflow|integer-divide-by-zero|shift-base|shift-exponent|implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change|unsigned-shift-base),?){9}"}}
 
-// RUN: %clang -fsanitize=implicit-integer-conversion %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-integer-conversion,CHECK-implicit-integer-conversion-RECOVER
-// RUN: %clang -fsanitize=implicit-integer-conversion -fsanitize-recover=implicit-integer-conversion %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-integer-conversion,CHECK-implicit-integer-conversion-RECOVER
-// RUN: %clang -fsanitize=implicit-integer-conversion -fno-sanitize-recover=implicit-integer-conversion %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-integer-conversion,CHECK-implicit-integer-conversion-NORECOVER
-// RUN: %clang -fsanitize=implicit-integer-conversion -fsanitize-trap=implicit-integer-conversion %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-integer-conversion,CHECK-implicit-integer-conversion-TRAP
-// CHECK-implicit-integer-conversion: "-fsanitize={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
-// CHECK-implicit-integer-conversion-RECOVER: "-fsanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
-// CHECK-implicit-integer-conversion-RECOVER-NOT: "-fno-sanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
-// CHECK-implicit-integer-conversion-RECOVER-NOT: "-fsanitize-trap={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
-// CHECK-implicit-integer-conversion-NORECOVER-NOT: "-fno-sanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}} // ???
-// CHECK-implicit-integer-conversion-NORECOVER-NOT: "-fsanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
-// CHECK-implicit-integer-conversion-NORECOVER-NOT: "-fsanitize-trap={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
-// CHECK-implicit-integer-conversion-TRAP: "-fsanitize-trap={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
-// CHECK-implicit-integer-conversion-TRAP-NOT: "-fsanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
-// CHECK-implicit-integer-conversion-TRAP-NOT: "-fno-sanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
+// RUN: %clang -fsanitize=implicit-conversion %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-conversion,CHECK-implicit-conversion-RECOVER
+// RUN: %clang -fsanitize=implicit-conversion -fsanitize-recover=implicit-conversion %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-conversion,CHECK-implicit-conversion-RECOVER
+// RUN: %clang -fsanitize=implicit-conversion -fno-sanitize-recover=implicit-conversion %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-conversion,CHECK-implicit-conversion-NORECOVER
+// RUN: %clang -fsanitize=implicit-conversion -fsanitize-trap=implicit-conversion %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-conversion,CHECK-implicit-conversion-TRAP
+// CHECK-implicit-conversion: "-fsanitize={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
+// CHECK-implicit-conversion-RECOVER: "-fsanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
+// CHECK-implicit-conversion-RECOVER-NOT: "-fno-sanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
+// CHECK-implicit-conversion-RECOVER-NOT: "-fsanitize-trap={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
+// CHECK-implicit-conversion-NORECOVER-NOT: "-fno-sanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}} // ???
+// CHECK-implicit-conversion-NORECOVER-NOT: "-fsanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
+// CHECK-implicit-conversion-NORECOVER-NOT: "-fsanitize-trap={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
+// CHECK-implicit-conversion-TRAP: "-fsanitize-trap={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
+// CHECK-implicit-conversion-TRAP-NOT: "-fsanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
+// CHECK-implicit-conversion-TRAP-NOT: "-fno-sanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation|implicit-integer-sign-change),?){3}"}}
 
 // RUN: %clang -fsanitize=implicit-integer-arithmetic-value-change %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-integer-arithmetic-value-change,CHECK-implicit-integer-arithmetic-value-change-RECOVER
 // RUN: %clang -fsanitize=implicit-integer-arithmetic-value-change -fsanitize-recover=implicit-integer-arithmetic-value-change %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-integer-arithmetic-value-change,CHECK-implicit-integer-arithmetic-value-change-RECOVER
diff --git a/compiler-rt/lib/ubsan/ubsan_handlers.cpp b/compiler-rt/lib/ubsan/ubsan_handlers.cpp
index 27d01653f088..0f16507d5d88 100644
--- a/compiler-rt/lib/ubsan/ubsan_handlers.cpp
+++ b/compiler-rt/lib/ubsan/ubsan_handlers.cpp
@@ -555,11 +555,13 @@ static void handleImplicitConversion(ImplicitConversionData *Data,
                                      ReportOptions Opts, ValueHandle Src,
                                      ValueHandle Dst) {
   SourceLocation Loc = Data->Loc.acquire();
+  ErrorType ET = ErrorType::GenericUB;
+
   const TypeDescriptor &SrcTy = Data->FromType;
   const TypeDescriptor &DstTy = Data->ToType;
+
   bool SrcSigned = SrcTy.isSignedIntegerTy();
   bool DstSigned = DstTy.isSignedIntegerTy();
-  ErrorType ET = ErrorType::GenericUB;
 
   switch (Data->Kind) {
   case ICCK_IntegerTruncation: { // Legacy, no longer used.
@@ -592,23 +594,14 @@ static void handleImplicitConversion(ImplicitConversionData *Data,
 
   ScopedReport R(Opts, Loc, ET);
 
-  // In the case we have a bitfield, we want to explicitly say so in the
-  // error message.
   // FIXME: is it possible to dump the values as hex with fixed width?
-  if (Data->BitfieldBits)
-    Diag(Loc, DL_Error, ET,
-         "implicit conversion from type %0 of value %1 (%2-bit, %3signed) to "
-         "type %4 changed the value to %5 (%6-bit bitfield, %7signed)")
-        << SrcTy << Value(SrcTy, Src) << SrcTy.getIntegerBitWidth()
-        << (SrcSigned ? "" : "un") << DstTy << Value(DstTy, Dst)
-        << Data->BitfieldBits << (DstSigned ? "" : "un");
-  else
-    Diag(Loc, DL_Error, ET,
-         "implicit conversion from type %0 of value %1 (%2-bit, %3signed) to "
-         "type %4 changed the value to %5 (%6-bit, %7signed)")
-        << SrcTy << Value(SrcTy, Src) << SrcTy.getIntegerBitWidth()
-        << (SrcSigned ? "" : "un") << DstTy << Value(DstTy, Dst)
-        << DstTy.getIntegerBitWidth() << (DstSigned ? "" : "un");
+
+  Diag(Loc, DL_Error, ET,
+       "implicit conversion from type %0 of value %1 (%2-bit, %3signed) to "
+       "type %4 changed the value to %5 (%6-bit, %7signed)")
+      << SrcTy << Value(SrcTy, Src) << SrcTy.getIntegerBitWidth()
+      << (SrcSigned ? "" : "un") << DstTy << Value(DstTy, Dst)
+      << DstTy.getIntegerBitWidth() << (DstSigned ? "" : "un");
 }
 
 void __ubsan::__ubsan_handle_implicit_conversion(ImplicitConversionData *Data,
diff --git a/compiler-rt/lib/ubsan/ubsan_handlers.h b/compiler-rt/lib/ubsan/ubsan_handlers.h
index bae661a56833..3bd5046de3d7 100644
--- a/compiler-rt/lib/ubsan/ubsan_handlers.h
+++ b/compiler-rt/lib/ubsan/ubsan_handlers.h
@@ -147,7 +147,6 @@ struct ImplicitConversionData {
   const TypeDescriptor &FromType;
   const TypeDescriptor &ToType;
   /* ImplicitConversionCheckKind */ unsigned char Kind;
-  unsigned int BitfieldBits;
 };
 
 /// \brief Implict conversion that changed the value.