Append options for floating-point commutivity when related diagnostics are produced.

With this patch clang appends the command line options that would allow vectorization when floating-point commutativity is required. Specifically those are enabling fast-math or specifying a loop hint. 


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@244492 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 35 insertions, 0 deletions

diff --git a/include/clang/Basic/DiagnosticFrontendKinds.td b/include/clang/Basic/DiagnosticFrontendKinds.td
index 21058aa0bb..080c7381b5 100644
--- a/include/clang/Basic/DiagnosticFrontendKinds.td
+++ b/include/clang/Basic/DiagnosticFrontendKinds.td
@@ -45,6 +45,10 @@ def remark_fe_backend_optimization_remark_missed : Remark<"%0">, BackendInfo,
     InGroup<BackendOptimizationRemarkMissed>;
 def remark_fe_backend_optimization_remark_analysis : Remark<"%0">, BackendInfo,
     InGroup<BackendOptimizationRemarkAnalysis>;
+def remark_fe_backend_optimization_remark_analysis_fpcommute : Remark<"%0; "
+    "allow commutativity by specifying ‘#pragma clang loop vectorize(enable)’ "
+    "before the loop or by providing the compiler option ‘-ffast-math’">,
+    BackendInfo, InGroup<BackendOptimizationRemarkAnalysis>;
 def warn_fe_backend_optimization_failure : Warning<"%0">, BackendInfo,
     InGroup<BackendOptimizationFailure>, DefaultWarn;
 def note_fe_backend_optimization_remark_invalid_loc : Note<"could "
diff --git a/lib/CodeGen/CodeGenAction.cpp b/lib/CodeGen/CodeGenAction.cpp
index d97a64ec24..d47997e231 100644
--- a/lib/CodeGen/CodeGenAction.cpp
+++ b/lib/CodeGen/CodeGenAction.cpp
@@ -256,6 +256,8 @@ namespace clang {
         const llvm::DiagnosticInfoOptimizationRemarkMissed &D);
     void OptimizationRemarkHandler(
         const llvm::DiagnosticInfoOptimizationRemarkAnalysis &D);
+    void OptimizationRemarkHandler(
+        const llvm::DiagnosticInfoOptimizationRemarkAnalysisFPCommute &D);
     void OptimizationFailureHandler(
         const llvm::DiagnosticInfoOptimizationFailure &D);
   };
@@ -500,6 +502,17 @@ void BackendConsumer::OptimizationRemarkHandler(
         D, diag::remark_fe_backend_optimization_remark_analysis);
 }
 
+void BackendConsumer::OptimizationRemarkHandler(
+    const llvm::DiagnosticInfoOptimizationRemarkAnalysisFPCommute &D) {
+  // Optimization analysis remarks are active only if the -Rpass-analysis
+  // flag has a regular expression that matches the name of the pass
+  // name in \p D.
+  if (CodeGenOpts.OptimizationRemarkAnalysisPattern &&
+      CodeGenOpts.OptimizationRemarkAnalysisPattern->match(D.getPassName()))
+    EmitOptimizationMessage(
+        D, diag::remark_fe_backend_optimization_remark_analysis_fpcommute);
+}
+
 void BackendConsumer::OptimizationFailureHandler(
     const llvm::DiagnosticInfoOptimizationFailure &D) {
   EmitOptimizationMessage(D, diag::warn_fe_backend_optimization_failure);
@@ -553,6 +566,12 @@ void BackendConsumer::DiagnosticHandlerImpl(const DiagnosticInfo &DI) {
     OptimizationRemarkHandler(
         cast<DiagnosticInfoOptimizationRemarkAnalysis>(DI));
     return;
+  case llvm::DK_OptimizationRemarkAnalysisFPCommute:
+    // Optimization remarks are always handled completely by this
+    // handler. There is no generic way of emitting them.
+    OptimizationRemarkHandler(
+        cast<DiagnosticInfoOptimizationRemarkAnalysisFPCommute>(DI));
+    return;
   case llvm::DK_OptimizationFailure:
     // Optimization failures are always handled completely by this
     // handler.
diff --git a/test/Frontend/optimization-remark-options.c b/test/Frontend/optimization-remark-options.c
new file mode 100644
index 0000000000..33cc9e015a
--- /dev/null
+++ b/test/Frontend/optimization-remark-options.c
@@ -0,0 +1,12 @@
+// RUN: %clang -O1 -fvectorize -Rpass-analysis=loop-vectorize -emit-llvm -S %s -o - 2>&1 | FileCheck %s
+
+// CHECK: {{.*}}:9:11: remark: loop not vectorized: vectorization requires changes in the order of operations, however IEEE 754 floating-point operations are not commutative; allow commutativity by specifying ‘#pragma clang loop vectorize(enable)’ before the loop or by providing the compiler option ‘-ffast-math’
+
+double foo(int N) {
+  double v = 0.0;
+
+  for (int i = 0; i < N; i++)
+    v = v + 1.0;
+
+  return v;
+}