From 6a36a695bab036e07052f471fd96d15042f0a7ed Mon Sep 17 00:00:00 2001 From: Hans Wennborg Date: Mon, 23 Jan 2017 17:55:50 +0000 Subject: Merging r292555, r292558 and r292559: ------------------------------------------------------------------------ r292555 | rsmith | 2017-01-19 16:45:35 -0800 (Thu, 19 Jan 2017) | 6 lines P0426: Make the library implementation of constexpr char_traits a little easier by providing a memchr builtin that returns char* instead of void*. Also add a __has_feature flag to indicate the presence of constexpr forms of the relevant functions. ------------------------------------------------------------------------ ------------------------------------------------------------------------ r292558 | rsmith | 2017-01-19 16:57:59 -0800 (Thu, 19 Jan 2017) | 2 lines Add documentation for constexpr string builtin support. ------------------------------------------------------------------------ ------------------------------------------------------------------------ r292559 | rsmith | 2017-01-19 17:08:15 -0800 (Thu, 19 Jan 2017) | 2 lines Fix documentation typo. ------------------------------------------------------------------------ git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_40@292807 91177308-0d34-0410-b5e6-96231b3b80d8 --- docs/LanguageExtensions.rst | 40 +++++++++++++++++++++++++++++++++++++++ include/clang/Basic/Builtins.def | 1 + lib/AST/ExprConstant.cpp | 2 ++ lib/CodeGen/CGBuiltin.cpp | 4 ++++ lib/Lex/PPMacroExpansion.cpp | 1 + test/CodeGenCXX/builtins.cpp | 4 ++++ test/Lexer/has_feature_cxx0x.cpp | 11 +++++++++++ test/SemaCXX/constexpr-string.cpp | 21 ++++++++++++++++++++ 8 files changed, 84 insertions(+) diff --git a/docs/LanguageExtensions.rst b/docs/LanguageExtensions.rst index 64e6ffb7f3..885ad579ba 100644 --- a/docs/LanguageExtensions.rst +++ b/docs/LanguageExtensions.rst @@ -1776,6 +1776,46 @@ numeric primitives such as frexp. See `LLVM canonicalize intrinsic `_ for more information on the semantics. +String builtins +--------------- + +Clang provides constant expression evaluation support for builtins forms of +the following functions from the C standard library ```` header: + +* ``memchr`` +* ``memcmp`` +* ``strchr`` +* ``strcmp`` +* ``strlen`` +* ``strncmp`` +* ``wcschr`` +* ``wcscmp`` +* ``wcslen`` +* ``wcsncmp`` +* ``wmemchr`` +* ``wmemcmp`` + +In each case, the builtin form has the name of the C library function prefixed +by ``__builtin_``. Example: + +.. code-block:: c + + void *p = __builtin_memchr("foobar", 'b', 5); + +In addition to the above, one further builtin is provided: + +.. code-block:: c + + char *__builtin_char_memchr(const char *haystack, int needle, size_t size); + +``__builtin_char_memchr(a, b, c)`` is identical to +``(char*)__builtin_memchr(a, b, c)`` except that its use is permitted within +constant expressions in C++11 onwards (where a cast from ``void*`` to ``char*`` +is disallowed in general). + +Support for constant expression evaluation for the above builtins be detected +with ``__has_feature(cxx_constexpr_string_builtins)``. + .. _langext-__c11_atomic: __c11_atomic builtins diff --git a/include/clang/Basic/Builtins.def b/include/clang/Basic/Builtins.def index ec0a2796ec..326a8fa663 100644 --- a/include/clang/Basic/Builtins.def +++ b/include/clang/Basic/Builtins.def @@ -1339,6 +1339,7 @@ BUILTIN(__builtin_smulll_overflow, "bSLLiCSLLiCSLLi*", "n") BUILTIN(__builtin_addressof, "v*v&", "nct") BUILTIN(__builtin_operator_new, "v*z", "c") BUILTIN(__builtin_operator_delete, "vv*", "n") +BUILTIN(__builtin_char_memchr, "c*cC*iz", "n") // Safestack builtins BUILTIN(__builtin___get_unsafe_stack_start, "v*", "Fn") diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp index a8512b2940..5fab58a5af 100644 --- a/lib/AST/ExprConstant.cpp +++ b/lib/AST/ExprConstant.cpp @@ -5683,6 +5683,7 @@ bool PointerExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E, case Builtin::BI__builtin_strchr: case Builtin::BI__builtin_wcschr: case Builtin::BI__builtin_memchr: + case Builtin::BI__builtin_char_memchr: case Builtin::BI__builtin_wmemchr: { if (!Visit(E->getArg(0))) return false; @@ -5720,6 +5721,7 @@ bool PointerExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E, // Fall through. case Builtin::BImemchr: case Builtin::BI__builtin_memchr: + case Builtin::BI__builtin_char_memchr: // memchr compares by converting both sides to unsigned char. That's also // correct for strchr if we get this far (to cope with plain char being // unsigned in the strchr case). diff --git a/lib/CodeGen/CGBuiltin.cpp b/lib/CodeGen/CGBuiltin.cpp index 2ede1d46b3..b3d02f1f51 100644 --- a/lib/CodeGen/CGBuiltin.cpp +++ b/lib/CodeGen/CGBuiltin.cpp @@ -1189,6 +1189,10 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD, return RValue::get(Dest.getPointer()); } + case Builtin::BI__builtin_char_memchr: + BuiltinID = Builtin::BI__builtin_memchr; + break; + case Builtin::BI__builtin___memcpy_chk: { // fold __builtin_memcpy_chk(x, y, cst1, cst2) to memcpy iff cst1<=cst2. llvm::APSInt Size, DstSize; diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp index aebebaac46..de166c75e2 100644 --- a/lib/Lex/PPMacroExpansion.cpp +++ b/lib/Lex/PPMacroExpansion.cpp @@ -1183,6 +1183,7 @@ static bool HasFeature(const Preprocessor &PP, StringRef Feature) { .Case("cxx_attributes", LangOpts.CPlusPlus11) .Case("cxx_auto_type", LangOpts.CPlusPlus11) .Case("cxx_constexpr", LangOpts.CPlusPlus11) + .Case("cxx_constexpr_string_builtins", LangOpts.CPlusPlus11) .Case("cxx_decltype", LangOpts.CPlusPlus11) .Case("cxx_decltype_incomplete_return_types", LangOpts.CPlusPlus11) .Case("cxx_default_function_template_args", LangOpts.CPlusPlus11) diff --git a/test/CodeGenCXX/builtins.cpp b/test/CodeGenCXX/builtins.cpp index 98e2d1a827..a49deea252 100644 --- a/test/CodeGenCXX/builtins.cpp +++ b/test/CodeGenCXX/builtins.cpp @@ -26,3 +26,7 @@ int x = __builtin_abs(-2); long y = __builtin_abs(-2l); // CHECK: [[Y:%.+]] = call i64 @_Z13__builtin_absl(i64 -2) // CHECK: store i64 [[Y]], i64* @y, align 8 + +extern const char char_memchr_arg[32]; +char *memchr_result = __builtin_char_memchr(char_memchr_arg, 123, 32); +// CHECK: call i8* @memchr(i8* getelementptr inbounds ([32 x i8], [32 x i8]* @char_memchr_arg, i32 0, i32 0), i32 123, i64 32) diff --git a/test/Lexer/has_feature_cxx0x.cpp b/test/Lexer/has_feature_cxx0x.cpp index 8c7ff18860..9082ca848c 100644 --- a/test/Lexer/has_feature_cxx0x.cpp +++ b/test/Lexer/has_feature_cxx0x.cpp @@ -301,6 +301,17 @@ int no_constexpr(); // CHECK-11: has_constexpr // CHECK-NO-11: no_constexpr +#if __has_feature(cxx_constexpr_string_builtins) +int has_constexpr_string_builtins(); +#else +int no_constexpr_string_builtins(); +#endif + +// CHECK-1Z: has_constexpr_string_builtins +// CHECK-14: has_constexpr_string_builtins +// CHECK-11: has_constexpr_string_builtins +// CHECK-NO-11: no_constexpr_string_builtins + #if __has_feature(cxx_generalized_initializers) int has_generalized_initializers(); #else diff --git a/test/SemaCXX/constexpr-string.cpp b/test/SemaCXX/constexpr-string.cpp index 944038bc16..fba05e508a 100644 --- a/test/SemaCXX/constexpr-string.cpp +++ b/test/SemaCXX/constexpr-string.cpp @@ -166,6 +166,27 @@ namespace StrchrEtc { static_assert(__builtin_memchr(nullptr, 'x', 3) == nullptr); // expected-error {{not an integral constant}} expected-note {{dereferenced null}} static_assert(__builtin_memchr(nullptr, 'x', 0) == nullptr); // FIXME: Should we reject this? + static_assert(__builtin_char_memchr(kStr, 'a', 0) == nullptr); + static_assert(__builtin_char_memchr(kStr, 'a', 1) == kStr); + static_assert(__builtin_char_memchr(kStr, '\0', 5) == nullptr); + static_assert(__builtin_char_memchr(kStr, '\0', 6) == kStr + 5); + static_assert(__builtin_char_memchr(kStr, '\xff', 8) == kStr + 4); + static_assert(__builtin_char_memchr(kStr, '\xff' + 256, 8) == kStr + 4); + static_assert(__builtin_char_memchr(kStr, '\xff' - 256, 8) == kStr + 4); + static_assert(__builtin_char_memchr(kFoo, 'x', 3) == nullptr); + static_assert(__builtin_char_memchr(kFoo, 'x', 4) == nullptr); // expected-error {{not an integral constant}} expected-note {{dereferenced one-past-the-end}} + static_assert(__builtin_char_memchr(nullptr, 'x', 3) == nullptr); // expected-error {{not an integral constant}} expected-note {{dereferenced null}} + static_assert(__builtin_char_memchr(nullptr, 'x', 0) == nullptr); // FIXME: Should we reject this? + + static_assert(*__builtin_char_memchr(kStr, '\xff', 8) == '\xff'); + constexpr bool char_memchr_mutable() { + char buffer[] = "mutable"; + *__builtin_char_memchr(buffer, 't', 8) = 'r'; + *__builtin_char_memchr(buffer, 'm', 8) = 'd'; + return __builtin_strcmp(buffer, "durable") == 0; + } + static_assert(char_memchr_mutable()); + constexpr bool a = !strchr("hello", 'h'); // expected-error {{constant expression}} expected-note {{non-constexpr function 'strchr' cannot be used in a constant expression}} constexpr bool b = !memchr("hello", 'h', 3); // expected-error {{constant expression}} expected-note {{non-constexpr function 'memchr' cannot be used in a constant expression}} } -- cgit v1.2.3