Author: majnemer Date: Thu Oct 27 12:18:24 2016 New Revision: 285316 URL: http://llvm.org/viewvc/llvm-project?rev=285316&view=rev Log: [CodeGen] Provide an appropriate alignment for dynamic allocas
GCC documents __builtin_alloca as aligning the storage to at least __BIGGEST_ALIGNMENT__. MSVC documents essentially the same for the x64 ABI: https://msdn.microsoft.com/en-us/library/x9sx5da1.aspx The 32-bit ABI follows the same rule: it emits a call to _alloca_probe_16 Differential Revision: https://reviews.llvm.org/D24378 Modified: cfe/trunk/lib/CodeGen/CGBuiltin.cpp cfe/trunk/test/CodeGen/builtins-ms.c Modified: cfe/trunk/lib/CodeGen/CGBuiltin.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGBuiltin.cpp?rev=285316&r1=285315&r2=285316&view=diff ============================================================================== --- cfe/trunk/lib/CodeGen/CGBuiltin.cpp (original) +++ cfe/trunk/lib/CodeGen/CGBuiltin.cpp Thu Oct 27 12:18:24 2016 @@ -1139,7 +1139,13 @@ RValue CodeGenFunction::EmitBuiltinExpr( case Builtin::BI_alloca: case Builtin::BI__builtin_alloca: { Value *Size = EmitScalarExpr(E->getArg(0)); - return RValue::get(Builder.CreateAlloca(Builder.getInt8Ty(), Size)); + const TargetInfo &TI = getContext().getTargetInfo(); + // The alignment of the alloca should correspond to __BIGGEST_ALIGNMENT__. + unsigned SuitableAlignmentInBytes = + TI.getSuitableAlign() / TI.getCharWidth(); + AllocaInst *AI = Builder.CreateAlloca(Builder.getInt8Ty(), Size); + AI->setAlignment(SuitableAlignmentInBytes); + return RValue::get(AI); } case Builtin::BIbzero: case Builtin::BI__builtin_bzero: { Modified: cfe/trunk/test/CodeGen/builtins-ms.c URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/builtins-ms.c?rev=285316&r1=285315&r2=285316&view=diff ============================================================================== --- cfe/trunk/test/CodeGen/builtins-ms.c (original) +++ cfe/trunk/test/CodeGen/builtins-ms.c Thu Oct 27 12:18:24 2016 @@ -4,6 +4,6 @@ void capture(void *); void test_alloca(int n) { capture(_alloca(n)); - // CHECK: %[[arg:.*]] = alloca i8, i32 % + // CHECK: %[[arg:.*]] = alloca i8, i32 %{{.*}}, align 16 // CHECK: call void @capture(i8* %[[arg]]) } _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
