diff options
Diffstat (limited to 'clang/lib/CodeGen/CGExprAgg.cpp')
| -rw-r--r-- | clang/lib/CodeGen/CGExprAgg.cpp | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/clang/lib/CodeGen/CGExprAgg.cpp b/clang/lib/CodeGen/CGExprAgg.cpp index e2f5c79d994..b0596e2feeb 100644 --- a/clang/lib/CodeGen/CGExprAgg.cpp +++ b/clang/lib/CodeGen/CGExprAgg.cpp @@ -518,7 +518,16 @@ void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr, llvm::Value *SrcPtr, QualType Ty) { assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex"); - // Aggregate assignment turns into llvm.memmove. + // Aggregate assignment turns into llvm.memset. This is almost valid per + // C99 6.5.16.1p3, which states "If the value being stored in an object is + // read from another object that overlaps in anyway the storage of the first + // object, then the overlap shall be exact and the two objects shall have + // qualified or unqualified versions of a compatible type." + // + // memset is not defined if the source and destination pointers are exactly + // equal, but other compilers do this optimization, and almost every memcpy + // implementation handles this case safely. If there is a libc that does not + // safely handle this, we can add a target hook. const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty); if (DestPtr->getType() != BP) DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp"); @@ -531,7 +540,7 @@ void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr, // FIXME: Handle variable sized types. const llvm::Type *IntPtr = llvm::IntegerType::get(LLVMPointerWidth); - Builder.CreateCall4(CGM.getMemMoveFn(), + Builder.CreateCall4(CGM.getMemCpyFn(), DestPtr, SrcPtr, // TypeInfo.first describes size in bits. llvm::ConstantInt::get(IntPtr, TypeInfo.first/8), |
