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[msan] Transform memcpy and memset to library calls.

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This was already done for memmove, where it is required for correctness.
This change improves performance by avoiding copyingthe same memory twice.
Also, the library functions are given __msan_ prefix to prevent instcombine
pass from converting them back to intrinsics.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168876 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evgeniy Stepanov 2012-11-29 12:49:04 +00:00
parent 8564dc67b5
commit 2e815e7cf4
1 changed files with 35 additions and 34 deletions
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69
lib/Transforms/Instrumentation/MemorySanitizer.cpp
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@ -170,8 +170,8 @@ private:
Value *MsanSetAllocaOriginFn;
/// \brief Run-time helper that poisons stack on function entry.
Value *MsanPoisonStackFn;
/// \brief The actual "memmove" function.
Value *MemmoveFn;
/// \brief MSan runtime replacements for memmove, memcpy and memset.
Value *MemmoveFn, *MemcpyFn, *MemsetFn;
/// \brief Address mask used in application-to-shadow address calculation.
/// ShadowAddr is computed as ApplicationAddr & ~ShadowMask.
@ -266,7 +266,13 @@ bool MemorySanitizer::doInitialization(Module &M) {
MsanPoisonStackFn = M.getOrInsertFunction(
"__msan_poison_stack", IRB.getVoidTy(), IRB.getInt8PtrTy(), IntptrTy, NULL);
MemmoveFn = M.getOrInsertFunction(
"memmove", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
"__msan_memmove", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
IntptrTy, NULL);
MemcpyFn = M.getOrInsertFunction(
"__msan_memcpy", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
IntptrTy, NULL);
MemsetFn = M.getOrInsertFunction(
"__msan_memset", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IRB.getInt32Ty(),
IntptrTy, NULL);
// Create globals.
@ -969,35 +975,6 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
void visitAShr(BinaryOperator &I) { handleShift(I); }
void visitLShr(BinaryOperator &I) { handleShift(I); }
void visitMemSetInst(MemSetInst &I) {
IRBuilder<> IRB(&I);
Value *Ptr = I.getArgOperand(0);
Value *Val = I.getArgOperand(1);
Value *ShadowPtr = getShadowPtr(Ptr, Val->getType(), IRB);
Value *ShadowVal = getCleanShadow(Val);
Value *Size = I.getArgOperand(2);
unsigned Align = I.getAlignment();
bool isVolatile = I.isVolatile();
IRB.CreateMemSet(ShadowPtr, ShadowVal, Size, Align, isVolatile);
}
void visitMemCpyInst(MemCpyInst &I) {
IRBuilder<> IRB(&I);
Value *Dst = I.getArgOperand(0);
Value *Src = I.getArgOperand(1);
Type *ElementType = dyn_cast<PointerType>(Dst->getType())->getElementType();
Value *ShadowDst = getShadowPtr(Dst, ElementType, IRB);
Value *ShadowSrc = getShadowPtr(Src, ElementType, IRB);
Value *Size = I.getArgOperand(2);
unsigned Align = I.getAlignment();
bool isVolatile = I.isVolatile();
IRB.CreateMemCpy(ShadowDst, ShadowSrc, Size, Align, isVolatile);
if (ClTrackOrigins)
IRB.CreateCall3(MS.MsanCopyOriginFn, Dst, Src, Size);
}
/// \brief Instrument llvm.memmove
///
/// At this point we don't know if llvm.memmove will be inlined or not.
@ -1007,8 +984,7 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
/// we will memove the shadow twice: which is bad in case
/// of overlapping regions. So, we simply lower the intrinsic to a call.
///
/// Similar situation exists for memcpy and memset, but for those functions
/// calling instrumentation twice does not lead to incorrect results.
/// Similar situation exists for memcpy and memset.
void visitMemMoveInst(MemMoveInst &I) {
IRBuilder<> IRB(&I);
IRB.CreateCall3(
@ -1019,6 +995,31 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
I.eraseFromParent();
}
// Similar to memmove: avoid copying shadow twice.
// This is somewhat unfortunate as it may slowdown small constant memcpys.
// FIXME: consider doing manual inline for small constant sizes and proper
// alignment.
void visitMemCpyInst(MemCpyInst &I) {
IRBuilder<> IRB(&I);
IRB.CreateCall3(
MS.MemcpyFn,
IRB.CreatePointerCast(I.getArgOperand(0), IRB.getInt8PtrTy()),
IRB.CreatePointerCast(I.getArgOperand(1), IRB.getInt8PtrTy()),
IRB.CreateIntCast(I.getArgOperand(2), MS.IntptrTy, false));
I.eraseFromParent();
}
// Same as memcpy.
void visitMemSetInst(MemSetInst &I) {
IRBuilder<> IRB(&I);
IRB.CreateCall3(
MS.MemsetFn,
IRB.CreatePointerCast(I.getArgOperand(0), IRB.getInt8PtrTy()),
IRB.CreateIntCast(I.getArgOperand(1), IRB.getInt32Ty(), false),
IRB.CreateIntCast(I.getArgOperand(2), MS.IntptrTy, false));
I.eraseFromParent();
}
void visitVAStartInst(VAStartInst &I) {
VAHelper->visitVAStartInst(I);
}