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[msan] Avoid redundant origin stores.

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Origin is meaningless for fully initialized values. Avoid
storing origin for function arguments that are known to
be always initialized (i.e. shadow is a compile-time null
constant).

This is not about correctness, but purely an optimization.
Seems to affect compilation time of blacklisted functions
significantly.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213239 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evgeniy Stepanov 2014-07-17 09:10:37 +00:00
parent c84f22aac5
commit e1287f556f
2 changed files with 22 additions and 1 deletions
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5
lib/Transforms/Instrumentation/MemorySanitizer.cpp
View File

@ -2313,6 +2313,7 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
Value *ArgShadowBase = getShadowPtrForArgument(A, IRB, ArgOffset);
DEBUG(dbgs() << " Arg#" << i << ": " << *A <<
" Shadow: " << *ArgShadow << "\n");
bool ArgIsInitialized = false;
if (CS.paramHasAttr(i + 1, Attribute::ByVal)) {
assert(A->getType()->isPointerTy() &&
"ByVal argument is not a pointer!");
@ -2325,8 +2326,10 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
Size = MS.DL->getTypeAllocSize(A->getType());
Store = IRB.CreateAlignedStore(ArgShadow, ArgShadowBase,
kShadowTLSAlignment);
Constant *Cst = dyn_cast<Constant>(ArgShadow);
if (Cst && Cst->isNullValue()) ArgIsInitialized = true;
}
if (MS.TrackOrigins)
if (MS.TrackOrigins && !ArgIsInitialized)
IRB.CreateStore(getOrigin(A),
getOriginPtrForArgument(A, IRB, ArgOffset));
(void)Store;

18
test/Instrumentation/MemorySanitizer/msan_basic.ll
View File

@ -766,6 +766,24 @@ cond.end: ; preds = %cond.false, %cond.t
; CHECK: ret i32 [[A]]
; Test that there are no __msan_param_origin_tls stores when
; argument shadow is a compile-time zero constant (which is always the case
; in functions missing sanitize_memory attribute).
define i32 @NoSanitizeMemoryParamTLS(i32* nocapture readonly %x) {
entry:
%0 = load i32* %x, align 4
%call = tail call i32 @NoSanitizeMemoryParamTLSHelper(i32 %0)
ret i32 %call
}
declare i32 @NoSanitizeMemoryParamTLSHelper(i32 %x)
; CHECK-LABEL: define i32 @NoSanitizeMemoryParamTLS(
; CHECK-NOT: __msan_param_origin_tls
; CHECK: ret i32
; Test argument shadow alignment
define <2 x i64> @ArgumentShadowAlignment(i64 %a, <2 x i64> %b) sanitize_memory {