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Fix PR26051: Memcpy optimization should introduce a call to memcpy before the store destination position

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This is a conservative fix, I expect Amaury to relax this.
Follow-up for r256923

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@256999 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Mehdi Amini 2016-01-06 23:50:22 +00:00
parent 3442ec90cd
commit 7fee368539
2 changed files with 18 additions and 2 deletions
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6
lib/Transforms/Scalar/MemCpyOptimizer.cpp
View File

@ -529,11 +529,13 @@ bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
// We found an instruction that may write to the loaded memory. // We found an instruction that may write to the loaded memory.
// We can try to promote at this position instead of the store // We can try to promote at this position instead of the store
// position if nothing alias the store memory after this. // position if nothing alias the store memory after this and the store
// destination is not in the range.
P = &*I; P = &*I;
for (; I != E; ++I) { for (; I != E; ++I) {
MemoryLocation StoreLoc = MemoryLocation::get(SI); MemoryLocation StoreLoc = MemoryLocation::get(SI);
if (AA.getModRefInfo(&*I, StoreLoc) != MRI_NoModRef) { if (&*I == SI->getOperand(1) ||
AA.getModRefInfo(&*I, StoreLoc) != MRI_NoModRef) {
P = nullptr; P = nullptr;
break; break;
} }

14
test/Transforms/MemCpyOpt/fca2memcpy.ll
View File

@ -72,3 +72,17 @@ define void @copyalias(%S* %src, %S* %dst) {
store %S %2, %S* %dst store %S %2, %S* %dst
ret void ret void
} }
; The GEP is present after the aliasing store, preventing to move the memcpy before
; (without further analysis/transformation)
define void @copyaliaswithproducerinbetween(%S* %src, %S* %dst) {
; CHECK-LABEL: copyalias
; CHECK-NEXT: [[LOAD:%[a-z0-9\.]+]] = load %S, %S* %src
; CHECK-NOT: call
%1 = load %S, %S* %src
store %S undef, %S* %dst
%dst2 = getelementptr %S , %S* %dst, i64 1
store %S %1, %S* %dst2
ret void
}