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enhance memcpyopt to zap memcpy's that have the same src/dst.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121362 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-12-09 07:45:45 +00:00
parent f7f35467a9
commit 8fdca6a873
2 changed files with 22 additions and 4 deletions
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17
lib/Transforms/Scalar/MemCpyOptimizer.cpp
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@ -762,6 +762,14 @@ bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
ConstantInt *CopySize = dyn_cast<ConstantInt>(M->getLength());
if (CopySize == 0 || M->isVolatile()) return false;
// If the source and destination of the memcpy are the same, then zap it.
if (M->getSource() == M->getDest()) {
MD->removeInstruction(M);
M->eraseFromParent();
return false;
}
// The are two possible optimizations we can do for memcpy:
// a) memcpy-memcpy xform which exposes redundance for DSE.
// b) call-memcpy xform for return slot optimization.
@ -773,10 +781,11 @@ bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
return processMemCpyMemCpyDependence(M, MDep, CopySize->getZExtValue());
if (CallInst *C = dyn_cast<CallInst>(DepInfo.getInst())) {
bool changed = performCallSlotOptzn(M, M->getDest(), M->getSource(),
CopySize->getZExtValue(), C);
if (changed) M->eraseFromParent();
return changed;
if (performCallSlotOptzn(M, M->getDest(), M->getSource(),
CopySize->getZExtValue(), C)) {
M->eraseFromParent();
return true;
}
}
return false;
}

9
test/Transforms/MemCpyOpt/memcpy.ll
View File

@ -100,3 +100,12 @@ entry:
; CHECK: store i8 4
; CHECK: call void @test5a(%struct.S* byval align 16 %y)
}
;; Noop memcpy should be zapped.
define void @test6(i8 *%P) {
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %P, i64 8, i32 4, i1 false)
ret void
; CHECK: @test6
; CHECK-NEXT: ret void
}