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Merge memsets followed by neighboring memsets and other stores into

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larger memsets.  Among other things, this fixes rdar://8760394 and
allows us to handle "Example 2" from http://blog.regehr.org/archives/320,
compiling it into a single 4096-byte memset:

_mad_synth_mute:                        ## @mad_synth_mute
## BB#0:                                ## %entry
	pushq	%rax
	movl	$4096, %esi             ## imm = 0x1000
	callq	___bzero
	popq	%rax
	ret



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123089 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2011-01-08 21:19:19 +00:00
parent 9fa11e94b5
commit d90a192279
2 changed files with 46 additions and 3 deletions
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21
lib/Transforms/Scalar/MemCpyOptimizer.cpp
View File

@ -322,6 +322,7 @@ namespace {
// Helper fuctions
bool processStore(StoreInst *SI, BasicBlock::iterator &BBI);
bool processMemSet(MemSetInst *SI, BasicBlock::iterator &BBI);
bool processMemCpy(MemCpyInst *M);
bool processMemMove(MemMoveInst *M);
bool performCallSlotOptzn(Instruction *cpy, Value *cpyDst, Value *cpySrc,
@ -511,6 +512,17 @@ bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
return false;
}
bool MemCpyOpt::processMemSet(MemSetInst *MSI, BasicBlock::iterator &BBI) {
// See if there is another memset or store neighboring this memset which
// allows us to widen out the memset to do a single larger store.
if (Instruction *I = tryMergingIntoMemset(MSI, MSI->getDest(),
MSI->getValue())) {
BBI = I; // Don't invalidate iterator.
return true;
}
return false;
}
/// performCallSlotOptzn - takes a memcpy and a call that it depends on,
/// and checks for the possibility of a call slot optimization by having
@ -775,6 +787,7 @@ bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
return true;
}
}
return false;
}
@ -884,11 +897,13 @@ bool MemCpyOpt::iterateOnFunction(Function &F) {
if (StoreInst *SI = dyn_cast<StoreInst>(I))
MadeChange |= processStore(SI, BI);
else if (MemCpyInst *M = dyn_cast<MemCpyInst>(I)) {
else if (MemSetInst *M = dyn_cast<MemSetInst>(I))
RepeatInstruction = processMemSet(M, BI);
else if (MemCpyInst *M = dyn_cast<MemCpyInst>(I))
RepeatInstruction = processMemCpy(M);
} else if (MemMoveInst *M = dyn_cast<MemMoveInst>(I)) {
else if (MemMoveInst *M = dyn_cast<MemMoveInst>(I))
RepeatInstruction = processMemMove(M);
} else if (CallSite CS = (Value*)I) {
else if (CallSite CS = (Value*)I) {
for (unsigned i = 0, e = CS.arg_size(); i != e; ++i)
if (CS.paramHasAttr(i+1, Attribute::ByVal))
MadeChange |= processByValArgument(CS, i);

28
test/Transforms/MemCpyOpt/form-memset.ll
View File

@ -164,6 +164,7 @@ entry:
declare void @foo(%struct.MV*, %struct.MV*, i8*)
; Store followed by memset.
define void @test3(i32* nocapture %P) nounwind ssp {
entry:
%arrayidx = getelementptr inbounds i32* %P, i64 1
@ -177,6 +178,7 @@ entry:
; CHECK: call void @llvm.memset.p0i8.i64(i8* %1, i8 0, i64 15, i32 4, i1 false)
}
; store followed by memset, different offset scenario
define void @test4(i32* nocapture %P) nounwind ssp {
entry:
store i32 0, i32* %P, align 4
@ -191,4 +193,30 @@ entry:
declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind
; Memset followed by store.
define void @test5(i32* nocapture %P) nounwind ssp {
entry:
%add.ptr = getelementptr inbounds i32* %P, i64 2
%0 = bitcast i32* %add.ptr to i8*
tail call void @llvm.memset.p0i8.i64(i8* %0, i8 0, i64 11, i32 1, i1 false)
%arrayidx = getelementptr inbounds i32* %P, i64 1
store i32 0, i32* %arrayidx, align 4
ret void
; CHECK: @test5
; CHECK-NOT: store
; CHECK: call void @llvm.memset.p0i8.i64(i8* %1, i8 0, i64 15, i32 4, i1 false)
}
;; Memset followed by memset.
define void @test6(i32* nocapture %P) nounwind ssp {
entry:
%0 = bitcast i32* %P to i8*
tail call void @llvm.memset.p0i8.i64(i8* %0, i8 0, i64 12, i32 1, i1 false)
%add.ptr = getelementptr inbounds i32* %P, i64 3
%1 = bitcast i32* %add.ptr to i8*
tail call void @llvm.memset.p0i8.i64(i8* %1, i8 0, i64 12, i32 1, i1 false)
ret void
; CHECK: @test6
; CHECK: call void @llvm.memset.p0i8.i64(i8* %2, i8 0, i64 24, i32 1, i1 false)
}