Merge memsets followed by neighboring memsets and other stores into
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
diff --git a/lib/Transforms/Scalar/MemCpyOptimizer.cpp b/lib/Transforms/Scalar/MemCpyOptimizer.cpp
index c284437..4210f0d 100644
--- a/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ b/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -322,6 +322,7 @@
// 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 @@
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 @@
return true;
}
}
+
return false;
}
@@ -884,11 +897,13 @@
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);