fix a small oversight in the "eliminate memcpy from constant global"
optimization. If the alloca that is "memcpy'd from constant" also has
a memcpy from *it*, ignore it: it is a load. We now optimize the testcase to:
define void @test2() {
%B = alloca %T
%a = bitcast %T* @G to i8*
%b = bitcast %T* %B to i8*
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %b, i8* %a, i64 124, i32 4, i1 false)
call void @bar(i8* %b)
ret void
}
previously we would generate:
define void @test() {
%B = alloca %T
%b = bitcast %T* %B to i8*
%G.0 = getelementptr inbounds %T* @G, i32 0, i32 0
%tmp3 = load i8* %G.0, align 4
%G.1 = getelementptr inbounds %T* @G, i32 0, i32 1
%G.15 = bitcast [123 x i8]* %G.1 to i8*
%1 = bitcast [123 x i8]* %G.1 to i984*
%srcval = load i984* %1, align 1
%B.0 = getelementptr inbounds %T* %B, i32 0, i32 0
store i8 %tmp3, i8* %B.0, align 4
%B.1 = getelementptr inbounds %T* %B, i32 0, i32 1
%B.12 = bitcast [123 x i8]* %B.1 to i8*
%2 = bitcast [123 x i8]* %B.1 to i984*
store i984 %srcval, i984* %2, align 1
call void @bar(i8* %b)
ret void
}
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119682 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/ScalarReplAggregates.cpp b/lib/Transforms/Scalar/ScalarReplAggregates.cpp
index 8b4f355..6f4f17e 100644
--- a/lib/Transforms/Scalar/ScalarReplAggregates.cpp
+++ b/lib/Transforms/Scalar/ScalarReplAggregates.cpp
@@ -1789,10 +1789,11 @@
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
User *U = cast<Instruction>(*UI);
- if (LoadInst *LI = dyn_cast<LoadInst>(U))
+ if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
// Ignore non-volatile loads, they are always ok.
- if (!LI->isVolatile())
- continue;
+ if (LI->isVolatile()) return false;
+ continue;
+ }
if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
// If uses of the bitcast are ok, we are ok.
@@ -1814,6 +1815,13 @@
MemTransferInst *MI = dyn_cast<MemTransferInst>(U);
if (MI == 0)
return false;
+
+ // If the transfer is using the alloca as a source of the transfer, then
+ // it (unless the transfer is volatile).
+ if (UI.getOperandNo() == 1) {
+ if (MI->isVolatile()) return false;
+ continue;
+ }
// If we already have seen a copy, reject the second one.
if (TheCopy) return false;