Disable the (A == (B-A)) -> 2*A == B xform when the sub has multiple uses (in
this case, the xform introduces an extra operation). This compiles
PowerPC/compare-duplicate.ll into:
_test:
subf r2, r3, r4
cmplw cr0, r2, r3
bne cr0, LBB1_2 ;F
instead of:
_test:
slwi r2, r3, 1
subf r3, r3, r4
cmplw cr0, r4, r2
bne cr0, LBB1_2 ;F
This is target independent of course.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37246 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index a2cd128..e5883f6 100644
--- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -1785,7 +1785,7 @@
if (DAG.isCommutativeBinOp(N0.getOpcode()))
return DAG.getSetCC(VT, N0.getOperand(0),
DAG.getConstant(0, N0.getValueType()), Cond);
- else {
+ else if (N0.Val->hasOneUse()) {
assert(N0.getOpcode() == ISD::SUB && "Unexpected operation!");
// (Z-X) == X --> Z == X<<1
SDOperand SH = DAG.getNode(ISD::SHL, N1.getValueType(),