[llvm-commits] CVS: llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

[Chris Lattner]

Changes in directory llvm/lib/CodeGen/SelectionDAG:

TargetLowering.cpp updated: 1.116 -> 1.117
---
Log message:

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.



---
Diffs of the changes:  (+1 -1)

 TargetLowering.cpp |    2 +-
 1 files changed, 1 insertion(+), 1 deletion(-)


Index: llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
diff -u llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp:1.116 llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp:1.117
--- llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp:1.116	Fri May 18 12:52:13 2007
+++ llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp	Fri May 18 19:43:44 2007
@@ -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(),