Author: resistor
Date: Fri Dec 28 01:42:12 2007
New Revision: 45384
URL: http://llvm.org/viewvc/llvm-project?rev=45384&view=rev
Log:
Repair a transform that Chris noticed a bug in. Thanks to Nicholas for
pointing out my stupid mistakes when writing this patch. :-)
Modified:
llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=45384&r1=45383&r2=45384&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Fri Dec 28
01:42:12 2007
@@ -4835,11 +4835,18 @@
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
Value *A, *B;
-#if 0
- // (icmp cond (sub A B) 0) -> (icmp cond A B)
- if (CI->isNullValue() && match(Op0, m_Sub(m_Value(A), m_Value(B))))
- return new ICmpInst(I.getPredicate(), A, B);
-#endif
+ // (icmp cond (sub A B) 0) -> ...
+ if (CI->isNullValue() && match(Op0, m_Sub(m_Value(A), m_Value(B)))) {
+ // (icmp cond A B) if cond is signed or equality
+ if (CmpInst::isSigned(I.getPredicate()) || I.isEquality())
+ return new ICmpInst(I.getPredicate(), A, B);
+ // (icmp ne A B) if cond is ugt
+ else if (I.getPredicate() == ICmpInst::ICMP_UGT)
+ return new ICmpInst(ICmpInst::ICMP_NE, A, B);
+ // (icmp eq A B) if cond is ule
+ else if (I.getPredicate() == ICmpInst::ICMP_ULE)
+ return new ICmpInst(ICmpInst::ICMP_EQ, A, B);
+ }
switch (I.getPredicate()) {
default: break;
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