Changes in directory llvm/lib/Transforms/Scalar:
InstructionCombining.cpp updated: 1.740 -> 1.741
---
Log message:
Simplify some comparisons to arithmetic, this implements:
Transforms/InstCombine/icmp.ll
---
Diffs of the changes: (+27 -0)
InstructionCombining.cpp | 27 +++++++++++++++++++++++++++
1 files changed, 27 insertions(+)
Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp
diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.740
llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.741
--- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.740 Wed Apr 11
01:12:58 2007
+++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp Wed Apr 11 01:53:04 2007
@@ -6570,6 +6570,33 @@
// cast to integer to avoid the comparison.
if (ConstantInt *Op1C = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
const APInt &Op1CV = Op1C->getValue();
+
+ // zext (x <s 0) to i32 --> x>>u31 true if signbit set.
+ // zext (x >s -1) to i32 --> (x>>u31)^1 true if signbit clear.
+ if ((ICI->getPredicate() == ICmpInst::ICMP_SLT && Op1CV == 0) ||
+ (ICI->getPredicate() == ICmpInst::ICMP_SGT
&&Op1CV.isAllOnesValue())){
+ Value *In = ICI->getOperand(0);
+ Value *Sh = ConstantInt::get(In->getType(),
+ In->getType()->getPrimitiveSizeInBits()-1);
+ In = InsertNewInstBefore(BinaryOperator::createLShr(In, Sh,
+
In->getName()+".lobit"),
+ CI);
+ if (In->getType() != CI.getType())
+ In = CastInst::createIntegerCast(In, CI.getType(),
+ false/*ZExt*/, "tmp", &CI);
+
+ if (ICI->getPredicate() == ICmpInst::ICMP_SGT) {
+ Constant *One = ConstantInt::get(In->getType(), 1);
+ In = InsertNewInstBefore(BinaryOperator::createXor(In, One,
+
In->getName()+".not"),
+ CI);
+ }
+
+ return ReplaceInstUsesWith(CI, In);
+ }
+
+
+
// zext (X == 0) to i32 --> X^1 iff X has only the low bit set.
// zext (X == 0) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
// zext (X == 1) to i32 --> X iff X has only the low bit set.
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