Changes in directory llvm/lib/Transforms/Scalar:
InstructionCombining.cpp updated: 1.741 -> 1.742
---
Log message:
Turn stuff like:
icmp slt i32 %X, 0 ; <i1>:0 [#uses=1]
sext i1 %0 to i32 ; <i32>:1 [#uses=1]
into:
%X.lobit = ashr i32 %X, 31 ; <i32> [#uses=1]
This implements InstCombine/icmp.ll:test[34]
---
Diffs of the changes: (+40 -9)
InstructionCombining.cpp | 49 ++++++++++++++++++++++++++++++++++++++---------
1 files changed, 40 insertions(+), 9 deletions(-)
Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp
diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.741
llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.742
--- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.741 Wed Apr 11
01:53:04 2007
+++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp Wed Apr 11 01:57:46 2007
@@ -193,9 +193,9 @@
BinaryOperator &I);
Instruction *commonCastTransforms(CastInst &CI);
Instruction *commonIntCastTransforms(CastInst &CI);
- Instruction *visitTrunc(CastInst &CI);
- Instruction *visitZExt(CastInst &CI);
- Instruction *visitSExt(CastInst &CI);
+ Instruction *visitTrunc(TruncInst &CI);
+ Instruction *visitZExt(ZExtInst &CI);
+ Instruction *visitSExt(SExtInst &CI);
Instruction *visitFPTrunc(CastInst &CI);
Instruction *visitFPExt(CastInst &CI);
Instruction *visitFPToUI(CastInst &CI);
@@ -6471,7 +6471,7 @@
return 0;
}
-Instruction *InstCombiner::visitTrunc(CastInst &CI) {
+Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
if (Instruction *Result = commonIntCastTransforms(CI))
return Result;
@@ -6528,7 +6528,7 @@
return 0;
}
-Instruction *InstCombiner::visitZExt(CastInst &CI) {
+Instruction *InstCombiner::visitZExt(ZExtInst &CI) {
// If one of the common conversion will work ..
if (Instruction *Result = commonIntCastTransforms(CI))
return Result;
@@ -6653,13 +6653,44 @@
return 0;
}
-Instruction *InstCombiner::visitSExt(CastInst &CI) {
+Instruction *InstCombiner::visitSExt(SExtInst &CI) {
if (Instruction *I = commonIntCastTransforms(CI))
return I;
- // (x <s 0) ? -1 : 0 -> ashr x, 31
- // (x >u 2147483647) ? -1 : 0 -> ashr x, 31
-
+ Value *Src = CI.getOperand(0);
+
+ // sext (x <s 0) -> ashr x, 31 -> all ones if signed
+ // sext (x >s -1) -> ashr x, 31 -> all ones if not signed
+ if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src)) {
+ // If we are just checking for a icmp eq of a single bit and zext'ing it
+ // to an integer, then shift the bit to the appropriate place and then
+ // cast to integer to avoid the comparison.
+ if (ConstantInt *Op1C = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
+ const APInt &Op1CV = Op1C->getValue();
+
+ // sext (x <s 0) to i32 --> x>>s31 true if signbit set.
+ // sext (x >s -1) to i32 --> (x>>s31)^-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::createAShr(In, Sh,
+
In->getName()+".lobit"),
+ CI);
+ if (In->getType() != CI.getType())
+ In = CastInst::createIntegerCast(In, CI.getType(),
+ true/*SExt*/, "tmp", &CI);
+
+ if (ICI->getPredicate() == ICmpInst::ICMP_SGT)
+ In = InsertNewInstBefore(BinaryOperator::createNot(In,
+ In->getName()+".not"), CI);
+
+ return ReplaceInstUsesWith(CI, In);
+ }
+ }
+ }
+
return 0;
}
_______________________________________________
llvm-commits mailing list
llvm-commits@cs.uiuc.edu
http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
