Thread comparisons over udiv/sdiv/ashr/lshr exact and lshr nuw/nsw whenever
possible. This goes into instcombine and instsimplify because instsimplify
doesn't need to check hasOneUse since it returns (almost exclusively) constants.
This fixes PR9343 #4 #5 and #8!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127064 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 239cd23..bdef3db 100644
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2393,6 +2393,27 @@
}
}
break;
+ case Instruction::UDiv:
+ case Instruction::LShr:
+ if (I.isSigned())
+ break;
+ // fall-through
+ case Instruction::SDiv:
+ case Instruction::AShr:
+ if (!BO0->isExact() && !BO1->isExact())
+ break;
+ return new ICmpInst(I.getPredicate(), BO0->getOperand(0),
+ BO1->getOperand(0));
+ case Instruction::Shl: {
+ bool NUW = BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap();
+ bool NSW = BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap();
+ if (!NUW && !NSW)
+ break;
+ if (!NSW && I.isSigned())
+ break;
+ return new ICmpInst(I.getPredicate(), BO0->getOperand(0),
+ BO1->getOperand(0));
+ }
}
}
}