[llvm] r289888 - [SimplifyLibCalls] Remove redundant folding logic for ffs().
Davide Italiano via llvm-commits
llvm-commits at lists.llvm.org
Thu Dec 15 15:11:00 PST 2016
Author: davide
Date: Thu Dec 15 17:11:00 2016
New Revision: 289888
URL: http://llvm.org/viewvc/llvm-project?rev=289888&view=rev
Log:
[SimplifyLibCalls] Remove redundant folding logic for ffs().
Lowering to llvm.cttz() will result in constant folding anyway
if the argument to ffs is a constant. Pointed out by Eli for
fls() in D14590.
Modified:
llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp?rev=289888&r1=289887&r2=289888&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp Thu Dec 15 17:11:00 2016
@@ -1521,21 +1521,11 @@ void LibCallSimplifier::replaceTrigInsts
//===----------------------------------------------------------------------===//
Value *LibCallSimplifier::optimizeFFS(CallInst *CI, IRBuilder<> &B) {
- Function *Callee = CI->getCalledFunction();
- Value *Op = CI->getArgOperand(0);
-
- // Constant fold.
- if (ConstantInt *CI = dyn_cast<ConstantInt>(Op)) {
- if (CI->isZero()) // ffs(0) -> 0.
- return B.getInt32(0);
- // ffs(c) -> cttz(c)+1
- return B.getInt32(CI->getValue().countTrailingZeros() + 1);
- }
-
// ffs(x) -> x != 0 ? (i32)llvm.cttz(x)+1 : 0
+ Value *Op = CI->getArgOperand(0);
Type *ArgType = Op->getType();
- Value *F =
- Intrinsic::getDeclaration(Callee->getParent(), Intrinsic::cttz, ArgType);
+ Value *F = Intrinsic::getDeclaration(CI->getCalledFunction()->getParent(),
+ Intrinsic::cttz, ArgType);
Value *V = B.CreateCall(F, {Op, B.getTrue()}, "cttz");
V = B.CreateAdd(V, ConstantInt::get(V->getType(), 1));
V = B.CreateIntCast(V, B.getInt32Ty(), false);
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