From a958cbfe367ed7bf6a3a260b28a7b19cf70b7d9f Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Mon, 11 Jan 2010 22:45:25 +0000 Subject: Disable folding sext(trunc(x)) -> x (and other similar cast/cast cases) when the trunc has multiple uses. Codegen is not able to coalesce the subreg case correctly and so this leads to higher register pressure and spilling (see PR5997). This speeds up 256.bzip2 from 8.60 -> 8.04s on my machine, ~7%. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93200 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/InstCombine/InstCombineCasts.cpp | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp index 939c2b1..b5da3e6 100644 --- a/lib/Transforms/InstCombine/InstCombineCasts.cpp +++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp @@ -325,8 +325,11 @@ static bool CanEvaluateTruncated(Value *V, const Type *Ty) { const Type *OrigTy = V->getType(); - // If this is an extension from the dest type, we can eliminate it. - if ((isa(I) || isa(I)) && + // If this is an extension from the dest type, we can eliminate it, even if it + // has multiple uses. + // FIXME: This is currently disabled until codegen can handle this without + // pessimizing code, PR5997. + if (0 && (isa(I) || isa(I)) && I->getOperand(0)->getType() == Ty) return true; @@ -606,8 +609,10 @@ static bool CanEvaluateZExtd(Value *V, const Type *Ty, unsigned &BitsToClear) { if (!I) return false; // If the input is a truncate from the destination type, we can trivially - // eliminate it. - if (isa(I) && I->getOperand(0)->getType() == Ty) + // eliminate it, even if it has multiple uses. + // FIXME: This is currently disabled until codegen can handle this without + // pessimizing code, PR5997. + if (0 && isa(I) && I->getOperand(0)->getType() == Ty) return true; // We can't extend or shrink something that has multiple uses: doing so would @@ -853,8 +858,11 @@ static bool CanEvaluateSExtd(Value *V, const Type *Ty) { Instruction *I = dyn_cast(V); if (!I) return false; - // If this is a truncate from the dest type, we can trivially eliminate it. - if (isa(I) && I->getOperand(0)->getType() == Ty) + // If this is a truncate from the dest type, we can trivially eliminate it, + // even if it has multiple uses. + // FIXME: This is currently disabled until codegen can handle this without + // pessimizing code, PR5997. + if (0 && isa(I) && I->getOperand(0)->getType() == Ty) return true; // We can't extend or shrink something that has multiple uses: doing so would -- cgit v1.1