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| author | Arnaud A. de Grandmaison <arnaud.adegm@gmail.com> | 2013-03-13 14:40:37 +0000 |
|---|---|---|
| committer | Arnaud A. de Grandmaison <arnaud.adegm@gmail.com> | 2013-03-13 14:40:37 +0000 |
| commit | bdd2d981391bd9329aba669cffcdde0c39373cb1 (patch) | |
| tree | 4a5bacfb18f1a64079a083de39088c98232b6986 | |
| parent | dec29b61a49da09e8ed494dcc1466f160614f80d (diff) | |
Fix a performance regression when combining to smaller types in icmp (shl %v, C1), C2 :
Only combine when the shl is only used by the icmp
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176950 91177308-0d34-0410-b5e6-96231b3b80d8
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineCompares.cpp | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp index bad46b4dab..32fdb9b708 100644 --- a/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -1333,13 +1333,14 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI, } // Transform (icmp pred iM (shl iM %v, N), CI) - // -> (icmp pred i(M-N) (trunc %v iM to i(N-N)), (trunc (CI>>N)) - // Transform the shl to a trunc if (trunc (CI>>N)) has no loss. + // -> (icmp pred i(M-N) (trunc %v iM to i(M-N)), (trunc (CI>>N)) + // Transform the shl to a trunc if (trunc (CI>>N)) has no loss and M-N. // This enables to get rid of the shift in favor of a trunc which can be // free on the target. It has the additional benefit of comparing to a // smaller constant, which will be target friendly. unsigned Amt = ShAmt->getLimitedValue(TypeBits-1); - if (Amt != 0 && RHSV.countTrailingZeros() >= Amt) { + if (LHSI->hasOneUse() && + Amt != 0 && RHSV.countTrailingZeros() >= Amt) { Type *NTy = IntegerType::get(ICI.getContext(), TypeBits - Amt); Constant *NCI = ConstantExpr::getTrunc( ConstantExpr::getAShr(RHS, |