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author | Rafael Espindola <rafael.espindola@gmail.com> | 2014-05-30 15:54:32 +0000 |
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committer | Rafael Espindola <rafael.espindola@gmail.com> | 2014-05-30 15:54:32 +0000 |
commit | fcb9926813ef9bd18bf2b3aab4ab58c6522c2c5e (patch) | |
tree | 6ad8e9a57ca6f0b0eefabe1b5e2a80d39a63e4c5 /lib/Transforms/InstCombine | |
parent | 6319c0c5203450e9d9a79cc6d57764b97d814da2 (diff) | |
download | llvm-fcb9926813ef9bd18bf2b3aab4ab58c6522c2c5e.tar.gz llvm-fcb9926813ef9bd18bf2b3aab4ab58c6522c2c5e.tar.bz2 llvm-fcb9926813ef9bd18bf2b3aab4ab58c6522c2c5e.tar.xz |
PR19753: Optimize comparisons with "ashr exact" of a constanst.
Patch by suyog sarda.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209903 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms/InstCombine')
-rw-r--r-- | lib/Transforms/InstCombine/InstCombineCompares.cpp | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp index 02e8bf1013..79cd1fba85 100644 --- a/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -2439,6 +2439,23 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) { return new ICmpInst(I.getPredicate(), A, B); } + // PR19753: + // (icmp (ashr exact const2, A), const1) -> icmp A, Log2(const2/const1) + // Cases where const1 doesn't divide const2 exactly or Quotient is not + // exact of log2 are handled by SimplifyICmpInst call above where we + // return false. + // TODO: Handle this for lshr exact with udiv. + { + ConstantInt *CI2; + if (match(Op0, m_AShr(m_ConstantInt(CI2), m_Value(A))) && + (cast<BinaryOperator>(Op0)->isExact())) { + APInt Quotient = CI2->getValue().sdiv(CI->getValue()); + unsigned shift = Quotient.logBase2(); + return new ICmpInst(I.getPredicate(), A, + ConstantInt::get(A->getType(), shift)); + } + } + // If we have an icmp le or icmp ge instruction, turn it into the // appropriate icmp lt or icmp gt instruction. This allows us to rely on // them being folded in the code below. The SimplifyICmpInst code has |