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author | Chris Lattner <sabre@nondot.org> | 2010-11-21 06:44:42 +0000 |
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committer | Chris Lattner <sabre@nondot.org> | 2010-11-21 06:44:42 +0000 |
commit | 75d8f599e72c151df48a28bebc6e4e342f469b8a (patch) | |
tree | 204abb357393b3d57e53da6a821c9780ded364f2 /lib/Transforms/InstCombine/InstCombineCompares.cpp | |
parent | 79a980ad85286614bbb4c68c84ea9e3c6ed36d0d (diff) | |
download | llvm-75d8f599e72c151df48a28bebc6e4e342f469b8a.tar.gz llvm-75d8f599e72c151df48a28bebc6e4e342f469b8a.tar.bz2 llvm-75d8f599e72c151df48a28bebc6e4e342f469b8a.tar.xz |
optimize:
void a(int x) { if (((1<<x)&8)==0) b(); }
into "x != 3", which occurs over 100 times in 403.gcc but in no
other program in llvm-test.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119922 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms/InstCombine/InstCombineCompares.cpp')
-rw-r--r-- | lib/Transforms/InstCombine/InstCombineCompares.cpp | 74 |
1 files changed, 72 insertions, 2 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp index d7e2b72b7f..8a35a5fcf3 100644 --- a/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -1744,14 +1744,84 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) { // simplify this comparison. For example, (x&4) < 8 is always true. switch (I.getPredicate()) { default: llvm_unreachable("Unknown icmp opcode!"); - case ICmpInst::ICMP_EQ: + case ICmpInst::ICMP_EQ: { if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max)) return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); + + // If all bits are known zero except for one, then we know at most one + // bit is set. If the comparison is against zero, then this is a check + // to see if *that* bit is set. + APInt Op0KnownZeroInverted = ~Op0KnownZero; + if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) { + // If the LHS is an AND with the same constant, look through it. + Value *LHS = 0; + ConstantInt *LHSC = 0; + if (!match(Op0, m_And(m_Value(LHS), m_ConstantInt(LHSC))) || + LHSC->getValue() != Op0KnownZeroInverted) + LHS = Op0; + + // If the LHS is 1 << x, and we know the result is a power of 2 like 8, + // then turn "((1 << x)&8) == 0" into "x == 3". + Value *X = 0; + if (match(LHS, m_Shl(m_One(), m_Value(X)))) { + unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros(); + return new ICmpInst(ICmpInst::ICMP_EQ, X, + ConstantInt::get(X->getType(), CmpVal)); + } + + // If the LHS is 8 >>u x, and we know the result is a power of 2 like 1, + // then turn "((8 >>u x)&1) == 0" into "x == 3". + ConstantInt *CI = 0; + if (Op0KnownZeroInverted == 1 && + match(LHS, m_LShr(m_ConstantInt(CI), m_Value(X))) && + CI->getValue().isPowerOf2()) { + unsigned CmpVal = CI->getValue().countTrailingZeros(); + return new ICmpInst(ICmpInst::ICMP_EQ, X, + ConstantInt::get(X->getType(), CmpVal)); + } + } + break; - case ICmpInst::ICMP_NE: + } + case ICmpInst::ICMP_NE: { if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max)) return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); + + // If all bits are known zero except for one, then we know at most one + // bit is set. If the comparison is against zero, then this is a check + // to see if *that* bit is set. + APInt Op0KnownZeroInverted = ~Op0KnownZero; + if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) { + // If the LHS is an AND with the same constant, look through it. + Value *LHS = 0; + ConstantInt *LHSC = 0; + if (!match(Op0, m_And(m_Value(LHS), m_ConstantInt(LHSC))) || + LHSC->getValue() != Op0KnownZeroInverted) + LHS = Op0; + + // If the LHS is 1 << x, and we know the result is a power of 2 like 8, + // then turn "((1 << x)&8) != 0" into "x != 3". + Value *X = 0; + if (match(LHS, m_Shl(m_One(), m_Value(X)))) { + unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros(); + return new ICmpInst(ICmpInst::ICMP_NE, X, + ConstantInt::get(X->getType(), CmpVal)); + } + + // If the LHS is 8 >>u x, and we know the result is a power of 2 like 1, + // then turn "((8 >>u x)&1) != 0" into "x != 3". + ConstantInt *CI = 0; + if (Op0KnownZeroInverted == 1 && + match(LHS, m_LShr(m_ConstantInt(CI), m_Value(X))) && + CI->getValue().isPowerOf2()) { + unsigned CmpVal = CI->getValue().countTrailingZeros(); + return new ICmpInst(ICmpInst::ICMP_NE, X, + ConstantInt::get(X->getType(), CmpVal)); + } + } + break; + } case ICmpInst::ICMP_ULT: if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B) return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); |