diff options
Diffstat (limited to 'llvm/lib/Transforms')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp | 74 |
1 files changed, 72 insertions, 2 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index 617d8e7a5c1..2a87f8ab3be 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -1319,10 +1319,80 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI, } case Instruction::Shl: { // (icmp pred (shl X, ShAmt), CI) + uint32_t TypeBits = RHSV.getBitWidth(); ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1)); - if (!ShAmt) break; + if (!ShAmt) { + Value *X; + // (1 << X) pred P2 -> X pred Log2(P2) + if (match(LHSI, m_Shl(m_One(), m_Value(X)))) { + bool RHSVIsPowerOf2 = RHSV.isPowerOf2(); + ICmpInst::Predicate Pred = ICI.getPredicate(); + if (ICI.isUnsigned()) { + if (!RHSVIsPowerOf2) { + // (1 << X) < 30 -> X <= 4 + // (1 << X) <= 30 -> X <= 4 + // (1 << X) >= 30 -> X > 4 + // (1 << X) > 30 -> X > 4 + if (Pred == ICmpInst::ICMP_ULT) + Pred = ICmpInst::ICMP_ULE; + else if (Pred == ICmpInst::ICMP_UGE) + Pred = ICmpInst::ICMP_UGT; + } + unsigned RHSLog2 = RHSV.logBase2(); + + // (1 << X) >= 2147483648 -> X >= 31 -> X == 31 + // (1 << X) > 2147483648 -> X > 31 -> false + // (1 << X) <= 2147483648 -> X <= 31 -> true + // (1 << X) < 2147483648 -> X < 31 -> X != 31 + if (RHSLog2 == TypeBits-1) { + if (Pred == ICmpInst::ICMP_UGE) + Pred = ICmpInst::ICMP_EQ; + else if (Pred == ICmpInst::ICMP_UGT) + return ReplaceInstUsesWith(ICI, Builder->getFalse()); + else if (Pred == ICmpInst::ICMP_ULE) + return ReplaceInstUsesWith(ICI, Builder->getTrue()); + else if (Pred == ICmpInst::ICMP_ULT) + Pred = ICmpInst::ICMP_NE; + } - uint32_t TypeBits = RHSV.getBitWidth(); + return new ICmpInst(Pred, X, + ConstantInt::get(RHS->getType(), RHSLog2)); + } else if (ICI.isSigned()) { + if (RHSV.isAllOnesValue()) { + // (1 << X) <= -1 -> X == 31 + if (Pred == ICmpInst::ICMP_SLE) + return new ICmpInst(ICmpInst::ICMP_EQ, X, + ConstantInt::get(RHS->getType(), TypeBits-1)); + + // (1 << X) > -1 -> X != 31 + if (Pred == ICmpInst::ICMP_SGT) + return new ICmpInst(ICmpInst::ICMP_NE, X, + ConstantInt::get(RHS->getType(), TypeBits-1)); + } else if (!RHSV) { + // (1 << X) < 0 -> X == 31 + // (1 << X) <= 0 -> X == 31 + if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE) + return new ICmpInst(ICmpInst::ICMP_EQ, X, + ConstantInt::get(RHS->getType(), TypeBits-1)); + + // (1 << X) >= 0 -> X != 31 + // (1 << X) > 0 -> X != 31 + if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE) + return new ICmpInst(ICmpInst::ICMP_NE, X, + ConstantInt::get(RHS->getType(), TypeBits-1)); + } + } else if (ICI.isEquality()) { + if (RHSVIsPowerOf2) + return new ICmpInst( + Pred, X, ConstantInt::get(RHS->getType(), RHSV.logBase2())); + + return ReplaceInstUsesWith( + ICI, Pred == ICmpInst::ICMP_EQ ? Builder->getFalse() + : Builder->getTrue()); + } + } + break; + } // Check that the shift amount is in range. If not, don't perform // undefined shifts. When the shift is visited it will be |
