diff options
| -rw-r--r-- | lib/Transforms/Scalar/InstructionCombining.cpp | 39 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/load-cmp.ll | 11 |
2 files changed, 39 insertions, 11 deletions
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index 05da044e38..85ef7b18ef 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -6053,6 +6053,12 @@ FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV, // -2 -> overdef, >= 0 -> that index is false. int OnlyFalseElement = -1; + // MagicBitvector - This is a magic bitvector where we set a bit if the + // comparison is true for element 'i'. If there are 64 elements or less in + // the array, this will fully represent all the comparison results. + uint64_t MagicBitvector = 0; + + // Scan the array and see if one of our patterns matches. Constant *CompareRHS = cast<Constant>(ICI.getOperand(1)); for (unsigned i = 0, e = Init->getNumOperands(); i != e; ++i) { @@ -6080,8 +6086,12 @@ FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV, OnlyFalseElement = OnlyFalseElement == -1 ? i : -2; } + // If this element is in range, update our magic bitvector. + if (i < 64 && IsTrueForElt) + MagicBitvector |= 1 << i; + // If all of our states become overdefined, bail out early. - if (OnlyTrueElement == -2 && OnlyFalseElement == -2) + if (i >= 64 && OnlyTrueElement == -2 && OnlyFalseElement == -2) return 0; } @@ -6108,17 +6118,24 @@ FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV, OnlyFalseElement)); } - assert(0 && "Should have bailed out early"); - - // TODO: FCMP. - - // TODO: Range check. + // If a 32-bit or 64-bit magic bitvector captures the entire comparison state + // of this load, replace it with computation that does: + // ((magic_cst >> i) & 1) != 0 + if (Init->getNumOperands() <= 32 || + (TD && Init->getNumOperands() <= 64 && TD->isLegalInteger(64))) { + const Type *Ty; + if (Init->getNumOperands() <= 32) + Ty = Type::getInt32Ty(Init->getContext()); + else + Ty = Type::getInt64Ty(Init->getContext()); + Value *V = Builder->CreateIntCast(GEP->getOperand(2), Ty, false); + V = Builder->CreateLShr(ConstantInt::get(Ty, MagicBitvector), V); + V = Builder->CreateAnd(ConstantInt::get(Ty, 1), V); + return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0)); + } - // TODO: If the global array has 32 (or 64 if native!) or less entries, we - // can turn this into something like: - // ((magicbitconstant >> i) & 1) != 0) - // where we populate magicbitconstant with 0101010 based on the comparison - // results. + // TODO: Range check, two compares. + return 0; } diff --git a/test/Transforms/InstCombine/load-cmp.ll b/test/Transforms/InstCombine/load-cmp.ll index eac9ae495d..e44105791a 100644 --- a/test/Transforms/InstCombine/load-cmp.ll +++ b/test/Transforms/InstCombine/load-cmp.ll @@ -34,3 +34,14 @@ define i1 @test3(i32 %X) { ; CHECK-NEXT: ret i1 %R } +define i1 @test4(i32 %X) { + %P = getelementptr [10 x i16]* @G16, i32 0, i32 %X + %Q = load i16* %P + %R = icmp sle i16 %Q, 73 + ret i1 %R +; CHECK: @test4 +; CHECK-NEXT: lshr i32 933, %X +; CHECK-NEXT: and i32 {{.*}}, 1 +; CHECK-NEXT: %R = icmp ne i32 {{.*}}, 0 +; CHECK-NEXT: ret i1 %R +} |