diff options
| -rw-r--r-- | lib/Target/README.txt | 38 | ||||
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineCompares.cpp | 15 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/icmp.ll | 30 |
3 files changed, 45 insertions, 38 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index 52a334a6174..282d9234c1a 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -1844,44 +1844,6 @@ we remove checking in code like //===---------------------------------------------------------------------===// -This code (from Benchmarks/Dhrystone/dry.c): - -define i32 @Func1(i32, i32) nounwind readnone optsize ssp { -entry: - %sext = shl i32 %0, 24 - %conv = ashr i32 %sext, 24 - %sext6 = shl i32 %1, 24 - %conv4 = ashr i32 %sext6, 24 - %cmp = icmp eq i32 %conv, %conv4 - %. = select i1 %cmp, i32 10000, i32 0 - ret i32 %. -} - -Should be simplified into something like: - -define i32 @Func1(i32, i32) nounwind readnone optsize ssp { -entry: - %sext = shl i32 %0, 24 - %conv = and i32 %sext, 0xFF000000 - %sext6 = shl i32 %1, 24 - %conv4 = and i32 %sext6, 0xFF000000 - %cmp = icmp eq i32 %conv, %conv4 - %. = select i1 %cmp, i32 10000, i32 0 - ret i32 %. -} - -and then to: - -define i32 @Func1(i32, i32) nounwind readnone optsize ssp { -entry: - %conv = and i32 %0, 0xFF - %conv4 = and i32 %1, 0xFF - %cmp = icmp eq i32 %conv, %conv4 - %. = select i1 %cmp, i32 10000, i32 0 - ret i32 %. -} -//===---------------------------------------------------------------------===// - clang -O3 currently compiles this code int g(unsigned int a) { diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp index 3434a62d9e1..803b50a88e5 100644 --- a/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -3553,6 +3553,21 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) { } } + // (A << C) == (B << C) --> ((A^B) & (~0U >> C)) == 0 + if (match(Op0, m_OneUse(m_Shl(m_Value(A), m_ConstantInt(Cst1)))) && + match(Op1, m_OneUse(m_Shl(m_Value(B), m_Specific(Cst1))))) { + unsigned TypeBits = Cst1->getBitWidth(); + unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits); + if (ShAmt < TypeBits && ShAmt != 0) { + Value *Xor = Builder->CreateXor(A, B, I.getName() + ".unshifted"); + APInt AndVal = APInt::getLowBitsSet(TypeBits, TypeBits - ShAmt); + Value *And = Builder->CreateAnd(Xor, Builder->getInt(AndVal), + I.getName() + ".mask"); + return new ICmpInst(I.getPredicate(), And, + Constant::getNullValue(Cst1->getType())); + } + } + // Transform "icmp eq (trunc (lshr(X, cst1)), cst" to // "icmp (and X, mask), cst" uint64_t ShAmt = 0; diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll index dd109837a40..edcf76d5a7d 100644 --- a/test/Transforms/InstCombine/icmp.ll +++ b/test/Transforms/InstCombine/icmp.ll @@ -1573,3 +1573,33 @@ define i32 @f5(i8 %a, i8 %b) { %sub7.sub = select i1 %cmp4, i32 %sub7, i32 %sub ret i32 %sub7.sub } + +; CHECK-LABEL: @f6 +; CHECK: %cmp.unshifted = xor i32 %a, %b +; CHECK-NEXT: %cmp.mask = and i32 %cmp.unshifted, 255 +; CHECK-NEXT: %cmp = icmp eq i32 %cmp.mask, 0 +; CHECK-NEXT: %s = select i1 %cmp, i32 10000, i32 0 +; CHECK-NEXT: ret i32 %s +define i32 @f6(i32 %a, i32 %b) { + %sext = shl i32 %a, 24 + %conv = ashr i32 %sext, 24 + %sext6 = shl i32 %b, 24 + %conv4 = ashr i32 %sext6, 24 + %cmp = icmp eq i32 %conv, %conv4 + %s = select i1 %cmp, i32 10000, i32 0 + ret i32 %s +} + +; CHECK-LABEL: @f7 +; CHECK: %cmp.unshifted = xor i32 %a, %b +; CHECK-NEXT: %cmp.mask = and i32 %cmp.unshifted, 511 +; CHECK-NEXT: %cmp = icmp ne i32 %cmp.mask, 0 +; CHECK-NEXT: %s = select i1 %cmp, i32 10000, i32 0 +; CHECK-NEXT: ret i32 %s +define i32 @f7(i32 %a, i32 %b) { + %sext = shl i32 %a, 23 + %sext6 = shl i32 %b, 23 + %cmp = icmp ne i32 %sext, %sext6 + %s = select i1 %cmp, i32 10000, i32 0 + ret i32 %s +} |