diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index 5b412a52e1644..e71f3e113b96e 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -1962,6 +1962,17 @@ Instruction *InstCombinerImpl::foldICmpAndConstant(ICmpInst &Cmp, return BinaryOperator::CreateAnd(TruncY, X); } + // (icmp eq/ne (and (shl -1, X), Y), 0) + // -> (icmp eq/ne (lshr Y, X), 0) + // We could technically handle any C == 0 or (C < 0 && isOdd(C)) but it seems + // highly unlikely the non-zero case will ever show up in code. + if (C.isZero() && + match(And, m_OneUse(m_c_And(m_OneUse(m_Shl(m_AllOnes(), m_Value(X))), + m_Value(Y))))) { + Value *LShr = Builder.CreateLShr(Y, X); + return new ICmpInst(Pred, LShr, Constant::getNullValue(LShr->getType())); + } + return nullptr; } diff --git a/llvm/test/Transforms/InstCombine/icmp-and-shift.ll b/llvm/test/Transforms/InstCombine/icmp-and-shift.ll index b0d4dabb73840..08d23e84c3960 100644 --- a/llvm/test/Transforms/InstCombine/icmp-and-shift.ll +++ b/llvm/test/Transforms/InstCombine/icmp-and-shift.ll @@ -520,3 +520,89 @@ define i1 @slt_and_shl_one(i8 %x, i8 %y) { %cmp = icmp slt i8 %and, %pow2 ret i1 %cmp } + +define i1 @fold_eq_lhs(i8 %x, i8 %y) { +; CHECK-LABEL: @fold_eq_lhs( +; CHECK-NEXT: [[AND:%.*]] = lshr i8 [[Y:%.*]], [[X:%.*]] +; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[AND]], 0 +; CHECK-NEXT: ret i1 [[R]] +; + %shl = shl i8 -1, %x + %and = and i8 %shl, %y + %r = icmp eq i8 %and, 0 + ret i1 %r +} + +define i1 @fold_eq_lhs_fail_eq_nonzero(i8 %x, i8 %y) { +; CHECK-LABEL: @fold_eq_lhs_fail_eq_nonzero( +; CHECK-NEXT: [[SHL:%.*]] = shl nsw i8 -1, [[X:%.*]] +; CHECK-NEXT: [[AND:%.*]] = and i8 [[SHL]], [[Y:%.*]] +; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[AND]], 1 +; CHECK-NEXT: ret i1 [[R]] +; + %shl = shl i8 -1, %x + %and = and i8 %shl, %y + %r = icmp eq i8 %and, 1 + ret i1 %r +} + +define i1 @fold_eq_lhs_fail_multiuse_shl(i8 %x, i8 %y) { +; CHECK-LABEL: @fold_eq_lhs_fail_multiuse_shl( +; CHECK-NEXT: [[SHL:%.*]] = shl nsw i8 -1, [[X:%.*]] +; CHECK-NEXT: call void @use(i8 [[SHL]]) +; CHECK-NEXT: [[AND:%.*]] = and i8 [[SHL]], [[Y:%.*]] +; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[AND]], 0 +; CHECK-NEXT: ret i1 [[R]] +; + %shl = shl i8 -1, %x + call void @use(i8 %shl) + %and = and i8 %shl, %y + %r = icmp eq i8 %and, 0 + ret i1 %r +} + +define i1 @fold_ne_rhs(i8 %x, i8 %yy) { +; CHECK-LABEL: @fold_ne_rhs( +; CHECK-NEXT: [[Y:%.*]] = xor i8 [[YY:%.*]], 123 +; CHECK-NEXT: [[AND:%.*]] = lshr i8 [[Y]], [[X:%.*]] +; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[AND]], 0 +; CHECK-NEXT: ret i1 [[R]] +; + %y = xor i8 %yy, 123 + %shl = shl i8 -1, %x + %and = and i8 %y, %shl + %r = icmp ne i8 %and, 0 + ret i1 %r +} + +define i1 @fold_ne_rhs_fail_multiuse_and(i8 %x, i8 %yy) { +; CHECK-LABEL: @fold_ne_rhs_fail_multiuse_and( +; CHECK-NEXT: [[Y:%.*]] = xor i8 [[YY:%.*]], 123 +; CHECK-NEXT: [[SHL:%.*]] = shl nsw i8 -1, [[X:%.*]] +; CHECK-NEXT: [[AND:%.*]] = and i8 [[Y]], [[SHL]] +; CHECK-NEXT: call void @use(i8 [[AND]]) +; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[AND]], 0 +; CHECK-NEXT: ret i1 [[R]] +; + %y = xor i8 %yy, 123 + %shl = shl i8 -1, %x + %and = and i8 %y, %shl + call void @use(i8 %and) + %r = icmp ne i8 %and, 0 + ret i1 %r +} + +define i1 @fold_ne_rhs_fail_shift_not_1s(i8 %x, i8 %yy) { +; CHECK-LABEL: @fold_ne_rhs_fail_shift_not_1s( +; CHECK-NEXT: [[Y:%.*]] = xor i8 [[YY:%.*]], 122 +; CHECK-NEXT: [[SHL:%.*]] = shl i8 -2, [[X:%.*]] +; CHECK-NEXT: [[AND:%.*]] = and i8 [[Y]], [[SHL]] +; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[AND]], 0 +; CHECK-NEXT: ret i1 [[R]] +; + %y = xor i8 %yy, 123 + %shl = shl i8 -2, %x + %and = and i8 %y, %shl + %r = icmp ne i8 %and, 0 + ret i1 %r +}