Author: Roman Lebedev Date: 2021-05-19T20:01:56-07:00 New Revision: 4973ce53ca8abfc14233a3d8b3045673e0e8543c
URL: https://github.com/llvm/llvm-project/commit/4973ce53ca8abfc14233a3d8b3045673e0e8543c DIFF: https://github.com/llvm/llvm-project/commit/4973ce53ca8abfc14233a3d8b3045673e0e8543c.diff LOG: ~(C + X) --> ~C - X (PR50308) We can not rely on (C+X)-->(X+C) already happening, because we might not have visited that `add` yet. The added testcase would get stuck in an endless combine loop. (cherry-picked from 554b1bced325) Added: Modified: llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp llvm/test/Transforms/InstCombine/not-add.ll Removed: ################################################################################ diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp index 68c4156af2c42..85a7abe211b3c 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp @@ -3221,11 +3221,6 @@ Instruction *InstCombinerImpl::visitXor(BinaryOperator &I) { } } - // ~(X - Y) --> ~X + Y - if (match(NotVal, m_Sub(m_Value(X), m_Value(Y)))) - if (isa<Constant>(X) || NotVal->hasOneUse()) - return BinaryOperator::CreateAdd(Builder.CreateNot(X), Y); - // ~(~X >>s Y) --> (X >>s Y) if (match(NotVal, m_AShr(m_Not(m_Value(X)), m_Value(Y)))) return BinaryOperator::CreateAShr(X, Y); @@ -3256,9 +3251,15 @@ Instruction *InstCombinerImpl::visitXor(BinaryOperator &I) { return BinaryOperator::CreateAShr(ConstantExpr::getNot(C), Y); } - // ~(X + C) --> -(C + 1) - X - if (match(Op0, m_Add(m_Value(X), m_Constant(C)))) - return BinaryOperator::CreateSub(ConstantExpr::getNeg(AddOne(C)), X); + // ~(X + C) --> ~C - X + if (match(NotVal, m_c_Add(m_Value(X), m_ImmConstant(C)))) + return BinaryOperator::CreateSub(ConstantExpr::getNot(C), X); + + // ~(X - Y) --> ~X + Y + // FIXME: is it really beneficial to sink the `not` here? + if (match(NotVal, m_Sub(m_Value(X), m_Value(Y)))) + if (isa<Constant>(X) || NotVal->hasOneUse()) + return BinaryOperator::CreateAdd(Builder.CreateNot(X), Y); // ~(~X + Y) --> X - Y if (match(NotVal, m_c_Add(m_Not(m_Value(X)), m_Value(Y)))) diff --git a/llvm/test/Transforms/InstCombine/not-add.ll b/llvm/test/Transforms/InstCombine/not-add.ll index 6891fdd5fcc54..d372e7603724b 100644 --- a/llvm/test/Transforms/InstCombine/not-add.ll +++ b/llvm/test/Transforms/InstCombine/not-add.ll @@ -137,3 +137,31 @@ define <4 x i32> @vector_test_undef_nsw_nuw(<4 x i32> %x, <4 x i32> %y) { %nota = xor <4 x i32> %a, <i32 -1, i32 -1, i32 undef, i32 undef> ret <4 x i32> %nota } + +define i32 @pr50308(i1 %c1, i32 %v1, i32 %v2, i32 %v3) { +; CHECK-LABEL: @pr50308( +; CHECK-NEXT: entry: +; CHECK-NEXT: br i1 [[C1:%.*]], label [[COND_TRUE:%.*]], label [[COND_END:%.*]] +; CHECK: cond.true: +; CHECK-NEXT: [[ADD_NOT:%.*]] = sub i32 -2, [[V1:%.*]] +; CHECK-NEXT: [[ADD1_NEG:%.*]] = xor i32 [[ADD_NOT]], [[V2:%.*]] +; CHECK-NEXT: br label [[COND_END]] +; CHECK: cond.end: +; CHECK-NEXT: [[COND_NEG:%.*]] = phi i32 [ [[ADD1_NEG]], [[COND_TRUE]] ], [ 0, [[ENTRY:%.*]] ] +; CHECK-NEXT: [[SUB:%.*]] = add i32 [[COND_NEG]], [[V3:%.*]] +; CHECK-NEXT: ret i32 [[SUB]] +; +entry: + br i1 %c1, label %cond.true, label %cond.end + +cond.true: + %add = add nsw i32 1, %v1 + %xor = xor i32 %add, %v2 + %add1 = add nsw i32 1, %xor + br label %cond.end + +cond.end: + %cond = phi i32 [ %add1, %cond.true ], [ 0, %entry ] + %sub = sub nsw i32 %v3, %cond + ret i32 %sub +} _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
