diff options
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstructionCombining.cpp | 16 | ||||
| -rw-r--r-- | llvm/test/Transforms/InstCombine/vec_shuffle.ll | 12 |
2 files changed, 22 insertions, 6 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp index 13903d16529..7c9dbcb66cc 100644 --- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp +++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp @@ -1455,6 +1455,22 @@ Instruction *InstCombiner::foldVectorBinop(BinaryOperator &Inst) { } NewVecC[ShMask[I]] = CElt; } + // If this is a widening shuffle, we must be able to extend with undef + // elements. If the original binop does not produce an undef in the high + // lanes, then this transform is not safe. + // TODO: We could shuffle those non-undef constant values into the + // result by using a constant vector (rather than an undef vector) + // as operand 1 of the new binop, but that might be too aggressive + // for target-independent shuffle creation. + if (I >= SrcVecNumElts) { + Constant *MaybeUndef = + ConstOp1 ? ConstantExpr::get(Opcode, UndefScalar, CElt) + : ConstantExpr::get(Opcode, CElt, UndefScalar); + if (!isa<UndefValue>(MaybeUndef)) { + MayChange = false; + break; + } + } } if (MayChange) { Constant *NewC = ConstantVector::get(NewVecC); diff --git a/llvm/test/Transforms/InstCombine/vec_shuffle.ll b/llvm/test/Transforms/InstCombine/vec_shuffle.ll index 6e500451828..b82c8117eeb 100644 --- a/llvm/test/Transforms/InstCombine/vec_shuffle.ll +++ b/llvm/test/Transforms/InstCombine/vec_shuffle.ll @@ -633,13 +633,13 @@ define <4 x i16> @widening_shuffle_shl_constant_op1(<2 x i16> %v) { ret <4 x i16> %bo } -; FIXME: A binop that does not produce undef in the high lanes can not be moved before the shuffle. +; A binop that does not produce undef in the high lanes can not be moved before the shuffle. ; This is not ok because 'shl undef, 1 (or 2)' --> 0' but moving the shuffle results in undef instead. define <4 x i16> @widening_shuffle_shl_constant_op1_non0(<2 x i16> %v) { ; CHECK-LABEL: @widening_shuffle_shl_constant_op1_non0( -; CHECK-NEXT: [[TMP1:%.*]] = shl <2 x i16> [[V:%.*]], <i16 2, i16 4> -; CHECK-NEXT: [[BO:%.*]] = shufflevector <2 x i16> [[TMP1]], <2 x i16> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef> +; CHECK-NEXT: [[SHUF:%.*]] = shufflevector <2 x i16> [[V:%.*]], <2 x i16> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef> +; CHECK-NEXT: [[BO:%.*]] = shl <4 x i16> [[SHUF]], <i16 2, i16 4, i16 1, i16 2> ; CHECK-NEXT: ret <4 x i16> [[BO]] ; %shuf = shufflevector <2 x i16> %v, <2 x i16> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef> @@ -647,13 +647,13 @@ define <4 x i16> @widening_shuffle_shl_constant_op1_non0(<2 x i16> %v) { ret <4 x i16> %bo } -; FIXME: A binop that does not produce undef in the high lanes can not be moved before the shuffle. +; A binop that does not produce undef in the high lanes can not be moved before the shuffle. ; This is not ok because 'or -1, undef --> -1' but moving the shuffle results in undef instead. define <4 x i16> @widening_shuffle_or(<2 x i16> %v) { ; CHECK-LABEL: @widening_shuffle_or( -; CHECK-NEXT: [[TMP1:%.*]] = or <2 x i16> [[V:%.*]], <i16 42, i16 -42> -; CHECK-NEXT: [[BO:%.*]] = shufflevector <2 x i16> [[TMP1]], <2 x i16> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef> +; CHECK-NEXT: [[SHUF:%.*]] = shufflevector <2 x i16> [[V:%.*]], <2 x i16> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef> +; CHECK-NEXT: [[BO:%.*]] = or <4 x i16> [[SHUF]], <i16 42, i16 -42, i16 -1, i16 -1> ; CHECK-NEXT: ret <4 x i16> [[BO]] ; %shuf = shufflevector <2 x i16> %v, <2 x i16> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef> |
