[llvm] r325466 - [PatternMatch, InstSimplify] enhance m_AllOnes() to ignore undef elements in vectors
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Sun Feb 18 10:31:37 PST 2018
Disregard the warning about the existing matchers. They're capturing the
APInt value, not the Constant wrapper object. That should be safe.
On Sun, Feb 18, 2018 at 11:05 AM, Sanjay Patel via llvm-commits <
llvm-commits at lists.llvm.org> wrote:
> Author: spatel
> Date: Sun Feb 18 10:05:08 2018
> New Revision: 325466
>
> URL: http://llvm.org/viewvc/llvm-project?rev=325466&view=rev
> Log:
> [PatternMatch, InstSimplify] enhance m_AllOnes() to ignore undef elements
> in vectors
>
> Loosening the matcher definition reveals a subtle bug in InstSimplify (we
> should not
> assume that because an operand constant matches that it's safe to return
> it as a result).
>
> So I'm making that change here too (that diff could be independent, but
> I'm not sure how
> to reveal it before the matcher change).
>
> This also seems like a good reason to *not* include matchers that capture
> the value.
> We don't want to encourage the potential misstep of propagating undef
> values when it's
> not allowed/intended.
>
> I didn't include the capture variant option here or in the related
> rL325437 (m_One),
> but it already exists for other constant matchers.
>
>
> Modified:
> llvm/trunk/include/llvm/IR/PatternMatch.h
> llvm/trunk/lib/Analysis/InstructionSimplify.cpp
> llvm/trunk/test/Transforms/InstSimplify/or.ll
> llvm/trunk/test/Transforms/InstSimplify/shr-nop.ll
>
> Modified: llvm/trunk/include/llvm/IR/PatternMatch.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/
> llvm/IR/PatternMatch.h?rev=325466&r1=325465&r2=325466&view=diff
> ============================================================
> ==================
> --- llvm/trunk/include/llvm/IR/PatternMatch.h (original)
> +++ llvm/trunk/include/llvm/IR/PatternMatch.h Sun Feb 18 10:05:08 2018
> @@ -182,17 +182,6 @@ struct match_nan {
> /// Match an arbitrary NaN constant. This includes quiet and signalling
> nans.
> inline match_nan m_NaN() { return match_nan(); }
>
> -struct match_all_ones {
> - template <typename ITy> bool match(ITy *V) {
> - if (const auto *C = dyn_cast<Constant>(V))
> - return C->isAllOnesValue();
> - return false;
> - }
> -};
> -
> -/// Match an integer or vector with all bits set to true.
> -inline match_all_ones m_AllOnes() { return match_all_ones(); }
> -
> struct match_sign_mask {
> template <typename ITy> bool match(ITy *V) {
> if (const auto *C = dyn_cast<Constant>(V))
> @@ -337,6 +326,14 @@ template <typename Predicate> struct api
> //
> ////////////////////////////////////////////////////////////
> ///////////////////
>
> +struct is_all_ones {
> + bool isValue(const APInt &C) { return C.isAllOnesValue(); }
> +};
> +/// Match an integer or vector with all bits set.
> +inline cst_pred_ty<is_all_ones> m_AllOnes() {
> + return cst_pred_ty<is_all_ones>();
> +}
> +
> struct is_maxsignedvalue {
> bool isValue(const APInt &C) { return C.isMaxSignedValue(); }
> };
>
> Modified: llvm/trunk/lib/Analysis/InstructionSimplify.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/
> Analysis/InstructionSimplify.cpp?rev=325466&r1=325465&r2=325466&view=diff
> ============================================================
> ==================
> --- llvm/trunk/lib/Analysis/InstructionSimplify.cpp (original)
> +++ llvm/trunk/lib/Analysis/InstructionSimplify.cpp Sun Feb 18 10:05:08
> 2018
> @@ -1264,9 +1264,10 @@ static Value *SimplifyAShrInst(Value *Op
> MaxRecurse))
> return V;
>
> - // all ones >>a X -> all ones
> + // all ones >>a X -> -1
> + // Do not return Op0 because it may contain undef elements if it's a
> vector.
> if (match(Op0, m_AllOnes()))
> - return Op0;
> + return Constant::getAllOnesValue(Op0->getType());
>
> // (X << A) >> A -> X
> Value *X;
> @@ -1783,21 +1784,16 @@ static Value *SimplifyOrInst(Value *Op0,
> return C;
>
> // X | undef -> -1
> - if (match(Op1, m_Undef()))
> + // X | -1 = -1
> + // Do not return Op1 because it may contain undef elements if it's a
> vector.
> + if (match(Op1, m_Undef()) || match(Op1, m_AllOnes()))
> return Constant::getAllOnesValue(Op0->getType());
>
> // X | X = X
> - if (Op0 == Op1)
> - return Op0;
> -
> // X | 0 = X
> - if (match(Op1, m_Zero()))
> + if (Op0 == Op1 || match(Op1, m_Zero()))
> return Op0;
>
> - // X | -1 = -1
> - if (match(Op1, m_AllOnes()))
> - return Op1;
> -
> // A | ~A = ~A | A = -1
> if (match(Op0, m_Not(m_Specific(Op1))) ||
> match(Op1, m_Not(m_Specific(Op0))))
>
> Modified: llvm/trunk/test/Transforms/InstSimplify/or.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Transforms/InstSimplify/or.ll?rev=325466&r1=325465&r2=325466&view=diff
> ============================================================
> ==================
> --- llvm/trunk/test/Transforms/InstSimplify/or.ll (original)
> +++ llvm/trunk/test/Transforms/InstSimplify/or.ll Sun Feb 18 10:05:08 2018
> @@ -19,8 +19,7 @@ define i32 @all_ones(i32 %A) {
>
> define <3 x i8> @all_ones_vec_with_undef_elt(<3 x i8> %A) {
> ; CHECK-LABEL: @all_ones_vec_with_undef_elt(
> -; CHECK-NEXT: [[B:%.*]] = or <3 x i8> [[A:%.*]], <i8 -1, i8 undef, i8
> -1>
> -; CHECK-NEXT: ret <3 x i8> [[B]]
> +; CHECK-NEXT: ret <3 x i8> <i8 -1, i8 -1, i8 -1>
> ;
> %B = or <3 x i8> %A, <i8 -1, i8 undef, i8 -1>
> ret <3 x i8> %B
>
> Modified: llvm/trunk/test/Transforms/InstSimplify/shr-nop.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Transforms/InstSimplify/shr-nop.ll?rev=325466&r1=325465&
> r2=325466&view=diff
> ============================================================
> ==================
> --- llvm/trunk/test/Transforms/InstSimplify/shr-nop.ll (original)
> +++ llvm/trunk/test/Transforms/InstSimplify/shr-nop.ll Sun Feb 18
> 10:05:08 2018
> @@ -195,8 +195,7 @@ define i1 @ashr_ne_first_zero(i8 %a) {
>
> define <3 x i8> @ashr_all_ones_vec_with_undef_elts(<3 x i8> %x, <3 x i8>
> %y) {
> ; CHECK-LABEL: @ashr_all_ones_vec_with_undef_elts(
> -; CHECK-NEXT: [[SH:%.*]] = ashr <3 x i8> <i8 undef, i8 -1, i8 undef>,
> [[Y:%.*]]
> -; CHECK-NEXT: ret <3 x i8> [[SH]]
> +; CHECK-NEXT: ret <3 x i8> <i8 -1, i8 -1, i8 -1>
> ;
> %sh = ashr <3 x i8> <i8 undef, i8 -1, i8 undef>, %y
> ret <3 x i8> %sh
>
>
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