[llvm] 077bff3 - [Analysis] isDereferenceableAndAlignedPointer(): recurse into select's hands

[Jordan Rupprecht via llvm-commits]

We're seeing a clang crash (Instruction does not dominate all uses) as a
result of this patch. With asserts enabled, I see:

assert.h assertion failed at llvm/lib/Analysis/LazyValueInfo.cpp:677 in
Optional<llvm::ValueLatticeElement> (anonymous
namespace)::LazyValueInfoImpl::solveBlockValueNonLocal(llvm::Value *,
llvm::BasicBlock *): isa<Argument>(Val) && "Unknown live-in to the entry
block"

Mind if we revert this patch while we come up with a reduction? And/or is
the error message above enough to clue you on what the right fix is?

The reproduction requires FDO, so reduction is trickier :( but I'll get
started

On Fri, Apr 9, 2021 at 4:56 PM Roman Lebedev via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

>
> Author: Roman Lebedev
> Date: 2021-04-10T00:56:28+03:00
> New Revision: 077bff39d46364035a5dcfa32fc69910ad0975d0
>
> URL:
> https://github.com/llvm/llvm-project/commit/077bff39d46364035a5dcfa32fc69910ad0975d0
> DIFF:
> https://github.com/llvm/llvm-project/commit/077bff39d46364035a5dcfa32fc69910ad0975d0.diff
>
> LOG: [Analysis] isDereferenceableAndAlignedPointer(): recurse into
> select's hands
>
> By doing this within the method itself,
> we support traversing multiple levels of selects (TODO: PHI's),
> fixing the SROA `std::clamp()` testcase.
>
> Fixes https://bugs.llvm.org/show_bug.cgi?id=47271
> Mostly fixes https://bugs.llvm.org/show_bug.cgi?id=49909
>
> Added:
>
>
> Modified:
>     llvm/lib/Analysis/Loads.cpp
>     llvm/test/Transforms/SROA/std-clamp.ll
>
> Removed:
>
>
>
>
> ################################################################################
> diff  --git a/llvm/lib/Analysis/Loads.cpp b/llvm/lib/Analysis/Loads.cpp
> index 8d01ea045097..2ae1fd5b5bde 100644
> --- a/llvm/lib/Analysis/Loads.cpp
> +++ b/llvm/lib/Analysis/Loads.cpp
> @@ -59,6 +59,16 @@ static bool isDereferenceableAndAlignedPointer(
>    // Note that it is not safe to speculate into a malloc'd region because
>    // malloc may return null.
>
> +  // Recurse into both hands of select.
> +  if (const SelectInst *Sel = dyn_cast<SelectInst>(V)) {
> +    return isDereferenceableAndAlignedPointer(Sel->getTrueValue(),
> Alignment,
> +                                              Size, DL, CtxI, DT, TLI,
> Visited,
> +                                              MaxDepth) &&
> +           isDereferenceableAndAlignedPointer(Sel->getFalseValue(),
> Alignment,
> +                                              Size, DL, CtxI, DT, TLI,
> Visited,
> +                                              MaxDepth);
> +  }
> +
>    // bitcast instructions are no-ops as far as dereferenceability is
> concerned.
>    if (const BitCastOperator *BC = dyn_cast<BitCastOperator>(V)) {
>      if (BC->getSrcTy()->isPointerTy())
>
> diff  --git a/llvm/test/Transforms/SROA/std-clamp.ll
> b/llvm/test/Transforms/SROA/std-clamp.ll
> index 561904252288..c0132a519722 100644
> --- a/llvm/test/Transforms/SROA/std-clamp.ll
> +++ b/llvm/test/Transforms/SROA/std-clamp.ll
> @@ -6,18 +6,14 @@ target datalayout =
> "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16
>  define float @_Z8stdclampfff(float %x, float %lo, float %hi) {
>  ; CHECK-LABEL: @_Z8stdclampfff(
>  ; CHECK-NEXT:  bb:
> -; CHECK-NEXT:    [[I:%.*]] = alloca float, align 4
> -; CHECK-NEXT:    [[I3:%.*]] = alloca float, align 4
>  ; CHECK-NEXT:    [[I4:%.*]] = alloca float, align 4
> -; CHECK-NEXT:    store float [[X:%.*]], float* [[I]], align 4
> -; CHECK-NEXT:    store float [[LO:%.*]], float* [[I3]], align 4
>  ; CHECK-NEXT:    store float [[HI:%.*]], float* [[I4]], align 4
> -; CHECK-NEXT:    [[I5:%.*]] = fcmp fast olt float [[X]], [[LO]]
> +; CHECK-NEXT:    [[I5:%.*]] = fcmp fast olt float [[X:%.*]], [[LO:%.*]]
>  ; CHECK-NEXT:    [[I6:%.*]] = fcmp fast olt float [[HI]], [[X]]
> -; CHECK-NEXT:    [[I7:%.*]] = select i1 [[I6]], float* [[I4]], float*
> [[I]]
> -; CHECK-NEXT:    [[I8:%.*]] = select i1 [[I5]], float* [[I3]], float*
> [[I7]]
> -; CHECK-NEXT:    [[I9:%.*]] = load float, float* [[I8]], align 4
> -; CHECK-NEXT:    ret float [[I9]]
> +; CHECK-NEXT:
> [[I9_SROA_SPECULATE_LOAD_FALSE_SROA_SPECULATE_LOAD_TRUE:%.*]] = load float,
> float* [[I4]], align 4
> +; CHECK-NEXT:    [[I9_SROA_SPECULATE_LOAD_FALSE_SROA_SPECULATED:%.*]] =
> select i1 [[I6]], float
> [[I9_SROA_SPECULATE_LOAD_FALSE_SROA_SPECULATE_LOAD_TRUE]], float [[X]]
> +; CHECK-NEXT:    [[I9_SROA_SPECULATED:%.*]] = select i1 [[I5]], float
> [[LO]], float [[I9_SROA_SPECULATE_LOAD_FALSE_SROA_SPECULATED]]
> +; CHECK-NEXT:    ret float [[I9_SROA_SPECULATED]]
>  ;
>  bb:
>    %i = alloca float, align 4
>
>
>
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