[llvm] r290786 - [ValueTracking] make dominator tree requirement explicit for isKnownNonNullFromDominatingCondition(); NFCI
Davide Italiano via llvm-commits
llvm-commits at lists.llvm.org
Sat Dec 31 09:58:08 PST 2016
On Sat, Dec 31, 2016 at 9:37 AM, Sanjay Patel via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: spatel
> Date: Sat Dec 31 11:37:01 2016
> New Revision: 290786
>
> URL: http://llvm.org/viewvc/llvm-project?rev=290786&view=rev
> Log:
> [ValueTracking] make dominator tree requirement explicit for isKnownNonNullFromDominatingCondition(); NFCI
>
> I don't think this hole is currently exposed, but I crashed regression tests for
> jump-threading and loop-vectorize after I added calls to isKnownNonNullAt() in
> InstSimplify as part of trying to solve PR28430:
> https://llvm.org/bugs/show_bug.cgi?id=28430
>
> That's because they call into value tracking with a context instruction, but no
> other parts of the query structure filled in.
>
> For more background, see the discussion in:
> https://reviews.llvm.org/D27855
>
> Modified:
> llvm/trunk/include/llvm/Analysis/ValueTracking.h
> llvm/trunk/lib/Analysis/ValueTracking.cpp
>
> Modified: llvm/trunk/include/llvm/Analysis/ValueTracking.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/ValueTracking.h?rev=290786&r1=290785&r2=290786&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/Analysis/ValueTracking.h (original)
> +++ llvm/trunk/include/llvm/Analysis/ValueTracking.h Sat Dec 31 11:37:01 2016
> @@ -308,12 +308,12 @@ template <typename T> class ArrayRef;
> bool isKnownNonNull(const Value *V);
>
> /// Return true if this pointer couldn't possibly be null. If the context
> - /// instruction is specified, perform context-sensitive analysis and return
> - /// true if the pointer couldn't possibly be null at the specified
> - /// instruction.
> + /// instruction and dominator tree are specified, perform context-sensitive
> + /// analysis and return true if the pointer couldn't possibly be null at the
> + /// specified instruction.
> bool isKnownNonNullAt(const Value *V,
> const Instruction *CtxI = nullptr,
> - const DominatorTree *DT = nullptr);
> + const DominatorTree *DT = nullptr);
>
> /// Return true if it is valid to use the assumptions provided by an
> /// assume intrinsic, I, at the point in the control-flow identified by the
>
> Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=290786&r1=290785&r2=290786&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
> +++ llvm/trunk/lib/Analysis/ValueTracking.cpp Sat Dec 31 11:37:01 2016
> @@ -3368,6 +3368,8 @@ static bool isKnownNonNullFromDominating
> const DominatorTree *DT) {
> assert(V->getType()->isPointerTy() && "V must be pointer type");
> assert(!isa<ConstantData>(V) && "Did not expect ConstantPointerNull");
> + assert(CtxI && "Context instruction required for analysis");
> + assert(DT && "Dominator tree required for analysis");
>
> unsigned NumUsesExplored = 0;
> for (auto *U : V->users()) {
> @@ -3410,7 +3412,10 @@ bool llvm::isKnownNonNullAt(const Value
> if (isKnownNonNull(V))
> return true;
>
> - return CtxI ? ::isKnownNonNullFromDominatingCondition(V, CtxI, DT) : false;
> + if (!CtxI || !DT)
> + return false;
> +
How hard is to guarantee that we always have a valid/updated dominator
when we get here (i.e. we don't need to bail out)?
--
Davide
"There are no solved problems; there are only problems that are more
or less solved" -- Henri Poincare
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