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<div class="moz-cite-prefix">On 3/23/21 2:35 PM, Nikita Popov wrote:<br>
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<blockquote type="cite"
cite="mid:CAF+90c8kNCMf3rsg1rNy2tmsJKg=DZ1Nae2NAbFBBFjS-YPShg@mail.gmail.com">
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<div dir="ltr" class="gmail_attr">On Tue, Mar 23, 2021 at
10:21 PM Philip Reames <<a
href="mailto:listmail@philipreames.com"
moz-do-not-send="true">listmail@philipreames.com</a>>
wrote:<br>
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<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">This doesn't seem like
the right fix. We conservatively report operand <br>
bundles allowing reads for *unknown* bundle types. The
assume bundle <br>
type should have well defined semantics and could be
explicitly whitelisted.<br>
<br>
Philip<br>
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<div>I believe the assume operand bundles are somewhat special
and distinct from other bundles, in that they only apply to
assumes, and in that they are not explicitly enumerated. An
operand bundle on an assume simply corresponds to the
attribute of the same name.<br>
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Right, that's my point. See isFnAttrDisallowedByOpBundle and
callees on CallBase. You should be able to simply add explicit
handling for assume bundle there and everything "should work". <br>
<blockquote type="cite"
cite="mid:CAF+90c8kNCMf3rsg1rNy2tmsJKg=DZ1Nae2NAbFBBFjS-YPShg@mail.gmail.com">
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<div>Regards,</div>
<div>Nikita<br>
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<div> </div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
On 3/23/21 1:21 PM, Nikita Popov via llvm-commits wrote:<br>
> Author: Nikita Popov<br>
> Date: 2021-03-23T21:21:19+01:00<br>
> New Revision: 931b6066acc597e680b8df25521a2f83b40dfaae<br>
><br>
> URL: <a
href="https://github.com/llvm/llvm-project/commit/931b6066acc597e680b8df25521a2f83b40dfaae"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://github.com/llvm/llvm-project/commit/931b6066acc597e680b8df25521a2f83b40dfaae</a><br>
> DIFF: <a
href="https://github.com/llvm/llvm-project/commit/931b6066acc597e680b8df25521a2f83b40dfaae.diff"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://github.com/llvm/llvm-project/commit/931b6066acc597e680b8df25521a2f83b40dfaae.diff</a><br>
><br>
> LOG: [BasicAA] Handle assumes with operand bundles<br>
><br>
> This fixes a regression reported on D99022: If a call
has operand<br>
> bundles, then the inaccessiblememonly attribute on the
function<br>
> will be ignored, as operand bundles can affect modref
behavior in<br>
> the general case. However, for assume operand bundles
in particular<br>
> this is not the case.<br>
><br>
> Adjust getModRefBehavior() to always report
inaccessiblememonly<br>
> for assumes, regardless of presence of operand bundles.<br>
><br>
> Added:<br>
> <br>
><br>
> Modified:<br>
> llvm/lib/Analysis/BasicAliasAnalysis.cpp<br>
> llvm/test/Analysis/BasicAA/assume.ll<br>
><br>
> Removed:<br>
> <br>
><br>
><br>
>
################################################################################<br>
> diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
b/llvm/lib/Analysis/BasicAliasAnalysis.cpp<br>
> index 86362f770e2d4..65117d82a81ce 100644<br>
> --- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp<br>
> +++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp<br>
> @@ -672,12 +672,22 @@ bool
BasicAAResult::pointsToConstantMemory(const MemoryLocation
&Loc,<br>
> return Worklist.empty();<br>
> }<br>
> <br>
> +static bool isIntrinsicCall(const CallBase *Call,
Intrinsic::ID IID) {<br>
> + const IntrinsicInst *II =
dyn_cast<IntrinsicInst>(Call);<br>
> + return II && II->getIntrinsicID() == IID;<br>
> +}<br>
> +<br>
> /// Returns the behavior when calling the given call
site.<br>
> FunctionModRefBehavior
BasicAAResult::getModRefBehavior(const CallBase *Call) {<br>
> if (Call->doesNotAccessMemory())<br>
> // Can't do better than this.<br>
> return FMRB_DoesNotAccessMemory;<br>
> <br>
> + // The assume intrinsic can have operand bundles,
but still only accesses<br>
> + // inaccessible memory in that case (to maintain
control dependencies).<br>
> + if (isIntrinsicCall(Call, Intrinsic::assume))<br>
> + return FMRB_OnlyAccessesInaccessibleMem;<br>
> +<br>
> FunctionModRefBehavior Min =
FMRB_UnknownModRefBehavior;<br>
> <br>
> // If the callsite knows it only reads memory,
don't return worse<br>
> @@ -771,11 +781,6 @@ ModRefInfo
BasicAAResult::getArgModRefInfo(const CallBase *Call,<br>
> return AAResultBase::getArgModRefInfo(Call,
ArgIdx);<br>
> }<br>
> <br>
> -static bool isIntrinsicCall(const CallBase *Call,
Intrinsic::ID IID) {<br>
> - const IntrinsicInst *II =
dyn_cast<IntrinsicInst>(Call);<br>
> - return II && II->getIntrinsicID() == IID;<br>
> -}<br>
> -<br>
> #ifndef NDEBUG<br>
> static const Function *getParent(const Value *V) {<br>
> if (const Instruction *inst =
dyn_cast<Instruction>(V)) {<br>
><br>
> diff --git a/llvm/test/Analysis/BasicAA/assume.ll
b/llvm/test/Analysis/BasicAA/assume.ll<br>
> index 4b268836cc49e..bc6be3ef0157e 100644<br>
> --- a/llvm/test/Analysis/BasicAA/assume.ll<br>
> +++ b/llvm/test/Analysis/BasicAA/assume.ll<br>
> @@ -29,12 +29,12 @@ define void @test2(i8* %P, i8* %Q)
nounwind ssp {<br>
> ; CHECK-LABEL: Function: test2:<br>
> <br>
> ; CHECK: MayAlias: i8* %P, i8* %Q<br>
> -; CHECK: Both ModRef: Ptr: i8* %P <-> tail
call void @llvm.assume(i1 true) [ "nonnull"(i8* %P) ]<br>
> -; CHECK: Both ModRef: Ptr: i8* %Q <-> tail
call void @llvm.assume(i1 true) [ "nonnull"(i8* %P) ]<br>
> +; CHECK: NoModRef: Ptr: i8* %P <-> tail
call void @llvm.assume(i1 true) [ "nonnull"(i8* %P) ]<br>
> +; CHECK: NoModRef: Ptr: i8* %Q <-> tail
call void @llvm.assume(i1 true) [ "nonnull"(i8* %P) ]<br>
> ; CHECK: Both ModRef: Ptr: i8* %P <-> tail
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12,
i1 false)<br>
> ; CHECK: Both ModRef: Ptr: i8* %Q <-> tail
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12,
i1 false)<br>
> -; CHECK: Both ModRef: tail call void @llvm.assume(i1
true) [ "nonnull"(i8* %P) ] <-> tail call void
@llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i1 false)<br>
> -; CHECK: Both ModRef: tail call void
@llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i1 false)
<-> tail call void @llvm.assume(i1 true) [
"nonnull"(i8* %P) ]<br>
> +; CHECK: NoModRef: tail call void @llvm.assume(i1
true) [ "nonnull"(i8* %P) ] <-> tail call void
@llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i1 false)<br>
> +; CHECK: NoModRef: tail call void
@llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i1 false)
<-> tail call void @llvm.assume(i1 true) [
"nonnull"(i8* %P) ]<br>
> }<br>
> <br>
> attributes #0 = { nounwind }<br>
><br>
><br>
> <br>
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