<div dir="ltr">We're seeing a clang crash (Instruction does not dominate all uses) as a result of this patch. With asserts enabled, I see:<div><br></div><div>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"<br></div><div><br></div><div>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?</div><div><br></div><div>The reproduction requires FDO, so reduction is trickier :( but I'll get started</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Apr 9, 2021 at 4:56 PM Roman Lebedev via llvm-commits <<a href="mailto:llvm-commits@lists.llvm.org">llvm-commits@lists.llvm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><br>
Author: Roman Lebedev<br>
Date: 2021-04-10T00:56:28+03:00<br>
New Revision: 077bff39d46364035a5dcfa32fc69910ad0975d0<br>
<br>
URL: <a href="https://github.com/llvm/llvm-project/commit/077bff39d46364035a5dcfa32fc69910ad0975d0" rel="noreferrer" target="_blank">https://github.com/llvm/llvm-project/commit/077bff39d46364035a5dcfa32fc69910ad0975d0</a><br>
DIFF: <a href="https://github.com/llvm/llvm-project/commit/077bff39d46364035a5dcfa32fc69910ad0975d0.diff" rel="noreferrer" target="_blank">https://github.com/llvm/llvm-project/commit/077bff39d46364035a5dcfa32fc69910ad0975d0.diff</a><br>
<br>
LOG: [Analysis] isDereferenceableAndAlignedPointer(): recurse into select's hands<br>
<br>
By doing this within the method itself,<br>
we support traversing multiple levels of selects (TODO: PHI's),<br>
fixing the SROA `std::clamp()` testcase.<br>
<br>
Fixes <a href="https://bugs.llvm.org/show_bug.cgi?id=47271" rel="noreferrer" target="_blank">https://bugs.llvm.org/show_bug.cgi?id=47271</a><br>
Mostly fixes <a href="https://bugs.llvm.org/show_bug.cgi?id=49909" rel="noreferrer" target="_blank">https://bugs.llvm.org/show_bug.cgi?id=49909</a><br>
<br>
Added: <br>
<br>
<br>
Modified: <br>
llvm/lib/Analysis/Loads.cpp<br>
llvm/test/Transforms/SROA/std-clamp.ll<br>
<br>
Removed: <br>
<br>
<br>
<br>
################################################################################<br>
diff --git a/llvm/lib/Analysis/Loads.cpp b/llvm/lib/Analysis/Loads.cpp<br>
index 8d01ea045097..2ae1fd5b5bde 100644<br>
--- a/llvm/lib/Analysis/Loads.cpp<br>
+++ b/llvm/lib/Analysis/Loads.cpp<br>
@@ -59,6 +59,16 @@ static bool isDereferenceableAndAlignedPointer(<br>
// Note that it is not safe to speculate into a malloc'd region because<br>
// malloc may return null.<br>
<br>
+ // Recurse into both hands of select.<br>
+ if (const SelectInst *Sel = dyn_cast<SelectInst>(V)) {<br>
+ return isDereferenceableAndAlignedPointer(Sel->getTrueValue(), Alignment,<br>
+ Size, DL, CtxI, DT, TLI, Visited,<br>
+ MaxDepth) &&<br>
+ isDereferenceableAndAlignedPointer(Sel->getFalseValue(), Alignment,<br>
+ Size, DL, CtxI, DT, TLI, Visited,<br>
+ MaxDepth);<br>
+ }<br>
+<br>
// bitcast instructions are no-ops as far as dereferenceability is concerned.<br>
if (const BitCastOperator *BC = dyn_cast<BitCastOperator>(V)) {<br>
if (BC->getSrcTy()->isPointerTy())<br>
<br>
diff --git a/llvm/test/Transforms/SROA/std-clamp.ll b/llvm/test/Transforms/SROA/std-clamp.ll<br>
index 561904252288..c0132a519722 100644<br>
--- a/llvm/test/Transforms/SROA/std-clamp.ll<br>
+++ b/llvm/test/Transforms/SROA/std-clamp.ll<br>
@@ -6,18 +6,14 @@ target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16<br>
define float @_Z8stdclampfff(float %x, float %lo, float %hi) {<br>
; CHECK-LABEL: @_Z8stdclampfff(<br>
; CHECK-NEXT: bb:<br>
-; CHECK-NEXT: [[I:%.*]] = alloca float, align 4<br>
-; CHECK-NEXT: [[I3:%.*]] = alloca float, align 4<br>
; CHECK-NEXT: [[I4:%.*]] = alloca float, align 4<br>
-; CHECK-NEXT: store float [[X:%.*]], float* [[I]], align 4<br>
-; CHECK-NEXT: store float [[LO:%.*]], float* [[I3]], align 4<br>
; CHECK-NEXT: store float [[HI:%.*]], float* [[I4]], align 4<br>
-; CHECK-NEXT: [[I5:%.*]] = fcmp fast olt float [[X]], [[LO]]<br>
+; CHECK-NEXT: [[I5:%.*]] = fcmp fast olt float [[X:%.*]], [[LO:%.*]]<br>
; CHECK-NEXT: [[I6:%.*]] = fcmp fast olt float [[HI]], [[X]]<br>
-; CHECK-NEXT: [[I7:%.*]] = select i1 [[I6]], float* [[I4]], float* [[I]]<br>
-; CHECK-NEXT: [[I8:%.*]] = select i1 [[I5]], float* [[I3]], float* [[I7]]<br>
-; CHECK-NEXT: [[I9:%.*]] = load float, float* [[I8]], align 4<br>
-; CHECK-NEXT: ret float [[I9]]<br>
+; CHECK-NEXT: [[I9_SROA_SPECULATE_LOAD_FALSE_SROA_SPECULATE_LOAD_TRUE:%.*]] = load float, float* [[I4]], align 4<br>
+; CHECK-NEXT: [[I9_SROA_SPECULATE_LOAD_FALSE_SROA_SPECULATED:%.*]] = select i1 [[I6]], float [[I9_SROA_SPECULATE_LOAD_FALSE_SROA_SPECULATE_LOAD_TRUE]], float [[X]]<br>
+; CHECK-NEXT: [[I9_SROA_SPECULATED:%.*]] = select i1 [[I5]], float [[LO]], float [[I9_SROA_SPECULATE_LOAD_FALSE_SROA_SPECULATED]]<br>
+; CHECK-NEXT: ret float [[I9_SROA_SPECULATED]]<br>
;<br>
bb:<br>
%i = alloca float, align 4<br>
<br>
<br>
<br>
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</blockquote></div>