<div dir="ltr">Ah, sorry - I think I tested that first & found it was used. I forget what the particular use was - but should be easy to reproduce & hopefully there's some good fix for it. Happy to help with the implementation or ideas about how to address it if you like.</div><br><div class="gmail_quote"><div dir="ltr">On Thu, Mar 29, 2018 at 10:15 AM Philip Reames <<a href="mailto:listmail@philipreames.com">listmail@philipreames.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div text="#000000" bgcolor="#FFFFFF">
<p><br>
</p>
<br>
<div class="m_-6492984690386630205moz-cite-prefix">On 03/28/2018 04:16 PM, David Blaikie
wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr"><br>
<br>
<div class="gmail_quote">
<div dir="ltr">On Tue, Mar 20, 2018 at 10:11 AM Philip Reames
via llvm-commits <<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.org</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author:
reames<br>
Date: Tue Mar 20 10:09:21 2018<br>
New Revision: 328004<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=328004&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project?rev=328004&view=rev</a><br>
Log:<br>
Add an analysis printer for must execute reasoning<br>
<br>
Many of our loop passes make use of so called "must execute"
or "guaranteed to execute" facts to prove the legality of
code motion. The basic notion is that we know (by
assumption) an instruction didn't fault at it's original
location, so if the location we move it to is strictly post
dominated by the original, then we can't have introduced a
new fault.<br>
<br>
At the moment, the testing for this logic is somewhat adhoc
and done mostly through LICM. Since I'm working on that
code, I want to improve the testing. This patch is the first
step in that direction. It doesn't actually test the variant
used by the loop passes - I need to move that to the
Analysis library first - but instead exercises an alternate
implementation used by SCEV. (I plan on merging both
implementations.)<br>
<br>
Note: I'll be replacing the printing logic within this with
an annotation based version in the near future. Anna
suggested this in review, and it seems like a strictly
better format.<br>
<br>
Differential Revision: <a href="https://reviews.llvm.org/D44524" rel="noreferrer" target="_blank">https://reviews.llvm.org/D44524</a><br>
<br>
<br>
Added:<br>
llvm/trunk/lib/Analysis/MustExecute.cpp<br>
llvm/trunk/test/Analysis/MustExecute/<br>
llvm/trunk/test/Analysis/MustExecute/loop-header.ll<br>
Modified:<br>
llvm/trunk/include/llvm/Analysis/Passes.h<br>
llvm/trunk/include/llvm/InitializePasses.h<br>
llvm/trunk/include/llvm/LinkAllPasses.h<br>
llvm/trunk/lib/Analysis/Analysis.cpp<br>
llvm/trunk/lib/Analysis/CMakeLists.txt<br>
<br>
Modified: llvm/trunk/include/llvm/Analysis/Passes.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/Passes.h?rev=328004&r1=328003&r2=328004&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/Passes.h?rev=328004&r1=328003&r2=328004&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/include/llvm/Analysis/Passes.h (original)<br>
+++ llvm/trunk/include/llvm/Analysis/Passes.h Tue Mar 20
10:09:21 2018<br>
@@ -96,6 +96,14 @@ namespace llvm {<br>
//<br>
FunctionPass *createMemDerefPrinter();<br>
<br>
+
//===--------------------------------------------------------------------===//<br>
+ //<br>
+ // createMustExecutePrinter - This pass collects
information about which<br>
+ // instructions within a loop are guaranteed to execute
if the loop header is<br>
+ // entered and prints it with -analyze.<br>
+ //<br>
+ FunctionPass *createMustExecutePrinter();<br>
+<br>
}<br>
<br>
#endif<br>
<br>
Modified: llvm/trunk/include/llvm/InitializePasses.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/InitializePasses.h?rev=328004&r1=328003&r2=328004&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/InitializePasses.h?rev=328004&r1=328003&r2=328004&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/include/llvm/InitializePasses.h (original)<br>
+++ llvm/trunk/include/llvm/InitializePasses.h Tue Mar 20
10:09:21 2018<br>
@@ -268,6 +268,7 @@ void initializeMergedLoadStoreMotionLega<br>
void initializeMetaRenamerPass(PassRegistry&);<br>
void
initializeModuleDebugInfoPrinterPass(PassRegistry&);<br>
void
initializeModuleSummaryIndexWrapperPassPass(PassRegistry&);<br>
+void initializeMustExecutePrinterPass(PassRegistry&);<br>
void
initializeNameAnonGlobalLegacyPassPass(PassRegistry&);<br>
void
initializeNaryReassociateLegacyPassPass(PassRegistry&);<br>
void initializeNewGVNLegacyPassPass(PassRegistry&);<br>
<br>
Modified: llvm/trunk/include/llvm/LinkAllPasses.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/LinkAllPasses.h?rev=328004&r1=328003&r2=328004&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/LinkAllPasses.h?rev=328004&r1=328003&r2=328004&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/include/llvm/LinkAllPasses.h (original)<br>
+++ llvm/trunk/include/llvm/LinkAllPasses.h Tue Mar 20
10:09:21 2018<br>
@@ -207,6 +207,7 @@ namespace {<br>
(void) llvm::createRewriteSymbolsPass();<br>
(void) llvm::createStraightLineStrengthReducePass();<br>
(void) llvm::createMemDerefPrinter();<br>
+ (void) llvm::createMustExecutePrinter();<br>
(void) llvm::createFloat2IntPass();<br>
(void)
llvm::createEliminateAvailableExternallyPass();<br>
(void) llvm::createScalarizeMaskedMemIntrinPass();<br>
<br>
Modified: llvm/trunk/lib/Analysis/Analysis.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/Analysis.cpp?rev=328004&r1=328003&r2=328004&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/Analysis.cpp?rev=328004&r1=328003&r2=328004&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/Analysis/Analysis.cpp (original)<br>
+++ llvm/trunk/lib/Analysis/Analysis.cpp Tue Mar 20 10:09:21
2018<br>
@@ -65,6 +65,7 @@ void llvm::initializeAnalysis(PassRegist<br>
initializeMemoryDependenceWrapperPassPass(Registry);<br>
initializeModuleDebugInfoPrinterPass(Registry);<br>
initializeModuleSummaryIndexWrapperPassPass(Registry);<br>
+ initializeMustExecutePrinterPass(Registry);<br>
initializeObjCARCAAWrapperPassPass(Registry);<br>
initializeOptimizationRemarkEmitterWrapperPassPass(Registry);<br>
initializePostDominatorTreeWrapperPassPass(Registry);<br>
<br>
Modified: llvm/trunk/lib/Analysis/CMakeLists.txt<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/CMakeLists.txt?rev=328004&r1=328003&r2=328004&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/CMakeLists.txt?rev=328004&r1=328003&r2=328004&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/Analysis/CMakeLists.txt (original)<br>
+++ llvm/trunk/lib/Analysis/CMakeLists.txt Tue Mar 20
10:09:21 2018<br>
@@ -58,6 +58,7 @@ add_llvm_library(LLVMAnalysis<br>
MemorySSAUpdater.cpp<br>
ModuleDebugInfoPrinter.cpp<br>
ModuleSummaryAnalysis.cpp<br>
+ MustExecute.cpp<br>
ObjCARCAliasAnalysis.cpp<br>
ObjCARCAnalysisUtils.cpp<br>
ObjCARCInstKind.cpp<br>
<br>
Added: llvm/trunk/lib/Analysis/MustExecute.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/MustExecute.cpp?rev=328004&view=auto" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/MustExecute.cpp?rev=328004&view=auto</a><br>
==============================================================================<br>
--- llvm/trunk/lib/Analysis/MustExecute.cpp (added)<br>
+++ llvm/trunk/lib/Analysis/MustExecute.cpp Tue Mar 20
10:09:21 2018<br>
@@ -0,0 +1,102 @@<br>
+//===- MustExecute.cpp - Printer for isGuaranteedToExecute
----------------===//<br>
+//<br>
+// The LLVM Compiler Infrastructure<br>
+//<br>
+// This file is distributed under the University of
Illinois Open Source<br>
+// License. See LICENSE.TXT for details.<br>
+//<br>
+//===----------------------------------------------------------------------===//<br>
+<br>
+#include "llvm/Analysis/LoopInfo.h"<br>
+#include "llvm/Analysis/Passes.h"<br>
+#include "llvm/Analysis/ValueTracking.h"<br>
+#include "llvm/IR/DataLayout.h"<br>
+#include "llvm/IR/InstIterator.h"<br>
+#include "llvm/IR/LLVMContext.h"<br>
+#include "llvm/IR/Module.h"<br>
+#include "llvm/Support/ErrorHandling.h"<br>
+#include "llvm/Support/raw_ostream.h"<br>
+#include "llvm/Transforms/Utils/LoopUtils.h"<br>
</blockquote>
<div><br>
This looks like a circular/invalid dependency? Transforms
depend on Analysis, not the other way around?<br>
<br>
Would be great to get this fixed - happy to help, if you've
some ideas.<br>
<br>
Moving the whole LoopUtils isn't immediately possible, its
implementation depends on BasicBlockUtils. (& also many
of these utilities seem more for mutation, which isn't
relevant to Analysis - so maybe it needs to be split up?)<br>
</div>
</div>
</div>
</blockquote></div><div text="#000000" bgcolor="#FFFFFF">
I think this is just a stale header include. I'm building to
confirm now and if so will remove it. <br></div><div text="#000000" bgcolor="#FFFFFF">
<blockquote type="cite">
<div dir="ltr">
<div class="gmail_quote">
<div> </div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
+using namespace llvm;<br>
+<br>
+namespace {<br>
+ struct MustExecutePrinter : public FunctionPass {<br>
+ DenseMap<Value*, SmallVector<Loop*, 4> >
MustExec;<br>
+ SmallVector<Value *, 4> Ordering;<br>
+<br>
+ static char ID; // Pass identification, replacement for
typeid<br>
+ MustExecutePrinter() : FunctionPass(ID) {<br>
+
initializeMustExecutePrinterPass(*PassRegistry::getPassRegistry());<br>
+ }<br>
+ void getAnalysisUsage(AnalysisUsage &AU) const
override {<br>
+ AU.setPreservesAll();<br>
+ AU.addRequired<DominatorTreeWrapperPass>();<br>
+ AU.addRequired<LoopInfoWrapperPass>();<br>
+ }<br>
+ bool runOnFunction(Function &F) override;<br>
+ void print(raw_ostream &OS, const Module * =
nullptr) const override;<br>
+ void releaseMemory() override {<br>
+ MustExec.clear();<br>
+ Ordering.clear();<br>
+ }<br>
+ };<br>
+}<br>
+<br>
+char MustExecutePrinter::ID = 0;<br>
+INITIALIZE_PASS_BEGIN(MustExecutePrinter,
"print-mustexecute",<br>
+ "Instructions which execute on loop
entry", false, true)<br>
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)<br>
+INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)<br>
+INITIALIZE_PASS_END(MustExecutePrinter,
"print-mustexecute",<br>
+ "Instructions which execute on loop
entry", false, true)<br>
+<br>
+FunctionPass *llvm::createMustExecutePrinter() {<br>
+ return new MustExecutePrinter();<br>
+}<br>
+<br>
+bool isMustExecuteIn(Instruction &I, Loop *L,
DominatorTree *DT) {<br>
+ // TODO: move loop specific code to analysis<br>
+ //LoopSafetyInfo LSI;<br>
+ //computeLoopSafetyInfo(&LSI, L);<br>
+ //return isGuaranteedToExecute(I, DT, L, &LSI);<br>
+ return isGuaranteedToExecuteForEveryIteration(&I, L);<br>
+}<br>
+<br>
+bool MustExecutePrinter::runOnFunction(Function &F) {<br>
+ auto &LI =
getAnalysis<LoopInfoWrapperPass>().getLoopInfo();<br>
+ auto &DT =
getAnalysis<DominatorTreeWrapperPass>().getDomTree();<br>
+ for (auto &I: instructions(F)) {<br>
+ Loop *L = LI.getLoopFor(I.getParent());<br>
+ while (L) {<br>
+ if (isMustExecuteIn(I, L, &DT)) {<br>
+ if (!MustExec.count(&I))<br>
+ Ordering.push_back(&I);<br>
+ MustExec[&I].push_back(L);<br>
+ }<br>
+ L = L->getParentLoop();<br>
+ };<br>
+ }<br>
+ return false;<br>
+}<br>
+<br>
+void MustExecutePrinter::print(raw_ostream &OS, const
Module *M) const {<br>
+ OS << "The following are guaranteed to execute (for
the respective loops):\n";<br>
+ for (Value *V: Ordering) {<br>
+ V->printAsOperand(OS);<br>
+ auto NumLoops = MustExec.lookup(V).size();<br>
+ if (NumLoops > 1)<br>
+ OS << "\t(mustexec in " << NumLoops
<< " loops: ";<br>
+ else<br>
+ OS << "\t(mustexec in: ";<br>
+<br>
+ bool first = true;<br>
+ for (const Loop *L : MustExec.lookup(V)) {<br>
+ if (!first)<br>
+ OS << ", ";<br>
+ first = false;<br>
+ OS << L->getHeader()->getName();<br>
+ }<br>
+ OS << ")\n";<br>
+ }<br>
+ OS << "\n";<br>
+}<br>
<br>
Added: llvm/trunk/test/Analysis/MustExecute/loop-header.ll<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/MustExecute/loop-header.ll?rev=328004&view=auto" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/MustExecute/loop-header.ll?rev=328004&view=auto</a><br>
==============================================================================<br>
--- llvm/trunk/test/Analysis/MustExecute/loop-header.ll
(added)<br>
+++ llvm/trunk/test/Analysis/MustExecute/loop-header.ll Tue
Mar 20 10:09:21 2018<br>
@@ -0,0 +1,80 @@<br>
+; RUN: opt -analyze -print-mustexecute %s<br>
+<br>
+; CHECK: Printing analysis 'Instructions which execute on
loop entry' for function 'header_with_icf':<br>
+; CHECK: The following are guaranteed to execute (for the
respective loops):<br>
+; CHECK: %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop
] (mustexec in: loop)<br>
+; CHECK: %v = load i32, i32* %p (mustexec in: loop)<br>
+; CHECK: call void @maythrow_and_use(i32 %v) (mustexec
in: loop)<br>
+; CHECK-NOT: add<br>
+define i1 @header_with_icf(i32* noalias %p, i32 %high) {<br>
+entry:<br>
+ br label %loop<br>
+<br>
+loop:<br>
+ %iv = phi i32 [0, %entry], [%iv.next, %loop]<br>
+ %v = load i32, i32* %p<br>
+ call void @maythrow_and_use(i32 %v)<br>
+ %iv.next = add nsw nuw i32 %iv, 1<br>
+ %exit.test = icmp slt i32 %iv, %high<br>
+ br i1 %exit.test, label %exit, label %loop<br>
+<br>
+exit:<br>
+ ret i1 false<br>
+}<br>
+<br>
+; CHECK: Printing analysis 'Instructions which execute on
loop entry' for function 'test':<br>
+; CHECK: The following are guaranteed to execute (for the
respective loops):<br>
+; CHECK: %iv = phi i32 [ 0, %entry ], [ %iv.next, %next
] (mustexec in: loop)<br>
+; CHECK: %v = load i32, i32* %p (mustexec in: loop)<br>
+; CHECK: br label %next (mustexec in: loop)<br>
+define i1 @test(i32* noalias %p, i32 %high) {<br>
+entry:<br>
+ br label %loop<br>
+<br>
+loop:<br>
+ %iv = phi i32 [0, %entry], [%iv.next, %next]<br>
+ %v = load i32, i32* %p<br>
+ br label %next<br>
+next:<br>
+ call void @maythrow_and_use(i32 %v)<br>
+ %iv.next = add nsw nuw i32 %iv, 1<br>
+ %exit.test = icmp slt i32 %iv, %high<br>
+ br i1 %exit.test, label %exit, label %loop<br>
+<br>
+exit:<br>
+ ret i1 false<br>
+}<br>
+<br>
+; CHECK: Printing analysis 'Instructions which execute on
loop entry' for function 'nested':<br>
+; CHECK: The following are guaranteed to execute (for the
respective loops):<br>
+; CHECK: %iv = phi i32 [ 0, %entry ], [ %iv.next, %next
] (mustexec in: loop)<br>
+; CHECK: br label %inner_loop (mustexec in: loop)<br>
+; FIXME: These three are also must execute for the outer
loop.<br>
+; CHECK: %v = load i32, i32* %p (mustexec in:
inner_loop)<br>
+; CHECK: %inner.test = icmp eq i32 %v, 0 (mustexec
in: inner_loop)<br>
+; CHECK: br i1 %inner.test, label %inner_loop, label
%next (mustexec in: inner_loop)<br>
+define i1 @nested(i32* noalias %p, i32 %high) {<br>
+entry:<br>
+ br label %loop<br>
+<br>
+loop:<br>
+ %iv = phi i32 [0, %entry], [%iv.next, %next]<br>
+ br label %inner_loop<br>
+<br>
+inner_loop:<br>
+ %v = load i32, i32* %p<br>
+ %inner.test = icmp eq i32 %v, 0<br>
+ br i1 %inner.test, label %inner_loop, label %next<br>
+<br>
+next:<br>
+ call void @maythrow_and_use(i32 %v)<br>
+ %iv.next = add nsw nuw i32 %iv, 1<br>
+ %exit.test = icmp slt i32 %iv, %high<br>
+ br i1 %exit.test, label %exit, label %loop<br>
+<br>
+exit:<br>
+ ret i1 false<br>
+}<br>
+<br>
+<br>
+declare void @maythrow_and_use(i32)<br>
<br>
<br>
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</blockquote>
</div>
</div>
</blockquote>
<br>
</div></blockquote></div>