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[PGO] Early detection regarding whether pgo counter promotion is possible

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Patch by Chris Chrulski

This fixes a problem with the current behavior when assertions are enabled.
A loop that exits to a catchswitch instruction is skipped for the counter
promotion, however this check was being done after the PGOCounterPromoter
tried to collect an insertion point for the exit block. A call to
getFirstInsertionPt() on a block that begins with a catchswitch instruction
triggers an assertion. This change performs a check whether the counter
promotion is possible prior to collecting the ExitBlocks and InsertPts.

Differential Revision: https://reviews.llvm.org/D73222
This commit is contained in:
Andy Kaylor 2020-01-24 09:05:10 -08:00
parent 873a85a605
commit 60e190fa7c
2 changed files with 94 additions and 6 deletions
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27
lib/Transforms/Instrumentation/InstrProfiling.cpp
View File

@ -247,9 +247,14 @@ public:
: LoopToCandidates(LoopToCands), ExitBlocks(), InsertPts(), L(CurLoop),
LI(LI), BFI(BFI) {
// Skip collection of ExitBlocks and InsertPts for loops that will not be
// able to have counters promoted.
SmallVector<BasicBlock *, 8> LoopExitBlocks;
SmallPtrSet<BasicBlock *, 8> BlockSet;
L.getExitBlocks(LoopExitBlocks);
if (!isPromotionPossible(&L, LoopExitBlocks))
return;
for (BasicBlock *ExitBlock : LoopExitBlocks) {
if (BlockSet.insert(ExitBlock).second) {
@ -318,21 +323,31 @@ private:
return true;
}
// Returns the max number of Counter Promotions for LP.
unsigned getMaxNumOfPromotionsInLoop(Loop *LP) {
// Check whether the loop satisfies the basic conditions needed to perform
// Counter Promotions.
bool isPromotionPossible(Loop *LP,
const SmallVectorImpl<BasicBlock *> &LoopExitBlocks) {
// We can't insert into a catchswitch.
SmallVector<BasicBlock *, 8> LoopExitBlocks;
LP->getExitBlocks(LoopExitBlocks);
if (llvm::any_of(LoopExitBlocks, [](BasicBlock *Exit) {
return isa<CatchSwitchInst>(Exit->getTerminator());
}))
return 0;
return false;
if (!LP->hasDedicatedExits())
return 0;
return false;
BasicBlock *PH = LP->getLoopPreheader();
if (!PH)
return false;
return true;
}
// Returns the max number of Counter Promotions for LP.
unsigned getMaxNumOfPromotionsInLoop(Loop *LP) {
SmallVector<BasicBlock *, 8> LoopExitBlocks;
LP->getExitBlocks(LoopExitBlocks);
if (!isPromotionPossible(LP, LoopExitBlocks))
return 0;
SmallVector<BasicBlock *, 8> ExitingBlocks;

73
test/Transforms/PGOProfile/counter_promo_exit_catchswitch.ll Normal file
View File

@ -0,0 +1,73 @@
; Test that instrumentation counter promotion for loops does not fail during
; compilation for loops that exit to a catchswitch block. In this case, counters
; do not get promoted out of the loop body.
; RUN: opt < %s -pgo-instr-gen -instrprof -do-counter-promotion=true -S | FileCheck %s
; RUN: opt < %s -passes=pgo-instr-gen,instrprof -do-counter-promotion=true -S | FileCheck %s
; Source used to create test:
;
; extern void may_throw(int);
; char buffer[200];
; void run(int count) {
; try {
; for (int i = 0; i < count; ++i) {
; if (buffer[i] == 0)
; break;
; may_throw(i);
; }
; }
; catch (...) {
; throw;
; }
;}
%eh.ThrowInfo = type { i32, i32, i32, i32 }
@"?buffer@@3PADA" = dso_local local_unnamed_addr global [200 x i8] zeroinitializer, align 16
define dso_local void @"?run@@YAXH@Z"(i32 %count) local_unnamed_addr personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) {
entry:
br label %for.cond
for.cond: ; preds = %for.inc, %entry
%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
%cmp = icmp slt i32 %i.0, %count
br i1 %cmp, label %for.body, label %cleanup
for.body: ; preds = %for.cond
; CHECK: for.body:
; CHECK: %pgocount1 = load i64, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @"__profc_?run@@YAXH@Z", i64 0, i64 0)
; CHECK: %1 = add i64 %pgocount1, 1
; CHECK: store i64 %1, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @"__profc_?run@@YAXH@Z", i64 0, i64 0)
%idxprom = zext i32 %i.0 to i64
%arrayidx = getelementptr inbounds [200 x i8], [200 x i8]* @"?buffer@@3PADA", i64 0, i64 %idxprom
%0 = load i8, i8* %arrayidx, align 1
%cmp1 = icmp eq i8 %0, 0
br i1 %cmp1, label %cleanup, label %if.end
if.end: ; preds = %for.body
invoke void @"?may_throw@@YAXH@Z"(i32 %i.0)
to label %for.inc unwind label %catch.dispatch
for.inc: ; preds = %if.end
; CHECK: for.inc:
; CHECK: %pgocount2 = load i64, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @"__profc_?run@@YAXH@Z", i64 0, i64 1)
; CHECK: %3 = add i64 %pgocount2, 1
; CHECK: store i64 %3, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @"__profc_?run@@YAXH@Z", i64 0, i64 1)
%inc = add nuw nsw i32 %i.0, 1
br label %for.cond
cleanup: ; preds = %for.body, %for.cond
ret void
catch.dispatch: ; preds = %if.end
%1 = catchswitch within none [label %catch] unwind to caller
catch: ; preds = %catch.dispatch
%2 = catchpad within %1 [i8* null, i32 64, i8* null]
call void @_CxxThrowException(i8* null, %eh.ThrowInfo* null) #2 [ "funclet"(token %2) ]
unreachable
}
declare dso_local void @"?may_throw@@YAXH@Z"(i32)
declare dso_local void @_CxxThrowException(i8*, %eh.ThrowInfo*)
declare dso_local i32 @__CxxFrameHandler3(...)