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Handle Top-Level-Regions in polly::isHoistableLoad 

Summary:
This can be seen as a follow-up on my previous differential [D33411](https://reviews.llvm.org/D33411).
We received a bug report where this error was triggered. I have tried my best to recreate the issue in a minimal lit testcase which is also part of this differential.

I only handle return instructions as predecessors to a virtual TLR-exit right now. From inspecting the codebase, it seems `unreachable` instructions may also be of interest here. If requested, I can extend my patches to consider them as well. I would also apply this on `ScopHelper.cpp::isErrorBlock` (see D33411), of course.

Reviewers: philip.pfaffe, bollu

Reviewed By: bollu

Subscribers: Meinersbur, pollydev, llvm-commits

Tags: #polly

Differential Revision: https://reviews.llvm.org/D40492

llvm-svn: 319431
This commit is contained in:
Philip Pfaffe 2017-11-30 13:06:10 +00:00
parent a6bcd53d52
commit 4fe21814d1
2 changed files with 82 additions and 3 deletions
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12
polly/lib/Support/ScopHelper.cpp
View File

@ -473,9 +473,15 @@ bool polly::isHoistableLoad(LoadInst *LInst, Region &R, LoopInfo &LI,
return false;
bool DominatesAllPredecessors = true;
for (auto Pred : predecessors(R.getExit()))
if (R.contains(Pred) && !DT.dominates(&BB, Pred))
DominatesAllPredecessors = false;
if (R.isTopLevelRegion()) {
for (BasicBlock &I : *R.getEntry()->getParent())
if (isa<ReturnInst>(I.getTerminator()) && !DT.dominates(&BB, &I))
DominatesAllPredecessors = false;
} else {
for (auto Pred : predecessors(R.getExit()))
if (R.contains(Pred) && !DT.dominates(&BB, Pred))
DominatesAllPredecessors = false;
}
if (!DominatesAllPredecessors)
continue;

73
polly/test/ScopDetect/tlr_is_hoistable_load.ll Normal file
View File

@ -0,0 +1,73 @@
; RUN: opt %loadPolly -analyze -polly-scops -polly-invariant-load-hoisting \
; RUN: -polly-detect-full-functions < %s | FileCheck %s
;
; This testcase checks for compatibility of the -detect-full-functions
; flag in combination with the -invariant-load-hoisting option. More
; specifically, ScopHelper.cpp::isHoistableLoad only gets called if
; -invariant-load-hoisting is enabled. This function, however, had a bug
; which caused a crash if the region argument was top-level. This test
; is a minimal example that hits this specific code path.
;
; Also note that this file's IR is in no way optimized, i.e. it was
; generated with clang -O0 from the following C-code:
;
; void test() {
; int A[] = {1, 2, 3, 4, 5};
; int len = (sizeof A) / sizeof(int);
; for (int i = 0; i < len; ++i) {
; A[i] = A[i] * 2;
; }
; }
;
; This is also the reason why polly does not detect any scops (the loop
; variable i is loaded from and stored to memory in each iteration):
;
; CHECK: region: 'for.cond => for.end' in function 'test':
; CHECK-NEXT: Invalid Scop!
; CHECK-NEXT: region: 'entry => <Function Return>' in function 'test':
; CHECK-NEXT: Invalid Scop!
;
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
@test.A = private unnamed_addr constant [5 x i32] [i32 1, i32 2, i32 3, i32 4, i32 5], align 16
define void @test() {
entry:
%A = alloca [5 x i32], align 16
%len = alloca i32, align 4
%i = alloca i32, align 4
%0 = bitcast [5 x i32]* %A to i8*
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %0, i8* bitcast ([5 x i32]* @test.A to i8*), i64 20, i32 16, i1 false)
store i32 5, i32* %len, align 4
store i32 0, i32* %i, align 4
br label %for.cond
for.cond: ; preds = %for.inc, %entry
%1 = load i32, i32* %i, align 4
%2 = load i32, i32* %len, align 4
%cmp = icmp slt i32 %1, %2
br i1 %cmp, label %for.body, label %for.end
for.body: ; preds = %for.cond
%3 = load i32, i32* %i, align 4
%idxprom = sext i32 %3 to i64
%arrayidx = getelementptr inbounds [5 x i32], [5 x i32]* %A, i64 0, i64 %idxprom
%4 = load i32, i32* %arrayidx, align 4
%mul = mul nsw i32 %4, 2
%5 = load i32, i32* %i, align 4
%idxprom1 = sext i32 %5 to i64
%arrayidx2 = getelementptr inbounds [5 x i32], [5 x i32]* %A, i64 0, i64 %idxprom1
store i32 %mul, i32* %arrayidx2, align 4
br label %for.inc
for.inc: ; preds = %for.body
%6 = load i32, i32* %i, align 4
%inc = add nsw i32 %6, 1
store i32 %inc, i32* %i, align 4
br label %for.cond
for.end: ; preds = %for.cond
ret void
}
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture writeonly, i8* nocapture readonly, i64, i32, i1)