| Issue |
166356
|
| Summary |
[LoopFusion] Assert "Expecting guard block to have no predecessors"
|
| Labels |
loopoptim,
crash-on-valid
|
| Assignees |
|
| Reporter |
sjoerdmeijer
|
This IR:
```
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32"
target triple = "aarch64-unknown-linux-gnu"
define void @_Z1gb() {
entry:
br i1 false, label %if.else.1, label %for.cond.cleanup13
for.cond.cleanup13: ; preds = %for.cond.cleanup13, %entry
br i1 true, label %for.inc21, label %for.cond.cleanup13
for.inc21: ; preds = %for.cond.cleanup13
br label %if.then.1
if.then.1: ; preds = %for.inc21
br label %if.else.1
if.else.1: ; preds = %if.then.1, %entry
br i1 false, label %if.else.2, label %for.cond.cleanup13.1
for.cond.cleanup13.1: ; preds = %for.cond.cleanup13.1, %if.else.1
br i1 true, label %if.else.2, label %for.cond.cleanup13.1
if.else.2: ; preds = %for.cond.cleanup13.1, %if.else.1
ret void
}
```
triggers this assert:
```
opt: /root/llvm-project/llvm/lib/Transforms/Scalar/LoopFuse.cpp:1945: llvm::Loop* {anonymous}::LoopFuser::fuseGuardedLoops(const {anonymous}::FusionCandidate&, const {anonymous}::FusionCandidate&): Assertion `pred_empty(FC1GuardBlock) && "Expecting guard block to have no predecessors"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace and instructions to reproduce the bug.
Stack dump:
0. Program arguments: /opt/compiler-explorer/clang-assertions-trunk/bin/opt -o /app/output.s -S -S -passes=loop-fusion <source>
1. Running pass "function(loop-fusion)" on module "<source>"
2. Running pass "loop-fusion" on function "_Z1gb"
#0 0x0000000005989ef8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/opt+0x5989ef8)
#1 0x0000000005986da4 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
#2 0x00007f6389e42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
#3 0x00007f6389e969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
#4 0x00007f6389e42476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
#5 0x00007f6389e287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
#6 0x00007f6389e2871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
#7 0x00007f6389e39e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
#8 0x00000000046a310b (anonymous namespace)::LoopFuser::fuseGuardedLoops((anonymous namespace)::FusionCandidate const&, (anonymous namespace)::FusionCandidate const&) LoopFuse.cpp:0:0
#9 0x00000000046a329a (anonymous namespace)::LoopFuser::performFusion((anonymous namespace)::FusionCandidate const&, (anonymous namespace)::FusionCandidate const&) LoopFuse.cpp:0:0
#10 0x00000000046a938e (anonymous namespace)::LoopFuser::fuseCandidates() LoopFuse.cpp:0:0
#11 0x00000000046aaef1 llvm::LoopFusePass::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/opt+0x46aaef1)
```
when compiled with `-S -passes=loop-fusion`, see also: https://godbolt.org/z/v9ddvW1T6
The IR reproducer comes from this C reproducer:
```
int a;
short b;
char c, e, f;
long d;
void g(bool h) {
for (int i; i < 20ULL; i += 4ULL)
if (h)
if (c)
a = f;
else if (e)
for (int j(d); j; j++)
for (int k(f); k; k += 4073709530269)
b = 0;
}
```
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