https://bugs.llvm.org/show_bug.cgi?id=51974
Bug ID: 51974
Summary: compiler crash when optimizing multiple _mm_hsub_epi16
intrinsics in certain pattern
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected], [email protected],
[email protected]
Created attachment 25294
--> https://bugs.llvm.org/attachment.cgi?id=25294&action=edit
Compiler output with error log/callstack
I ran into a compiler crash when compiling some SSE code. It appears to stem
from optimizing a specific dataflow for some intrinsics, which causes the DAG
to have cycles. A debug build asserts, while a release build infinitely loops.
The following is a minimal repro example:
#include <immintrin.h>
__m128i do_stuff(__m128i A) {
__m128i B = _mm_hadd_epi16(A, A);
__m128i C = _mm_hadd_epi16(B, A);
return C;
}
when compiled with `clang -O1 -msse4` it exhibits the issue. It also appears to
repro if both intrinsics are changed to one of _mm_hadd_epi32, _mm_hsub_epi16,
or _mm_hsub_epi32. It does not repro with -O0.
I've attached the error output I get from the compiler showing more details
including the state of the DAG and a callstack
I tested this on trunk at commit 9820dd970c1b72c7f77fad647b762053e2f60e31 and
confirmed it's still present. It happens both on Windows and Linux.
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