https://bugs.llvm.org/show_bug.cgi?id=50339
Bug ID: 50339
Summary: [Regression] MemorySSA DSE fails to remove redundant
memcpy
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: david.bolvan...@gmail.com
CC: llvm-bugs@lists.llvm.org
extern char a[32];
void f (const void *s)
{
char *p = (char*)__builtin_memcpy (a, s, 16) + 16;
__builtin_memcpy (p - 16, s, 16);
}
Regressed with LLVM 12.
Current IR:
@a = external dso_local local_unnamed_addr global [32 x i8], align 16
define dso_local void @_Z1fPKv(i8* nocapture readonly %0) local_unnamed_addr #0
{
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* nonnull align 16
dereferenceable(16) getelementptr inbounds ([32 x i8], [32 x i8]* @a, i64 0,
i64 0), i8* nonnull align 1 dereferenceable(16) %0, i64 16, i1 false)
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* nonnull align 16
dereferenceable(16) getelementptr inbounds ([32 x i8], [32 x i8]* @a, i64 0,
i64 0), i8* nonnull align 1 dereferenceable(16) %0, i64 16, i1 false)
ret void
}
https://godbolt.org/z/vdTGjdTvn
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