https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90883
Jeffrey A. Law <law at redhat dot com> changed:
What |Removed |Added
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CC| |law at redhat dot com
--- Comment #6 from Jeffrey A. Law <law at redhat dot com> ---
So we could have DSE ignore the padding bytes at the read point. We may have
even discussed that at some point. That results in something like this from
the gimple optimizers:
slow ()
{
struct C D.25898;
struct C D.29462;
;; basic block 2, loop depth 0, count 1073741824 (estimated locally), maybe
hot
;; prev block 0, next block 1, flags: (NEW, REACHABLE, VISITED)
;; pred: ENTRY [always] count:1073741824 (estimated locally)
(FALLTHRU,EXECUTABLE)
MEM <char[4]> [(struct C *)&D.25898 + 8B] = {};
D.25898.a = {};
D.29462 = D.25898;
D.25898 ={v} {CLOBBER};
return D.29462;
;; succ: EXIT [always] count:1073741824 (estimated locally)
}
But that still doesn't really help. Even if we tell DSE stores to the bytes
for C.b aren't live (they're uninitialized), then we get something like this:
slow ()
{
struct C D.25898;
struct C D.29462;
;; basic block 2, loop depth 0, count 1073741824 (estimated locally), maybe
hot
;; prev block 0, next block 1, flags: (NEW, REACHABLE, VISITED)
;; pred: ENTRY [always] count:1073741824 (estimated locally)
(FALLTHRU,EXECUTABLE)
D.25898.a = {};
D.29462 = D.25898;
D.25898 ={v} {CLOBBER};
return D.29462;
;; succ: EXIT [always] count:1073741824 (estimated locally)
}
WHich still isn't sufficient to get good code.
I'm not really sure what you want DSE to do here Richi :-)
