public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug tree-optimization/103674] New: Poor codegen for C++ casts
@ 2021-12-12 20:10 hubicka at gcc dot gnu.org
2021-12-13 11:05 ` [Bug tree-optimization/103674] " hubicka at gcc dot gnu.org
0 siblings, 1 reply; 2+ messages in thread
From: hubicka at gcc dot gnu.org @ 2021-12-12 20:10 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103674
Bug ID: 103674
Summary: Poor codegen for C++ casts
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: hubicka at gcc dot gnu.org
Target Milestone: ---
Compiling:
struct a {int a;};
struct b {int b;};
struct c : a, b {};
int
test(struct c *c)
{
struct b *b=c;
return b->b;
}
with -O2 leads to:
.text
.LHOTB0:
.p2align 4
.globl _Z4testP1c
.type _Z4testP1c, @function
_Z4testP1c:
.LFB0:
.cfi_startproc
testq %rdi, %rdi
je .L2
movl 4(%rdi), %eax
ret
.cfi_endproc
.section .text.unlikely
.cfi_startproc
.type _Z4testP1c.cold, @function
_Z4testP1c.cold:
.LFSB0:
.L2:
movl 0, %eax
ud2
.cfi_endproc
.LFE0:
while clang does:
_Z4testP1c: # @_Z4testP1c
.cfi_startproc
# %bb.0:
leaq 4(%rdi), %rax
testq %rdi, %rdi
cmoveq %rdi, %rax
movl (%rax), %eax
retq
And so does gcc 4.8.5:
test(c*):
leaq 4(%rdi), %rdx
xorl %eax, %eax
testq %rdi, %rdi
cmovne %rdx, %rax
movl (%rax), %eax
ret
So this is technically a regression.
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug tree-optimization/103674] Poor codegen for C++ casts
2021-12-12 20:10 [Bug tree-optimization/103674] New: Poor codegen for C++ casts hubicka at gcc dot gnu.org
@ 2021-12-13 11:05 ` hubicka at gcc dot gnu.org
0 siblings, 0 replies; 2+ messages in thread
From: hubicka at gcc dot gnu.org @ 2021-12-13 11:05 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103674
Jan Hubicka <hubicka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |DUPLICATE
--- Comment #1 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
Actually this looks like yet another full duplicate of PR95663
*** This bug has been marked as a duplicate of bug 95663 ***
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2021-12-13 11:05 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-12-12 20:10 [Bug tree-optimization/103674] New: Poor codegen for C++ casts hubicka at gcc dot gnu.org
2021-12-13 11:05 ` [Bug tree-optimization/103674] " hubicka at gcc dot gnu.org
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).