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* [Bug rtl-optimization/57302] New: Should merge zeroing multiple consecutive memory locations
@ 2013-05-16 15:24 msharov at users dot sourceforge.net
2013-05-17 8:48 ` [Bug rtl-optimization/57302] " rguenth at gcc dot gnu.org
0 siblings, 1 reply; 2+ messages in thread
From: msharov at users dot sourceforge.net @ 2013-05-16 15:24 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57302
Bug ID: 57302
Summary: Should merge zeroing multiple consecutive memory
locations
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: msharov at users dot sourceforge.net
struct A { short a,b; A (void); };
A::A (void) : a(0),b(0) {}
void MoveA (const A* a, A* b) { *b = *a; }
Generates:
_ZN1AC2Ev:
movw $0, (%rdi)
movw $0, 2(%rdi)
ret
_Z5MoveAPK1APS_:
movl (%rdi), %eax
movl %eax, (%rsi)
ret
The optimizer can see that a and b are consecutive in memory and can merge the
memory movs into a single 4-byte mov, but does not do the same for the zeroing
code in the constructor. Merging the zeroing to movl, movq, and mov[au]ps (when
SSE is available), would produce smaller code and fewer memory accesses.
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug rtl-optimization/57302] Should merge zeroing multiple consecutive memory locations
2013-05-16 15:24 [Bug rtl-optimization/57302] New: Should merge zeroing multiple consecutive memory locations msharov at users dot sourceforge.net
@ 2013-05-17 8:48 ` rguenth at gcc dot gnu.org
0 siblings, 0 replies; 2+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-05-17 8:48 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57302
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |DUPLICATE
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
There is a duplicate enhancement bugreport about this.
*** This bug has been marked as a duplicate of bug 23684 ***
^ permalink raw reply [flat|nested] 2+ messages in thread
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2013-05-16 15:24 [Bug rtl-optimization/57302] New: Should merge zeroing multiple consecutive memory locations msharov at users dot sourceforge.net
2013-05-17 8:48 ` [Bug rtl-optimization/57302] " rguenth at gcc dot gnu.org
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