Compile the attached test case with options -Os, I can get the ideal result:
foo:
cmp r0, #0
ldr r3, .L5
movne r2, #10
moveq r2, #20
str r2, [r3, #0]
bx lr
But when I changed the options to -O2, I got:
foo:
cmp r0, #0
ldrne r3, .L4 // A
ldreq r3, .L4 // B
movne r2, #10
moveq r2, #20
strne r2, [r3, #0] // C
streq r2, [r3, #0] // D
bx lr
Instructions A/B/C/D should not executed conditionally since they do the same
thing in either case.
Similarly when I changed to options to -Os -fpic, I got:
foo:
ldr r3, .L5
ldr r2, .L5+4
.LPIC0:
add r3, pc, r3
cmp r0, #0
ldrne r3, [r3, r2] // E
ldreq r3, [r3, r2] // F
movne r2, #10
moveq r2, #20
str r2, [r3, #0]
bx lr
Instructions E/F should not execute conditionally.
--
Summary: wrong if conversion optimization
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: carrot at google dot com
GCC build triplet: i686-linux
GCC host triplet: i686-linux
GCC target triplet: arm-eabi
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42496
