Compile the attached source code with options -march=armv5te -mthumb -Os
-fno-exceptions, gcc generates:
push {r4, lr}
sub sp, sp, #8
add r4, sp, #4 // redundant
mov r0, r4 // add r0, sp, 4
bl _ZN1XC1Ev
mov r0, r4 // add r0, sp, 4
bl _Z3barP1X
mov r0, r4 // add r0, sp, 4
bl _ZN1XD1Ev
add sp, sp, #8
@ sp needed for prologue
pop {r4, pc}
As mentioned in the comments, the cse is redundant. We can recompute the value
of (sp + 4) each time we want it. With this method we can save one instruction.
--
Summary: unnecessary CSE
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=40615
