http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50329
Sebastian Huber <sebastian.hu...@embedded-brains.de> changed:
What |Removed |Added
----------------------------------------------------------------------------
Attachment #25229|0 |1
is obsolete| |
--- Comment #1 from Sebastian Huber <sebastian.hu...@embedded-brains.de>
2012-07-19 08:11:15 UTC ---
Created attachment 27830
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27830
Sample code
On GCC 4.7.1 20120614 the situation is even more worse:
.file "test.c"
.section ".text"
.align 2
.globl a
.type a, @function
a:
stwu 1,-536(1)
li 9,0
stw 9,8(1)
li 9,-128
stb 9,8(1)
lwz 9,8(1)
addi 1,1,536
stw 9,0(3)
blr
.size a, .-a
.align 2
.globl b
.type b, @function
b:
stwu 1,-544(1)
mflr 0
li 4,0
li 5,516
stw 31,540(1)
mr 31,3
addi 3,1,8
stw 0,548(1)
bl memset
li 9,-128
stb 9,8(1)
lwz 9,8(1)
stw 9,0(31)
lwz 0,548(1)
lwz 31,540(1)
mtlr 0
addi 1,1,544
blr
.size b, .-b
.align 2
.globl c
.type c, @function
c:
li 9,0
li 10,1
rlwimi 9,10,31,0,0
stw 9,0(3)
blr
.size c, .-c
.ident "GCC: (GNU) 4.7.1 20120614 (RTEMS
gcc-4.7.1-3.suse12.1/newlib-1.20.0-10.suse12.1)"
Here we see additional store and load operations to assemble the structure
value.
The test case (c) is also sub-optimal since two instructions are sufficient to
load a 32-bit constant.
