https://sourceware.org/bugzilla/show_bug.cgi?id=18499
Bug ID: 18499
Summary: LDR immediate not using mov8 and mov.w for Thumb2
Product: binutils
Version: unspecified
Status: NEW
Severity: enhancement
Priority: P2
Component: gas
Assignee: unassigned at sourceware dot org
Reporter: alessandro.marzocchi at gmail dot com
Target Milestone: ---
Created attachment 8346
--> https://sourceware.org/bugzilla/attachment.cgi?id=8346&action=edit
patch
On thumb2 architecture (Cortex M4) the ldr Rx,=imm always translate to a ldr
from literal pool. This patch tries to correctly translate it to a mov8 or a
mov.w/mvn.w when possible. Please double check it as I have never done any
development on GAS source.
test assembly:
.thumb
.arch armv7-m
.syntax unified
.text
ldr r0,=4
ldr r0,=0xFF000000
ldr r0,=0xFFFFFFC0
ldr r0,=0x12345678
pre-patch:
00000000 <.text>:
0: 4801 ldr r0, [pc, #4] ; (8 <.text+0x8>)
2: 4802 ldr r0, [pc, #8] ; (c <.text+0xc>)
4: 4802 ldr r0, [pc, #8] ; (10 <.text+0x10>)
6: 4803 ldr r0, [pc, #12] ; (14 <.text+0x14>)
8: 00000004 .word 0x00000004
c: ff000000 .word 0xff000000
10: ffffffc0 .word 0xffffffc0
14: 12345678 .word 0x12345678
after-patch:
00000000 <.text>:
0: 2004 movs r0, #4
2: f04f 407f mov.w r0, #4278190080 ; 0xff000000
6: f06f 003f mvn.w r0, #63 ; 0x3f
a: 4800 ldr r0, [pc, #0] ; (c <.text+0xc>)
c: 12345678 .word 0x12345678
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