http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49923
Summary: __attirubte__((packed)) on ARM is sometimes dropped
Product: gcc
Version: 4.6.2
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: c
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: s...@sgh.dk
tst2.c fails with an alignment related problem.
With "static" on line 33 the code generated is this :
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
unsigned int aostk_font_strwidth(const struct aostk_font* font, const char*
str) {
const struct aostk_glyph* g = aostk_get_glyph(font, 0);
return g->advance.x;
0: e5903003 ldr r3, [r0, #3]
}
4: e5d30005 ldrb r0, [r3, #5]
8: e12fff1e bx lr
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
The first ldr-instruction is wrong afaik since struct aostk_font is packed.
Removing "static" fomr line 33 gives this code :
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
const struct aostk_glyph* aostk_get_glyph(const struct aostk_font* f, unsigned
int c) {
return &f->glyphs[0];
0: e5d02004 ldrb r2, [r0, #4]
4: e5d03003 ldrb r3, [r0, #3]
8: e1833402 orr r3, r3, r2, lsl #8
c: e5d02005 ldrb r2, [r0, #5]
10: e5d00006 ldrb r0, [r0, #6]
14: e1833802 orr r3, r3, r2, lsl #16
}
18: e1830c00 orr r0, r3, r0, lsl #24
1c: e12fff1e bx lr
00000020 <aostk_font_strwidth>:
const struct aostk_glyph* glyphs;
};
const struct aostk_glyph* aostk_get_glyph(const struct aostk_font* f, unsigned
int c) {
return &f->glyphs[0];
20: e5d02004 ldrb r2, [r0, #4]
24: e5d03003 ldrb r3, [r0, #3]
28: e1833402 orr r3, r3, r2, lsl #8
2c: e5d02005 ldrb r2, [r0, #5]
30: e1833802 orr r3, r3, r2, lsl #16
34: e5d02006 ldrb r2, [r0, #6]
38: e1833c02 orr r3, r3, r2, lsl #24
unsigned int aostk_font_strwidth(const struct aostk_font* font, const char*
str) {
const struct aostk_glyph* g = aostk_get_glyph(font, 0);
return g->advance.x;
}
3c: e5d30005 ldrb r0, [r3, #5]
40: e12fff1e bx lr
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Notice in aostk_get_glyph that the ldrb-instructions are used instead of ldr.
I compile using -Os, Compiling with -O0 generates correct code. Compiling with
-fno-tree-sra also generates wrong code.
I have bisected the problem and to this commit:
Author: jamborm <jamborm@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Thu Sep 9 23:28:27 2010 +0000
2010-09-10 Martin Jambor <mjam...@suse.cz>
PR tree-optimization/44972
* ipa-prop.c (ipa_modify_call_arguments): Build MEM_REF instead of
calling build_ref_for_offset.
* testsuite/g++.dg/torture/pr34850.C: Remove expected warning.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@164135
138bc75d-0d04-0410-961f-82ee72b054a4
