https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88231
Bug ID: 88231
Summary: aligned functions laid down inefficiently
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: minor
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
While testing attribute aligned on functions I noticed that GCC doesn't seem to
take advantage of function alignment to optimize space in the emitted assembly.
For instance, emitting the following functions in the order f8, f1, f2 would
reduce their size overall size from 10 bytes to 3.
$ cat t.c && gcc -Os -c -Wall t.c && objdump -d t.o
__attribute__ ((aligned (1))) void f1 (void) { }
__attribute__ ((aligned (8))) void f8 (void) { }
__attribute__ ((aligned (2))) void f2 (void) { }
t.o: file format elf64-x86-64
Disassembly of section .text:
0000000000000000 <f1>:
0: c3 retq
1: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) ;; wasted space
0000000000000008 <f8>:
8: c3 retq
9: 90 nop ;; wasted space
000000000000000a <f2>:
a: c3 retq
