https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94381
Bug ID: 94381
Summary: -falign-function/-falign-labels/-falign-loops
documentation is inaccurate
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: driver
Assignee: unassigned at gcc dot gnu.org
Reporter: hjl.tools at gmail dot com
CC: crazylht at gmail dot com, skpgkp2 at gmail dot com
Target Milestone: ---
'-falign-functions'
'-falign-functions=N'
'-falign-functions=N:M'
'-falign-functions=N:M:N2'
'-falign-functions=N:M:N2:M2'
Align the start of functions to the next power-of-two greater than
N, skipping up to M-1 bytes.
But
[hjl@gnu-cfl-2 align]$ cat y.i
void
foo (void)
{
}
[hjl@gnu-cfl-2 align]$ gcc -O2 -S -falign-functions=4 y.i
[hjl@gnu-cfl-2 align]$ cat y.s
.file "y.i"
.text
.p2align 2 <<<<<<<< 4 is not the next power-of-two greater than 4.
.globl foo
.type foo, @function
foo:
.LFB0:
.cfi_startproc
ret
.cfi_endproc
.LFE0:
.size foo, .-foo
.ident "GCC: (GNU) 9.3.1 20200317 (Red Hat 9.3.1-1)"
.section .note.GNU-stack,"",@progbits
[hjl@gnu-cfl-2 align]$
It should be "the next power-of-two no less than N".
'-falign-labels'
'-falign-labels=N'
'-falign-labels=N:M'
'-falign-labels=N:M:N2'
'-falign-labels=N:M:N2:M2'
Align all branch targets to a power-of-two boundary.
and
'-falign-loops'
'-falign-loops=N'
'-falign-loops=N:M'
'-falign-loops=N:M:N2'
'-falign-loops=N:M:N2:M2'
Align loops to a power-of-two boundary.
may leave an impression of alignment is N to the power-of-two.
