https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86357
Bug ID: 86357
Summary: -falign-{functions,loops,jumps} incorrectly reported
as disabled by -Q --help=optimizers
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: driver
Assignee: unassigned at gcc dot gnu.org
Reporter: sumnon at cj3 dot org
Target Milestone: ---
The options appear to be working correctly, based on the generated code/asm;
they just aren't reported correctly by -Q. -falign-labels appears to be working
and reported correctly.
There are a few related bugs (bug 45996, bug 61588, and bug 43861); they appear
independent/out-of-date but there's a chance fixing them will fix this too.
For example:
$ gcc -Os -Q --help=optimizers | grep align-
-falign-functions [disabled]
-falign-functions= 16
-falign-jumps [disabled]
-falign-jumps= 16
-falign-labels [enabled]
-falign-labels= 0
-falign-loops [disabled]
-falign-loops= 16
$ gcc -O3 -Q --help=optimizers | grep align-
-falign-functions [disabled]
-falign-functions= 16
-falign-jumps [disabled]
-falign-jumps= 16
-falign-labels [enabled]
-falign-labels= 0
-falign-loops [disabled]
-falign-loops= 16
$ gcc -O3 -fno-align-loops -fno-align-functions -Q --help=optimizers | grep
align-
-falign-functions [disabled]
-falign-functions= 1
-falign-jumps [disabled]
-falign-jumps= 16
-falign-labels [enabled]
-falign-labels= 0
-falign-loops [disabled]
-falign-loops= 1
$ gcc -O3 -falign-loops=32 -Q --help=optimizers | grep align-
-falign-functions [disabled]
-falign-functions= 16
-falign-jumps [disabled]
-falign-jumps= 16
-falign-labels [enabled]
-falign-labels= 0
-falign-loops [disabled]
-falign-loops= 32
All of these generate the expected asm, with alignment for -O3 (except when
explicitly turned off) and no alignment for -Os.
gcc -v:
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/8.1.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc/src/gcc/configure --prefix=/usr --libdir=/usr/lib
--libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++ --enable-shared
--enable-threads=posix --enable-libmpx --with-system-zlib --with-isl
--enable-__cxa_atexit --disable-libunwind-exceptions --enable-clocale=gnu
--disable-libstdcxx-pch --disable-libssp --enable-gnu-unique-object
--enable-linker-build-id --enable-lto --enable-plugin
--enable-install-libiberty --with-linker-hash-style=gnu
--enable-gnu-indirect-function --enable-multilib --disable-werror
--enable-checking=release --enable-default-pie --enable-default-ssp
Thread model: posix
gcc version 8.1.1 20180531 (GCC)
