https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115332
Bug ID: 115332
Summary: Using label-as-value in asm statement removes label
Product: gcc
Version: 13.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: mr.bossman075 at gmail dot com
Target Milestone: ---
$ riscv64-unknown-elf-gcc -v
Using built-in specs.
COLLECT_GCC=riscv64-unknown-elf-gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/riscv64-unknown-elf/13.2.0/lto-wrapper
Target: riscv64-unknown-elf
Configured with: ../gcc-13.2.0/configure --build=x86_64-linux-gnu --prefix=/usr
--includedir='/usr/lib/include' --mandir='/usr/lib/share/man'
--infodir='/usr/lib/share/info' --sysconfdir=/etc --localstatedir=/var
--disable-option-checking --disable-silent-rules
--libdir='/usr/lib/lib/x86_64-linux-gnu'
--libexecdir='/usr/lib/lib/x86_64-linux-gnu' --disable-maintainer-mode
--disable-dependency-tracking --enable-languages=c,c++ --prefix=/usr/lib
--infodir=/usr/share/doc/gcc-riscv64-unknown-elf/info --mandir=/usr/share/man
--htmldir=/usr/share/doc/gcc-riscv64-unknown-elf/html
--pdfdir=/usr/share/doc/gcc-riscv64-unknown-elf/pdf --bindir=/usr/bin
--libexecdir=/usr/lib --libdir=/usr/lib --with-system-zlib --enable-multilib
--disable-decimal-float --disable-libffi --disable-libgomp --disable-libmudflap
--disable-libquadmath --disable-libssp --disable-libstdcxx-pch
--disable-libstdc++-v3 --disable-nls --disable-shared --disable-threads
--with-arch=rv64imafdc --enable-tls --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=riscv64-unknown-elf --with-gnu-as
--with-gnu-ld --with-headers=no --without-newlib --with-pkgversion=13.2.0-10+12
--without-included-gettext SED=/bin/sed SHELL=/bin/sh BASH=/bin/bash
CONFIG_SHELL=/bin/bash AR_FOR_TARGET=riscv64-unknown-elf-ar
AS_FOR_TARGET=riscv64-unknown-elf-as LD_FOR_TARGET=riscv64-unknown-elf-ld
NM_FOR_TARGET=riscv64-unknown-elf-nm
OBJDUMP_FOR_TARGET=riscv64-unknown-elf-objdump
RANLIB_FOR_TARGET=riscv64-unknown-elf-ranlib
READELF_FOR_TARGET=riscv64-unknown-elf-readelf
STRIP_FOR_TARGET=riscv64-unknown-elf-strip ASFLAGS= ASFLAGS_FOR_BUILD=
CFLAGS='-g -O2
-ffile-prefix-map=/build/reproducible-path/gcc-riscv64-unknown-elf-12=.
-fstack-protector-strong -fstack-clash-protection -fcf-protection'
'CFLAGS_FOR_BUILD=-g -O2' CPPFLAGS='-Wdate-time -D_FORTIFY_SOURCE=2'
CPPFLAGS_FOR_BUILD= CXXFLAGS='-g -O2
-ffile-prefix-map=/build/reproducible-path/gcc-riscv64-unknown-elf-12=.
-fstack-protector-strong -fstack-clash-protection -fcf-protection'
'CXXFLAGS_FOR_BUILD=-g -O2' DFLAGS=-frelease DFLAGS_FOR_BUILD=-frelease
FCFLAGS='-g -O2
-ffile-prefix-map=/build/reproducible-path/gcc-riscv64-unknown-elf-12=.
-fstack-protector-strong -fstack-clash-protection -fcf-protection'
'FCFLAGS_FOR_BUILD=-g -O2' FFLAGS='-g -O2
-ffile-prefix-map=/build/reproducible-path/gcc-riscv64-unknown-elf-12=.
-fstack-protector-strong -fstack-clash-protection -fcf-protection'
'FFLAGS_FOR_BUILD=-g -O2' LDFLAGS='-Wl,-z,relro -Wl,-z,now' LDFLAGS_FOR_BUILD=
OBJCFLAGS='-g -O2
-ffile-prefix-map=/build/reproducible-path/gcc-riscv64-unknown-elf-12=.
-fstack-protector-strong -fstack-clash-protection -fcf-protection'
'OBJCFLAGS_FOR_BUILD=-g -O2' OBJCXXFLAGS='-g -O2
-ffile-prefix-map=/build/reproducible-path/gcc-riscv64-unknown-elf-12=.
-fstack-protector-strong -fstack-clash-protection -fcf-protection'
'OBJCXXFLAGS_FOR_BUILD=-g -O2' INHIBIT_LIBC_CFLAGS=-DUSE_TM_CLONE_REGISTRY=0
'CFLAGS_FOR_TARGET=-Os -mcmodel=medany' 'CXXFLAGS_FOR_TARGET=-Os
-mcmodel=medany'
Thread model: single
Supported LTO compression algorithms: zlib
gcc version 13.2.0 (13.2.0-10+12)
int test_labels()
{
void *label = &&l;
long val;
asm volatile("mv %0, %1"
: "=r" (val) : "r" (label)
: "memory");
return 1;
l:
return 0;
}
int test_labels2()
{
void *label = &&l;
long val;
asm volatile goto("mv %0, %1"
: "=r" (val) : "r" (label)
: "memory": l);
return 1;
l:
return 0;
}
In the above code in `test_labels` the label `l` will be removed even though we
are using the "label as value" in the asm statement. The second test uses asm
goto to tell the compiler that the label is used. The compilation output is
what would be expected of the first. The above code was compiled with the
command below. This doesn't appear to be architecture-dependent, but was
originally found on riscv.
riscv64-unknown-elf-gcc -S -c -O1 -Wall -Wextra -fno-strict-aliasing -fwrapv
test.c -o-
The output of the above command is:
.file "test.c"
.option nopic
.attribute arch, "rv64i2p1_m2p0_a2p1_f2p2_d2p2_c2p0_zicsr2p0"
.attribute unaligned_access, 0
.attribute stack_align, 16
.text
.align 1
.globl test_labels
.type test_labels, @function
test_labels:
.L2:
lui a5,%hi(.L2)
addi a5,a5,%lo(.L2)
### Note here that .L2 is the same as test_labels
#APP
# 6 "test.c" 1
mov a5, a5
# 0 "" 2
#NO_APP
li a0,1
ret
.size test_labels, .-test_labels
.align 1
.globl test_labels2
.type test_labels2, @function
test_labels2:
lui a5,%hi(.L4)
addi a5,a5,%lo(.L4)
#APP
# 20 "test.c" 1
mov a5, a5
# 0 "" 2
#NO_APP
li a0,1
ret
.L5:
li a0,0
.L4:
ret
.size test_labels2, .-test_labels2
.ident "GCC: (13.2.0-10+12) 13.2.0"
Here is another example using arm:
https://godbolt.org/z/cqEzPvrGx
I'm not entirely sure if this is a duplicate of Bug 44298, but the premise is
slightly different so I'll ask anyway.
Even if this isn't a bug, which is understandable, why doesn't it generate a
warning that the label was moved?
