https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89435
Bug ID: 89435
Summary: wrong code with -O1 -march=armv4
-fno-forward-propagate with __builtin_sub_overflow()
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: zsojka at seznam dot cz
Target Milestone: ---
Host: x86_64-pc-linux-gnu
Target: armv7a-hardfloat-linux-gnueabi
Created attachment 45785
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=45785&action=edit
reduced testcase
Output:
$ armv7a-hardfloat-linux-gnueabi-gcc -O1 -march=armv4 -fno-forward-propagate
testcase.c -static
$ ./a.out
qemu: uncaught target signal 6 (Aborted) - core dumped
Aborted
$ armv7a-hardfloat-linux-gnueabi-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-armv7a-hardfloat/bin/armv7a-hardfloat-linux-gnueabi-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-269006-checking-yes-rtl-df-extra-armv7a-hardfloat/bin/../libexec/gcc/armv7a-hardfloat-linux-gnueabi/9.0.1/lto-wrapper
Target: armv7a-hardfloat-linux-gnueabi
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--with-cloog --with-ppl --with-isl --with-float=hard --with-fpu=vfpv4
--with-arch=armv7-a --with-sysroot=/usr/armv7a-hardfloat-linux-gnueabi
--build=x86_64-pc-linux-gnu --host=x86_64-pc-linux-gnu
--target=armv7a-hardfloat-linux-gnueabi
--with-ld=/usr/bin/armv7a-hardfloat-linux-gnueabi-ld
--with-as=/usr/bin/armv7a-hardfloat-linux-gnueabi-as --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-269006-checking-yes-rtl-df-extra-armv7a-hardfloat
Thread model: posix
gcc version 9.0.1 20190219 (experimental) (GCC)
The value is 0xffffffff instead of 0xff. It seems to come from this
instruction:
main:
@ args = 0, pretend = 0, frame = 0
@ frame_needed = 0, uses_anonymous_args = 0
push {r4, r5, r6, lr} @
@ testcase.c:12: d = __builtin_bswap64 (a);
mov r1, #0 @ tmp173,
@ testcase.c:12: d = __builtin_bswap64 (a);
ldr r3, .L9 @ tmp140,
str r1, [r3] @ tmp173, d
@ testcase.c:13: b = __builtin_sub_overflow ((u8) - e, (u32) d, &g);
mvn r2, #0 @ _19,
and r1, r1, #1 @ tmp147, _19,
g is in r2, == 0xffffffff
