https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93170
Bug ID: 93170
Summary: [10 Regression] wrong code due to use of a
call-clobbered register
Product: gcc
Version: 10.0
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: x86_64-pc-linux-gnu
Created attachment 47595
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47595&action=edit
reduced testcase
Output:
$ x86_64-pc-linux-gnu-gcc -O2 -frename-registers -fno-tree-forwprop
-fno-tree-fre -fira-algorithm=priority -mstringop-strategy=loop
--param=hot-bb-frequency-fraction=0 testcase.c -Wno-psabi
$ ./a.out
Aborted
In the assembly output:
...
# testcase.c:17: d = __builtin_popcountll (-((v64u8) i)[0]);
movsx rdi, esi # tmp233, tmp232
mov QWORD PTR [rsp+32], r10 # %sfp, _70
mov QWORD PTR [rsp+40], r11 # %sfp, _70
mov QWORD PTR [rsp+16], rbx # %sfp, _67
call __popcountdi2 #
...
# testcase.c:16: j >>= ((v64u128) h <= j);
shrd r12, rsi, cl # tmp254,, tmp253
xor ebx, ebx #
# testcase.c:18: return a + g + j;
mov QWORD PTR [rsp+128], rax #, tmp251
# testcase.c:16: j >>= ((v64u128) h <= j);
shr rsi, cl #, tmp253
...
The __popcountdi2 call clobbers rsi, and the caller uses the clobbered value.
$ x86_64-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-amd64/bin/x86_64-pc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-279889-checking-yes-rtl-df-extra-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/10.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
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 --build=x86_64-pc-linux-gnu
--host=x86_64-pc-linux-gnu --target=x86_64-pc-linux-gnu
--with-ld=/usr/bin/x86_64-pc-linux-gnu-ld
--with-as=/usr/bin/x86_64-pc-linux-gnu-as --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-279889-checking-yes-rtl-df-extra-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.0.0 20200105 (experimental) (GCC)
