https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124316
Bug ID: 124316
Summary: _ptwrite64() is generating 32bit PTWRITE instruction
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: target
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 63800
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=63800&action=edit
reduced testcase
Output:
$ gcc -O -mptwrite testcase.c -c
/tmp/cchACnnz.s: Assembler messages:
/tmp/cchACnnz.s:8: Warning: no instruction mnemonic suffix given and no
register operands; using default for `ptwrite'
/tmp/cchACnnz.s:9: Warning: no instruction mnemonic suffix given and no
register operands; using default for `ptwrite'
Both _ptwrite32() and _ptwrite64() generate the same instruction when using
memory operand:
$ gcc -O -mptwrite testcase.c -S -o- | grep ptwrite
ptwrite ull(%rip)
ptwrite u(%rip)
Interestingly this is OK with -masm=intel:
$ gcc -O -mptwrite testcase.c -S -o- -masm=intel | grep ptwrite
ptwrite QWORD PTR "ull"[rip]
ptwrite DWORD PTR "u"[rip]
$ gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-amd64/bin/gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-20260228053546-r16-7823-g5d12019d75b196-checking-yes-rtl-df-extra-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/16.0.1/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
--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 --enable-libsanitizer
--disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-20260228053546-r16-7823-g5d12019d75b196-checking-yes-rtl-df-extra-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 16.0.1 20260227 (experimental) (GCC)
