https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106743
Bug ID: 106743
Summary: Illegal assembly code with -march=skylake
Product: gcc
Version: 12.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: stayprivate at gmail dot com
Target Milestone: ---
#include <stdint.h>
#include <iostream>
#define swapw(__val)
\
({
\
uint16_t __tmp = __val;
\
__asm__("xchgb %b0, %h0" : "=q"(__tmp) : "0"(__tmp));
\
__tmp;
\
})
int main()
{
int value = rand();
int a = swapw(value);
std::cout << std::hex << "First value is " << value << " " << a << '\n';
}
Compile with gcc (gcc 12 on Ubuntu ), and also with trunk. As shown on
https://godbolt.org/z/oGn9WK6GE the assembler will generate the following
error:
: register type mismatch for `xchg'
This is only when using -march=skylake or above and using -O1 or above.
The code works in gcc-9/10/11.
