[Bug target/88195] New: misleading error message for unsupported builtin

[andi-gcc at firstfloor dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88195

            Bug ID: 88195
           Summary: misleading error message for unsupported builtin
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: andi-gcc at firstfloor dot org
  Target Milestone: ---
            Target: x86_64

On x86, when using a builtin that is not supported by the target configuration,
e.g.

gcc -c -m32 -ptwrite t.c.c
with t.c being
void f(void)
{
        __builtin_ia32_ptwrite64 (1);
}

I get

t.c:4:2: error: '__builtin_ia32_ptwrite64' needs isa option -mx32 -mptwrite



While technically correct, -mx32 would enable the 64bit builtin, I suspect for
near all users they would like to use -m64, or better not specifying -m32. So
it should mention that it is incompatible with -m32.