[Bug inline-asm/101393] New: PowerPC32 inline assembly broken by commit 2d94f7dea9c73ef3c116a0ddc722724578a860fe

["sirl at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101393

            Bug ID: 101393
           Summary: PowerPC32 inline assembly broken by commit
                    2d94f7dea9c73ef3c116a0ddc722724578a860fe
           Product: gcc
           Version: 10.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: inline-asm
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sirl at gcc dot gnu.org
  Target Milestone: ---

A PowerPC32 GCC configured with "--target=powerpc-unknown-eabi
--enable-languages=c,c++ --with-cpu=403" compiling this snippet:

void test(void)
{
        __asm__ __volatile__("dcread 3,3,0");
}

with "powerpc-unknown-eabi-gcc-10 -c test-ppc.c -o test-ppc-gcc10.o" results
in:

> objdump -d test-ppc-gcc10.o

test-ppc-gcc10.o:     file format elf32-powerpc


Disassembly of section .text:

00000000 <test>:
   0:   7c 63 02 8c     dcread  r3,r3,r0
   4:   4e 80 00 20     blr

With "powerpc-unknown-eabi-gcc-9 -c test-ppc.c -o test-ppc-gcc9.o":

> objdump -d test-ppc-gcc9.o 

test-ppc-gcc9.o:     file format elf32-powerpc


Disassembly of section .text:

00000000 <test>:
   0:   7c 63 03 cc     dcread  r3,r3,r0
   4:   4e 80 00 20     blr

Note the changed encoding for dcread, GCC-9 correctly produces an opcode for
PPC403/PPC440, while GCC-10 onwards produces the opcode for PPC476.
This is caused by the unconditional output of ".machine ppc" by GCC-10,
seemingly overriding the commandline to gas (-m403 -many).