[Bug target/113652] [14 regression] Failed bootstrap on ppc unrecognized opcode: `lfiwzx' with -mcpu=7450

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113652

Peter Bergner <bergner at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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             Status|NEW                         |ASSIGNED

--- Comment #22 from Peter Bergner <bergner at gcc dot gnu.org> ---
I kicked off a 7450 build on one of our BE system and I can confirm we hit this
error.  I also saw us generating the 2 operand form of the mfcr instruction
which also leads to an assembler error because the 7450 doesn't support that
either.

Were we are in the build is compiling libgcc and the routines for handling
KFmode values.  The build machinery is explicitly adding -mvsx -mfloat128 to
the compiler options when building those source files and that seems bogus to
me, since the 7450 does not have VSX hardware.  It's the explicit addition of
the -mvsx option to the command line that is causing the lfiwzx and 2 operand
mfcr instructions to be generated, not some internal mishandling of the
-mcpu=7450 option.

My $0.02 worth is we should be generating an error when trying to use -msx with
-mcpu=7450 or any other cpu that doesn't have VSX hardware. I also don't think
we should be building these KFmode files which require VSX when the underlying
cpu we're targeting doesn't support it.