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Subject: [Bug target/105556] RA assigns an MMA vector input operand to
 vs0-vs31 causing an MMA accumulator to be spilled
Date: Fri, 20 May 2022 23:00:51 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105556

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Peter Bergner
<bergner@gcc.gnu.org>:

https://gcc.gnu.org/g:c83d78585078d6918853fbe0f74a3a78e88e3e32

commit r12-8406-gc83d78585078d6918853fbe0f74a3a78e88e3e32
Author: Peter Bergner <bergner@linux.ibm.com>
Date:   Tue May 17 21:09:29 2022 -0500

    rs6000: Prefer assigning the MMA vector operands to altivec registers
[PR105556]

    When optimizing the DGEMM kernel in OpenBLAS to use MMA, the MMA code
    uses all 8 accumulators, which overlap all vs0-vs31 vector registers.
    Current trunk assigns one of the normal vector inputs to one of the MMA
    instructions, which forces us to spill one of the accumulators to memor=
y,
    leading to poor performance.  The solution here is to replace the "wa"
    constraints for the vector input operands in the MMA instruction patter=
ns
    with "v,?wa" so that we prefer using the altivec registers vs32-vs63
    over the vs0-vs31 registers.

    2022-05-17  Peter Bergner  <bergner@linux.ibm.com>
                Segher Boessenkool  <segher@kernel.crashing.org>

    gcc/
            PR target/105556
            * config/rs6000/mma.md (mma_<vv>, mma_<avv>, mma_<pv>, mma_<apv=
>,
            mma_<vvi4i4i8>, mma_<avvi4i4i8>, mma_<vvi4i4i2>, mma_<avvi4i4i2=
>,
            mma_<vvi4i4>, mma_<avvi4i4>, mma_<pvi4i2>, mma_<apvi4i2>,
            mma_<vvi4i4i4>, mma_<avvi4i4i4>): Replace "wa" constraints with
"v,?wa".
            Update other operands accordingly.

    (cherry picked from commit c6e36f05fbb081abb068958d8900ad34b303a70b)=