[Bug target/105556] RA assigns an MMA vector input operand to vs0-vs31 causing an MMA accumulator to be spilled
cvs-commit at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Fri May 20 23:00:51 GMT 2022
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105556
--- 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 memory,
leading to poor performance. The solution here is to replace the "wa"
constraints for the vector input operands in the MMA instruction patterns
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)
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