Re: [PATCH] nvptx: Fix and use BI mode logic instructions (e.g. and.pred).

[Tom de Vries via Gcc-patches]

On 1/16/22 12:49, Roger Sayle wrote:

This patch adds support for nvptx's BImode and.pred, or.pred and
xor.pred instructions.  Technically, nvptx.md previously defined
andbi3, iorbi3 and xorbi3 instructions, but the assembly language
mnemonic output for these was incorrect (e.g. and.b1) and would be
rejected by the ptxas assembler.

Thanks for catching and fixing that :) !

The most significant part of this
patch is the new define_split which teaches the compiler to actually
use these instructions when appropriate (exposing the latent bug above).

After https://gcc.gnu.org/pipermail/gcc-patches/2022-January/587999.html
(still awaiting review/approval), the function:

int foo(int x, int y) { return (x==21) && (y==69); }

when compiled with -O2 produces:

                 mov.u32 %r26, %ar0;
                 mov.u32 %r27, %ar1;
                 setp.eq.u32     %r31, %r26, 21;
                 setp.eq.u32     %r34, %r27, 69;
                 selp.u32        %r37, 1, 0, %r31;
                 selp.u32        %r38, 1, 0, %r34;
                 and.b32 %value, %r37, %r38;

with this patch we now save an extra instruction and generate:

                 mov.u32 %r26, %ar0;
                 mov.u32 %r27, %ar1;
                 setp.eq.u32     %r31, %r26, 21;
                 setp.eq.u32     %r34, %r27, 69;
                 and.pred        %r39, %r34, %r31;
                 selp.u32        %value, 1, 0, %r39;

This patch has been tested (on top of the patch mentioned above) on
nvptx-none hosted on x86_64-pc-linux-gnu (including newlib) with a
make and make -k check with no new failures.  Ok for mainline?

LGTM, applied.

Thanks,
- Tom

2022-01-16  Roger Sayle  <ro...@nextmovesoftware.com>

gcc/ChangeLog
        * config/nvptx/nvptx.md (any_logic): Move code iterator earlier
        in machine description.
        (logic): Move code attribute earlier in machine description.
        (ilogic): New code attribute, like logic but "ior" for IOR.
        (and<mode>3, ior<mode>3, xor<mode>3): Delete. Replace with...
        (<ilogic><mode>3): New define_insn for HSDIM logic operations.
        (<ilogic>bi3): New define_insn for BI mode logic operations.
        (define_split): Lower logic operations from integer modes to
        BI mode predicate operations.

gcc/testsuite/ChangeLog
        * gcc.target/nvptx/bool-2.c: New test case for and.pred.
        * gcc.target/nvptx/bool-3.c: New test case for or.pred.
        * gcc.target/nvptx/bool-4.c: New test case for xor.pred.


Many thanks in advance.

Roger
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