Bug 111578

Summary:	ineg of b2i32 optimization does not trigger
Product:	Mesa	Reporter:	Ian Romanick <idr>
Component:	glsl-compiler	Assignee:	mesa-dev
Status:	RESOLVED MOVED	QA Contact:	Intel 3D Bugs Mailing List <intel-3d-bugs>
Severity:	minor
Priority:	not set
Version:	unspecified
Hardware:	All
OS:	All
Whiteboard:
i915 platform:		i915 features:

Description Ian Romanick 2019-09-06 16:42:34 UTC

This is mostly a note to myself.

While looking at bug #111490, I noticed many instances of patterns like

        vec1 32 ssa_127 = ior ssa_125, ssa_126
        vec1 32 ssa_128 = b2i32 ssa_127
        vec1 32 ssa_129 = ineg ssa_128

I thought I'd add an optimization to clean this up, but it already exists:

dca6cd9ce651 src/compiler/nir/nir_opt_algebraic.py (Jason Ekstrand                 2018-11-07 13:43:40 -0600  550)    (('ineg', ('b2i32', 'a@32')), a),

Why doesn't the existing transformation trigger?

Comment 1 Ian Romanick 2019-09-07 14:41:34 UTC

I haven't verified yet, but a 'git bisect run' that I let go over night says,

44227453ec03f5462f1cff5760909a9dba95c61a is the first bad commit
commit 44227453ec03f5462f1cff5760909a9dba95c61a
Author: Jason Ekstrand <jason.ekstrand@intel.com>
Date:   Fri Oct 19 11:14:47 2018 -0500

    nir: Switch to using 1-bit Booleans for almost everything
    
    This is a squash of a few distinct changes:
    
        glsl,spirv: Generate 1-bit Booleans
    
        Revert "Use 32-bit opcodes in the NIR producers and optimizations"
    
        Revert "nir/builder: Generate 32-bit bool opcodes transparently"
    
        nir/builder: Generate 1-bit Booleans in nir_build_imm_bool
    
    Reviewed-by: Eric Anholt <eric@anholt.net>
    Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
    Tested-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>

:040000 040000 704b07a7770ac6639a1d7359e7f4af20becfc7d3 4376841397ec5ade287aa9dc38727206cb6efc63 M	src

Comment 2 Ian Romanick 2019-09-09 17:53:53 UTC

Looking at the commit, the reason for the regression is obvious.  The nir_lower_bool_to_int32 pass happens after the last nir_opt_algebraic, so the pattern in nir_opt_algebraic never sees a ('b2i32', 'a@32').  It's effectively dead code.

Comment 3 GitLab Migration User 2019-09-18 19:46:38 UTC

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