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nir: Don't reassociate add/mul chains containing only constants

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The idea here is to reassociate a * (b * c) into (a * c) * b, when
b is a non-constant value, but a and c are constants, allowing them
to be combined.

But nothing was enforcing that 'b' must be non-constant, which meant
that running opt_algebraic in a loop would never terminate if the IR
contained non-folded constant expressions like 256 * 0.5 * 2.  Normally,
we call constant folding in such a loop too, but IMO it's better for
nir_opt_algebraic to be robust and not rely on that.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109581
Fixes: 32e266a9a5 i965: Compile fp64 funcs only if we do not have 64-bit hardware support

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
(cherry picked from commit 535251487b)
This commit is contained in:
Kenneth Graunke 2019-02-15 14:52:20 -08:00 • committed by Dylan Baker
parent 385b736238
commit 69ebf4569a
1 changed files with 5 additions and 5 deletions
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10
src/compiler/nir/nir_opt_algebraic.py
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@ -618,11 +618,11 @@ optimizations = [
# Reassociate constants in add/mul chains so they can be folded together.
# For now, we mostly only handle cases where the constants are separated by
# a single non-constant. We could do better eventually.
(('~fmul', '#a', ('fmul', b, '#c')), ('fmul', ('fmul', a, c), b)),
(('imul', '#a', ('imul', b, '#c')), ('imul', ('imul', a, c), b)),
(('~fadd', '#a', ('fadd', b, '#c')), ('fadd', ('fadd', a, c), b)),
(('~fadd', '#a', ('fneg', ('fadd', b, '#c'))), ('fadd', ('fadd', a, ('fneg', c)), ('fneg', b))),
(('iadd', '#a', ('iadd', b, '#c')), ('iadd', ('iadd', a, c), b)),
(('~fmul', '#a', ('fmul', 'b(is_not_const)', '#c')), ('fmul', ('fmul', a, c), b)),
(('imul', '#a', ('imul', 'b(is_not_const)', '#c')), ('imul', ('imul', a, c), b)),
(('~fadd', '#a', ('fadd', 'b(is_not_const)', '#c')), ('fadd', ('fadd', a, c), b)),
(('~fadd', '#a', ('fneg', ('fadd', 'b(is_not_const)', '#c'))), ('fadd', ('fadd', a, ('fneg', c)), ('fneg', b))),
(('iadd', '#a', ('iadd', 'b(is_not_const)', '#c')), ('iadd', ('iadd', a, c), b)),
# By definition...
(('bcsel', ('ige', ('find_lsb', a), 0), ('find_lsb', a), -1), ('find_lsb', a)),