pan/midgard: Extend copy-propagation to swizzles

pan/midgard: Extend copy-propagation to swizzles

We can compose them when we rewrite, which is.. more code.. but helps.

total instructions in shared programs: 3611 -> 3513 (-2.71%)
instructions in affected programs: 672 -> 574 (-14.58%)
helped: 11
HURT: 2
helped stats (abs) min: 2 max: 14 x̄: 9.09 x̃: 10
helped stats (rel) min: 5.71% max: 24.56% x̄: 17.99% x̃: 18.87%
HURT stats (abs)   min: 1 max: 1 x̄: 1.00 x̃: 1
HURT stats (rel)   min: 1.19% max: 2.08% x̄: 1.64% x̃: 1.64%
95% mean confidence interval for instructions value: -10.45 -4.62
95% mean confidence interval for instructions %-change: -20.07% -9.87%
Instructions are helped.

total bundles in shared programs: 2117 -> 2067 (-2.36%)
bundles in affected programs: 356 -> 306 (-14.04%)
helped: 11
HURT: 0
helped stats (abs) min: 1 max: 7 x̄: 4.55 x̃: 5
helped stats (rel) min: 4.55% max: 15.22% x̄: 13.63% x̃: 14.71%
95% mean confidence interval for bundles value: -5.64 -3.45
95% mean confidence interval for bundles %-change: -15.71% -11.55%
Bundles are helped.

total quadwords in shared programs: 3567 -> 3468 (-2.78%)
quadwords in affected programs: 695 -> 596 (-14.24%)
helped: 11
HURT: 1
helped stats (abs) min: 2 max: 14 x̄: 9.09 x̃: 10
helped stats (rel) min: 5.56% max: 21.88% x̄: 14.97% x̃: 15.15%
HURT stats (abs)   min: 1 max: 1 x̄: 1.00 x̃: 1
HURT stats (rel)   min: 2.38% max: 2.38% x̄: 2.38% x̃: 2.38%
95% mean confidence interval for quadwords value: -10.96 -5.54
95% mean confidence interval for quadwords %-change: -17.42% -9.63%
Quadwords are helped.

total registers in shared programs: 391 -> 383 (-2.05%)
registers in affected programs: 46 -> 38 (-17.39%)
helped: 9
HURT: 1
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: 25.00% max: 25.00% x̄: 25.00% x̃: 25.00%
HURT stats (abs)   min: 1 max: 1 x̄: 1.00 x̃: 1
HURT stats (rel)   min: 10.00% max: 10.00% x̄: 10.00% x̃: 10.00%
95% mean confidence interval for registers value: -1.25 -0.35
95% mean confidence interval for registers %-change: -29.42% -13.58%
Registers are helped.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>