pan/bi: Add SSA-based scalar copy propagation

pan/bi: Add SSA-based scalar copy propagation

This is a very simple (and slow...) copyprop pass. It's good enough to
get rid of redundant moves from FAU, but it doesn't help for vector
combines.

total instructions in shared programs: 175219 -> 169141 (-3.47%)
instructions in affected programs: 91439 -> 85361 (-6.65%)
helped: 599
HURT: 0
helped stats (abs) min: 1 max: 112 x̄: 10.15 x̃: 6
helped stats (rel) min: 0.30% max: 33.33% x̄: 8.61% x̃: 8.04%
95% mean confidence interval for instructions value: -11.06 -9.24
95% mean confidence interval for instructions %-change: -9.07% -8.16%
Instructions are helped.

total nops in shared programs: 120011 -> 121049 (0.86%)
nops in affected programs: 47355 -> 48393 (2.19%)
helped: 110
HURT: 309
helped stats (abs) min: 1 max: 6 x̄: 2.07 x̃: 2
helped stats (rel) min: 0.44% max: 16.67% x̄: 3.59% x̃: 3.16%
HURT stats (abs)   min: 1 max: 56 x̄: 4.10 x̃: 2
HURT stats (rel)   min: 0.32% max: 80.85% x̄: 6.85% x̃: 3.12%
95% mean confidence interval for nops value: 1.86 3.09
95% mean confidence interval for nops %-change: 3.08% 5.14%
Nops are HURT.

total clauses in shared programs: 40576 -> 40388 (-0.46%)
clauses in affected programs: 3074 -> 2886 (-6.12%)
helped: 106
HURT: 0
helped stats (abs) min: 1 max: 4 x̄: 1.77 x̃: 2
helped stats (rel) min: 0.42% max: 22.22% x̄: 7.17% x̃: 6.90%
95% mean confidence interval for clauses value: -1.91 -1.63
95% mean confidence interval for clauses %-change: -7.80% -6.53%
Clauses are helped.

total quadwords in shared programs: 146590 -> 144937 (-1.13%)
quadwords in affected programs: 59475 -> 57822 (-2.78%)
helped: 493
HURT: 1
helped stats (abs) min: 1 max: 28 x̄: 3.35 x̃: 2
helped stats (rel) min: 0.28% max: 15.38% x̄: 4.08% x̃: 3.85%
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: -3.61 -3.08
95% mean confidence interval for quadwords %-change: -4.33% -3.81%
Quadwords are helped.

total spills in shared programs: 1106 -> 1106 (0.00%)
spills in affected programs: 0 -> 0
helped: 0
HURT: 0

total fills in shared programs: 2241 -> 2241 (0.00%)
fills in affected programs: 0 -> 0
helped: 0
HURT: 0

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8973>