pan/bi: Don't optimize if without else

pan/bi: Don't optimize if without else

We need to emit a jump over the else body when constructing the IR, even if the
else body appears empty in NIR, because instructions could be added when
going out-of-SSA. This optimization should instead happen post-RA, but doing so
is nontrivial and the cycle count regression is minimal, so punting on this for
now.

total instructions in shared programs: 2728364 -> 2731495 (0.11%)
instructions in affected programs: 580462 -> 583593 (0.54%)
helped: 0
HURT: 1272
HURT stats (abs)   min: 1.0 max: 17.0 x̄: 2.46 x̃: 2
HURT stats (rel)   min: 0.09% max: 22.22% x̄: 0.88% x̃: 0.59%
95% mean confidence interval for instructions value: 2.37 2.56
95% mean confidence interval for instructions %-change: 0.80% 0.97%
Instructions are HURT.

total cycles in shared programs: 140628.52 -> 140631.50 (<.01%)
cycles in affected programs: 474.45 -> 477.44 (0.63%)
helped: 0
HURT: 116
HURT stats (abs)   min: 0.015625 max: 0.0625 x̄: 0.03 x̃: 0
HURT stats (rel)   min: 0.21% max: 9.09% x̄: 1.16% x̃: 0.39%
95% mean confidence interval for cycles value: 0.02 0.03
95% mean confidence interval for cycles %-change: 0.88% 1.43%
Cycles are HURT.

total cvt in shared programs: 14816.20 -> 14865.12 (0.33%)
cvt in affected programs: 4954.31 -> 5003.23 (0.99%)
helped: 0
HURT: 1272
HURT stats (abs)   min: 0.015625 max: 0.265625 x̄: 0.04 x̃: 0
HURT stats (rel)   min: 0.16% max: 28.57% x̄: 1.88% x̃: 1.17%
95% mean confidence interval for cvt value: 0.04 0.04
95% mean confidence interval for cvt %-change: 1.74% 2.02%
Cvt are HURT.

total quadwords in shared programs: 1476536 -> 1478512 (0.13%)
quadwords in affected programs: 54496 -> 56472 (3.63%)
helped: 0
HURT: 247
HURT stats (abs)   min: 8.0 max: 8.0 x̄: 8.00 x̃: 8
HURT stats (rel)   min: 0.93% max: 20.00% x̄: 5.78% x̃: 4.17%
95% mean confidence interval for quadwords value: 8.00 8.00
95% mean confidence interval for quadwords %-change: 5.21% 6.34%
Quadwords are HURT.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17794>