intel/vec4: sel.cond writes the flags on Gfx4 and Gfx5

This is the equivalent of idr's
intel/fs: sel.cond writes the flags on Gfx4 and Gfx5

except for the vec4 backend.

This fixes buggy rendering seen with crocus on a qt trace.

v2 (idr): Trivial whitespace change.  Add unit tests.

v3: Fix type in comment in unit tests.  Noticed by Jason and Priit.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

Iron Lake
total instructions in shared programs: 8183077 -> 8184543 (0.02%)
instructions in affected programs: 198990 -> 200456 (0.74%)
helped: 0
HURT: 1355
HURT stats (abs)   min: 1 max: 8 x̄: 1.08 x̃: 1
HURT stats (rel)   min: 0.29% max: 6.00% x̄: 0.99% x̃: 0.70%
95% mean confidence interval for instructions value: 1.04 1.12
95% mean confidence interval for instructions %-change: 0.96% 1.03%
Instructions are HURT.

total cycles in shared programs: 238967672 -> 238962784 (<.01%)
cycles in affected programs: 4666014 -> 4661126 (-0.10%)
helped: 406
HURT: 314
helped stats (abs) min: 4 max: 54 x̄: 22.46 x̃: 18
helped stats (rel) min: <.01% max: 12.80% x̄: 1.82% x̃: 0.65%
HURT stats (abs)   min: 2 max: 112 x̄: 13.48 x̃: 12
HURT stats (rel)   min: <.01% max: 7.82% x̄: 0.81% x̃: 0.16%
95% mean confidence interval for cycles value: -8.60 -4.98
95% mean confidence interval for cycles %-change: -0.87% -0.49%
Cycles are helped.

GM45
total instructions in shared programs: 4986888 -> 4988354 (0.03%)
instructions in affected programs: 198990 -> 200456 (0.74%)
helped: 0
HURT: 1355
HURT stats (abs)   min: 1 max: 8 x̄: 1.08 x̃: 1
HURT stats (rel)   min: 0.29% max: 6.00% x̄: 0.99% x̃: 0.70%
95% mean confidence interval for instructions value: 1.04 1.12
95% mean confidence interval for instructions %-change: 0.96% 1.03%
Instructions are HURT.

total cycles in shared programs: 153577826 -> 153572938 (<.01%)
cycles in affected programs: 4666014 -> 4661126 (-0.10%)
helped: 406
HURT: 314
helped stats (abs) min: 4 max: 54 x̄: 22.46 x̃: 18
helped stats (rel) min: <.01% max: 12.80% x̄: 1.82% x̃: 0.65%
HURT stats (abs)   min: 2 max: 112 x̄: 13.48 x̃: 12
HURT stats (rel)   min: <.01% max: 7.82% x̄: 0.81% x̃: 0.16%
95% mean confidence interval for cycles value: -8.60 -4.98
95% mean confidence interval for cycles %-change: -0.87% -0.49%
Cycles are helped.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12191>

src/intel/compiler/brw_vec4_live_variables.cpp

@@ -119,7 +119,7 @@ vec4_live_variables::setup_def_use()
                }
             }
          }
-         if (inst->writes_flag()) {
+         if (inst->writes_flag(devinfo)) {
             for (unsigned c = 0; c < 4; c++) {
                if ((inst->dst.writemask & (1 << c)) &&
                    !BITSET_TEST(bd->flag_use, c)) {
@@ -229,6 +229,8 @@ vec4_live_variables::vec4_live_variables(const backend_shader *s)
       end[i] = -1;
    }
 
+   devinfo = s->compiler->devinfo;
+
    block_data = rzalloc_array(mem_ctx, struct block_data, cfg->num_blocks);
 
    bitset_words = BITSET_WORDS(num_vars);