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pan/mdg: Don't assign destination in writeout block to r1

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It will misbehave.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5513>
This commit is contained in:
Alyssa Rosenzweig 2020-06-30 13:52:05 -04:00
parent d838cb96a5
commit 5a43f7fcce
1 changed files with 51 additions and 1 deletions
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52
src/panfrost/midgard/midgard_ra.c
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@ -466,7 +466,11 @@ allocate_registers(compiler_context *ctx, bool *spilled)
if (!ctx->temp_count)
return NULL;
struct lcra_state *l = lcra_alloc_equations(ctx->temp_count, 5);
/* Initialize LCRA. Allocate an extra node at the end for a precoloured
* r1 for interference */
struct lcra_state *l = lcra_alloc_equations(ctx->temp_count + 1, 5);
unsigned node_r1 = ctx->temp_count;
/* Starts of classes, in bytes */
l->class_start[REG_CLASS_WORK] = 16 * 0;
@ -635,6 +639,52 @@ allocate_registers(compiler_context *ctx, bool *spilled)
l->solutions[ins->dest] = (16 * 1) + COMPONENT_W * 4;
}
/* Destinations of instructions in a writeout block cannot be assigned
* to r1 unless they are actually used as r1 from the writeout itself,
* since the writes to r1 are special. A code sequence like:
*
* sadd.fmov r1.x, [...]
* vadd.fadd r0, r1, r2
* [writeout branch]
*
* will misbehave since the r1.x write will be interpreted as a
* gl_FragDepth write so it won't show up correctly when r1 is read in
* the following segment. We model this as interference.
*/
l->solutions[node_r1] = (16 * 1);
mir_foreach_block(ctx, _blk) {
midgard_block *blk = (midgard_block *) _blk;
mir_foreach_bundle_in_block(blk, v) {
/* We need at least a writeout and nonwriteout instruction */
if (v->instruction_count < 2)
continue;
/* Branches always come at the end */
midgard_instruction *br = v->instructions[v->instruction_count - 1];
if (!br->writeout)
continue;
for (signed i = v->instruction_count - 2; i >= 0; --i) {
midgard_instruction *ins = v->instructions[i];
if (ins->dest >= ctx->temp_count)
continue;
bool used_as_r1 = (br->dest == ins->dest);
mir_foreach_src(br, s)
used_as_r1 |= (s > 0) && (br->src[s] == ins->dest);
if (!used_as_r1)
lcra_add_node_interference(l, ins->dest, mir_bytemask(ins), node_r1, 0xFFFF);
}
}
}
/* Precolour blend input to r0. Note writeout is necessarily at the end
* and blend shaders are single-RT only so there is only a single
* writeout block, so this cannot conflict with the writeout r0 (there