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panfrost/midgard: Dead code eliminate MIR

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We reshuffle the existing "dead move elimination" pass into a generic
dead code elimination layer, fixing bugs incurred with looping in the
process.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
This commit is contained in:
Alyssa Rosenzweig 2019-04-21 16:11:11 +00:00
parent 328a5ef598
commit 84f09ff433
1 changed files with 10 additions and 15 deletions
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25
src/gallium/drivers/panfrost/midgard/midgard_compile.c
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@ -643,8 +643,6 @@ print_mir_block(midgard_block *block)
printf("}\n"); printf("}\n");
} }
static void static void
attach_constants(compiler_context *ctx, midgard_instruction *ins, void *constants, int name) attach_constants(compiler_context *ctx, midgard_instruction *ins, void *constants, int name)
{ {
@ -3045,26 +3043,18 @@ map_ssa_to_alias(compiler_context *ctx, int *ref)
} }
} }
#define AS_SRC(to, u) \ /* Basic dead code elimination on the MIR itself, which cleans up e.g. the
int q##to = ins->alu.src2; \ * texture pipeline */
midgard_vector_alu_src *to = (midgard_vector_alu_src *) &q##to;
/* Removing unused moves is necessary to clean up the texture pipeline results.
*
* To do so, we find moves in the MIR. We check if their destination is live later. If it's not, the move is redundant. */
static void static void
midgard_eliminate_orphan_moves(compiler_context *ctx, midgard_block *block) midgard_opt_dead_code_eliminate(compiler_context *ctx, midgard_block *block)
{ {
mir_foreach_instr_in_block_safe(block, ins) { mir_foreach_instr_in_block_safe(block, ins) {
if (ins->type != TAG_ALU_4) continue; if (ins->type != TAG_ALU_4) continue;
if (ins->compact_branch) continue;
if (ins->alu.op != midgard_alu_op_fmov) continue;
if (ins->ssa_args.dest >= SSA_FIXED_MINIMUM) continue; if (ins->ssa_args.dest >= SSA_FIXED_MINIMUM) continue;
if (midgard_is_pinned(ctx, ins->ssa_args.dest)) continue; if (midgard_is_pinned(ctx, ins->ssa_args.dest)) continue;
if (is_live_after(ctx, block, ins, ins->ssa_args.dest)) continue; if (is_live_after(ctx, block, ins, ins->ssa_args.dest)) continue;
mir_remove_instruction(ins); mir_remove_instruction(ins);
@ -3321,7 +3311,6 @@ emit_block(compiler_context *ctx, nir_block *block)
actualise_ssa_to_alias(ctx); actualise_ssa_to_alias(ctx);
midgard_emit_store(ctx, this_block); midgard_emit_store(ctx, this_block);
midgard_eliminate_orphan_moves(ctx, this_block);
midgard_pair_load_store(ctx, this_block); midgard_pair_load_store(ctx, this_block);
/* Append fragment shader epilogue (value writeout) */ /* Append fragment shader epilogue (value writeout) */
@ -3608,6 +3597,12 @@ midgard_compile_shader_nir(nir_shader *nir, midgard_program *program, bool is_bl
util_dynarray_init(compiled, NULL); util_dynarray_init(compiled, NULL);
/* Peephole optimizations */
mir_foreach_block(ctx, block) {
midgard_opt_dead_code_eliminate(ctx, block);
}
/* Schedule! */ /* Schedule! */
schedule_program(ctx); schedule_program(ctx);