diff options
| -rw-r--r-- | src/mesa/state_tracker/st_glsl_to_tgsi.cpp | 140 |
1 files changed, 140 insertions, 0 deletions
diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp index 721ba28d61f..d47364fabb6 100644 --- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp +++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp @@ -208,6 +208,7 @@ public: int sampler; /**< sampler index */ int tex_target; /**< One of TEXTURE_*_INDEX */ GLboolean tex_shadow; + int dead_mask; /**< Used in dead code elimination */ class function_entry *function; /* Set on TGSI_OPCODE_CAL or TGSI_OPCODE_BGNSUB */ }; @@ -384,6 +385,7 @@ public: void copy_propagate(void); void eliminate_dead_code(void); + int eliminate_dead_code_advanced(void); void merge_registers(void); void renumber_registers(void); @@ -480,6 +482,7 @@ glsl_to_tgsi_visitor::emit(ir_instruction *ir, unsigned op, inst->src[1] = src1; inst->src[2] = src2; inst->ir = ir; + inst->dead_mask = 0; inst->function = NULL; @@ -3257,6 +3260,142 @@ glsl_to_tgsi_visitor::eliminate_dead_code(void) } } +/* + * On a basic block basis, tracks available PROGRAM_TEMPORARY registers for dead + * code elimination. This is less primitive than eliminate_dead_code(), as it + * is per-channel and can detect consecutive writes without a read between them + * as dead code. However, there is some dead code that can be eliminated by + * eliminate_dead_code() but not this function - for example, this function + * cannot eliminate an instruction writing to a register that is never read and + * is the only instruction writing to that register. + * + * The glsl_to_tgsi_visitor lazily produces code assuming that this pass + * will occur. + */ +int +glsl_to_tgsi_visitor::eliminate_dead_code_advanced(void) +{ + glsl_to_tgsi_instruction **writes = rzalloc_array(mem_ctx, + glsl_to_tgsi_instruction *, + this->next_temp * 4); + int *write_level = rzalloc_array(mem_ctx, int, this->next_temp * 4); + int level = 0; + int removed = 0; + + foreach_iter(exec_list_iterator, iter, this->instructions) { + glsl_to_tgsi_instruction *inst = (glsl_to_tgsi_instruction *)iter.get(); + + assert(inst->dst.file != PROGRAM_TEMPORARY + || inst->dst.index < this->next_temp); + + switch (inst->op) { + case TGSI_OPCODE_BGNLOOP: + case TGSI_OPCODE_ENDLOOP: + /* End of a basic block, clear the write array entirely. + * FIXME: This keeps us from killing dead code when the writes are + * on either side of a loop, even when the register isn't touched + * inside the loop. + */ + memset(writes, 0, sizeof(*writes) * this->next_temp * 4); + break; + + case TGSI_OPCODE_IF: + ++level; + break; + + case TGSI_OPCODE_ENDIF: + --level; + break; + + case TGSI_OPCODE_ELSE: + /* Clear all channels written inside the preceding if block from the + * write array, but leave those that were not touched. + * + * FIXME: This destroys opportunities to remove dead code inside of + * IF blocks that are followed by an ELSE block. + */ + for (int r = 0; r < this->next_temp; r++) { + for (int c = 0; c < 4; c++) { + if (!writes[4 * r + c]) + continue; + + if (write_level[4 * r + c] >= level) + writes[4 * r + c] = NULL; + } + } + break; + + default: + /* Continuing the block, clear any channels from the write array that + * are read by this instruction. + */ + for (int i = 0; i < 4; i++) { + if (inst->src[i].file == PROGRAM_TEMPORARY && inst->src[i].reladdr){ + /* Any temporary might be read, so no dead code elimination + * across this instruction. + */ + memset(writes, 0, sizeof(*writes) * this->next_temp * 4); + } else if (inst->src[i].file == PROGRAM_TEMPORARY) { + /* Clear where it's used as src. */ + int src_chans = 1 << GET_SWZ(inst->src[i].swizzle, 0); + src_chans |= 1 << GET_SWZ(inst->src[i].swizzle, 1); + src_chans |= 1 << GET_SWZ(inst->src[i].swizzle, 2); + src_chans |= 1 << GET_SWZ(inst->src[i].swizzle, 3); + + for (int c = 0; c < 4; c++) { + if (src_chans & (1 << c)) { + writes[4 * inst->src[i].index + c] = NULL; + } + } + } + } + break; + } + + /* If this instruction writes to a temporary, add it to the write array. + * If there is already an instruction in the write array for one or more + * of the channels, flag that channel write as dead. + */ + if (inst->dst.file == PROGRAM_TEMPORARY && + !inst->dst.reladdr && + !inst->saturate) { + for (int c = 0; c < 4; c++) { + if (inst->dst.writemask & (1 << c)) { + if (writes[4 * inst->dst.index + c]) { + if (write_level[4 * inst->dst.index + c] < level) + continue; + else + writes[4 * inst->dst.index + c]->dead_mask |= (1 << c); + } + writes[4 * inst->dst.index + c] = inst; + write_level[4 * inst->dst.index + c] = level; + } + } + } + } + + /* Now actually remove the instructions that are completely dead and update + * the writemask of other instructions with dead channels. + */ + foreach_iter(exec_list_iterator, iter, this->instructions) { + glsl_to_tgsi_instruction *inst = (glsl_to_tgsi_instruction *)iter.get(); + + if (!inst->dead_mask || !inst->dst.writemask) + continue; + else if (inst->dead_mask == inst->dst.writemask) { + iter.remove(); + delete inst; + removed++; + } else + inst->dst.writemask &= ~(inst->dead_mask); + } + + ralloc_free(write_level); + ralloc_free(writes); + + return removed; +} + /* Merges temporary registers together where possible to reduce the number of * registers needed to run a program. * @@ -4269,6 +4408,7 @@ get_mesa_program(struct gl_context *ctx, */ if (!v->indirect_addr_temps) { v->copy_propagate(); + while (v->eliminate_dead_code_advanced()); v->eliminate_dead_code(); v->merge_registers(); v->renumber_registers(); |