[Mesa-dev] [PATCH] st/mesa: remove copy-propagation pass
Brian Paul
brianp at vmware.com
Wed Mar 25 11:59:36 PDT 2015
Will removing this pass have much effect on the number of temp regs
used? It looks like more instructions may be emitted w/out this pass.
We're kind of sensitive to that in the VMware driver.
-Brian
On 03/25/2015 12:16 PM, Marek Olšák wrote:
> Reviewed-by: Marek Olšák <marek.olsak at amd.com>
>
> I might need to wait for other people's opinion too.
>
> Marek
>
> On Wed, Mar 25, 2015 at 6:34 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>> It's buggy and unnecessary in the presence of optimizing backends. The
>> only backend that will suffer is nv30, but... meh.
>>
>> Bugzilla: https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.freedesktop.org_show-5Fbug.cgi-3Fid-3D89759&d=AwIGaQ&c=Sqcl0Ez6M0X8aeM67LKIiDJAXVeAw-YihVMNtXt-uEs&r=T0t4QG7chq2ZwJo6wilkFznRSFy-8uDKartPGbomVj8&m=hW65RavQ_Xuvw96f61daCkas_SjeEudtADNX3BzgNQU&s=zjWC0LOuYp8NH6K072ITDgPYCCE0F_a_LCdd9zrdrhA&e=
>> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
>> ---
>> src/mesa/state_tracker/st_glsl_to_tgsi.cpp | 199 -----------------------------
>> 1 file changed, 199 deletions(-)
>>
>> diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
>> index efee4b2..0402ce3 100644
>> --- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
>> +++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
>> @@ -461,7 +461,6 @@ public:
>> int get_last_temp_read(int index);
>> int get_last_temp_write(int index);
>>
>> - void copy_propagate(void);
>> int eliminate_dead_code(void);
>>
>> void merge_two_dsts(void);
>> @@ -3757,203 +3756,6 @@ glsl_to_tgsi_visitor::get_last_temp_write(int index)
>> }
>>
>> /*
>> - * On a basic block basis, tracks available PROGRAM_TEMPORARY register
>> - * channels for copy propagation and updates following instructions to
>> - * use the original versions.
>> - *
>> - * The glsl_to_tgsi_visitor lazily produces code assuming that this pass
>> - * will occur. As an example, a TXP production before this pass:
>> - *
>> - * 0: MOV TEMP[1], INPUT[4].xyyy;
>> - * 1: MOV TEMP[1].w, INPUT[4].wwww;
>> - * 2: TXP TEMP[2], TEMP[1], texture[0], 2D;
>> - *
>> - * and after:
>> - *
>> - * 0: MOV TEMP[1], INPUT[4].xyyy;
>> - * 1: MOV TEMP[1].w, INPUT[4].wwww;
>> - * 2: TXP TEMP[2], INPUT[4].xyyw, texture[0], 2D;
>> - *
>> - * which allows for dead code elimination on TEMP[1]'s writes.
>> - */
>> -void
>> -glsl_to_tgsi_visitor::copy_propagate(void)
>> -{
>> - glsl_to_tgsi_instruction **acp = rzalloc_array(mem_ctx,
>> - glsl_to_tgsi_instruction *,
>> - this->next_temp * 4);
>> - int *acp_level = rzalloc_array(mem_ctx, int, this->next_temp * 4);
>> - int level = 0;
>> -
>> - foreach_in_list(glsl_to_tgsi_instruction, inst, &this->instructions) {
>> - assert(inst->dst[0].file != PROGRAM_TEMPORARY
>> - || inst->dst[0].index < this->next_temp);
>> -
>> - /* First, do any copy propagation possible into the src regs. */
>> - for (int r = 0; r < 3; r++) {
>> - glsl_to_tgsi_instruction *first = NULL;
>> - bool good = true;
>> - int acp_base = inst->src[r].index * 4;
>> -
>> - if (inst->src[r].file != PROGRAM_TEMPORARY ||
>> - inst->src[r].reladdr ||
>> - inst->src[r].reladdr2)
>> - continue;
>> -
>> - /* See if we can find entries in the ACP consisting of MOVs
>> - * from the same src register for all the swizzled channels
>> - * of this src register reference.
>> - */
>> - for (int i = 0; i < 4; i++) {
>> - int src_chan = GET_SWZ(inst->src[r].swizzle, i);
>> - glsl_to_tgsi_instruction *copy_chan = acp[acp_base + src_chan];
>> -
>> - if (!copy_chan) {
>> - good = false;
>> - break;
>> - }
>> -
>> - assert(acp_level[acp_base + src_chan] <= level);
>> -
>> - if (!first) {
>> - first = copy_chan;
>> - } else {
>> - if (first->src[0].file != copy_chan->src[0].file ||
>> - first->src[0].index != copy_chan->src[0].index ||
>> - first->src[0].index2D != copy_chan->src[0].index2D) {
>> - good = false;
>> - break;
>> - }
>> - }
>> - }
>> -
>> - if (good) {
>> - /* We've now validated that we can copy-propagate to
>> - * replace this src register reference. Do it.
>> - */
>> - inst->src[r].file = first->src[0].file;
>> - inst->src[r].index = first->src[0].index;
>> - inst->src[r].index2D = first->src[0].index2D;
>> - inst->src[r].has_index2 = first->src[0].has_index2;
>> -
>> - int swizzle = 0;
>> - for (int i = 0; i < 4; i++) {
>> - int src_chan = GET_SWZ(inst->src[r].swizzle, i);
>> - glsl_to_tgsi_instruction *copy_inst = acp[acp_base + src_chan];
>> - swizzle |= (GET_SWZ(copy_inst->src[0].swizzle, src_chan) << (3 * i));
>> - }
>> - inst->src[r].swizzle = swizzle;
>> - }
>> - }
>> -
>> - switch (inst->op) {
>> - case TGSI_OPCODE_BGNLOOP:
>> - case TGSI_OPCODE_ENDLOOP:
>> - /* End of a basic block, clear the ACP entirely. */
>> - memset(acp, 0, sizeof(*acp) * this->next_temp * 4);
>> - break;
>> -
>> - case TGSI_OPCODE_IF:
>> - case TGSI_OPCODE_UIF:
>> - ++level;
>> - break;
>> -
>> - case TGSI_OPCODE_ENDIF:
>> - case TGSI_OPCODE_ELSE:
>> - /* Clear all channels written inside the block from the ACP, but
>> - * leaving those that were not touched.
>> - */
>> - for (int r = 0; r < this->next_temp; r++) {
>> - for (int c = 0; c < 4; c++) {
>> - if (!acp[4 * r + c])
>> - continue;
>> -
>> - if (acp_level[4 * r + c] >= level)
>> - acp[4 * r + c] = NULL;
>> - }
>> - }
>> - if (inst->op == TGSI_OPCODE_ENDIF)
>> - --level;
>> - break;
>> -
>> - default:
>> - /* Continuing the block, clear any written channels from
>> - * the ACP.
>> - */
>> - for (int d = 0; d < 2; d++) {
>> - if (inst->dst[d].file == PROGRAM_TEMPORARY && inst->dst[d].reladdr) {
>> - /* Any temporary might be written, so no copy propagation
>> - * across this instruction.
>> - */
>> - memset(acp, 0, sizeof(*acp) * this->next_temp * 4);
>> - } else if (inst->dst[d].file == PROGRAM_OUTPUT &&
>> - inst->dst[d].reladdr) {
>> - /* Any output might be written, so no copy propagation
>> - * from outputs across this instruction.
>> - */
>> - for (int r = 0; r < this->next_temp; r++) {
>> - for (int c = 0; c < 4; c++) {
>> - if (!acp[4 * r + c])
>> - continue;
>> -
>> - if (acp[4 * r + c]->src[0].file == PROGRAM_OUTPUT)
>> - acp[4 * r + c] = NULL;
>> - }
>> - }
>> - } else if (inst->dst[d].file == PROGRAM_TEMPORARY ||
>> - inst->dst[d].file == PROGRAM_OUTPUT) {
>> - /* Clear where it's used as dst. */
>> - if (inst->dst[d].file == PROGRAM_TEMPORARY) {
>> - for (int c = 0; c < 4; c++) {
>> - if (inst->dst[d].writemask & (1 << c))
>> - acp[4 * inst->dst[d].index + c] = NULL;
>> - }
>> - }
>> -
>> - /* Clear where it's used as src. */
>> - for (int r = 0; r < this->next_temp; r++) {
>> - for (int c = 0; c < 4; c++) {
>> - if (!acp[4 * r + c])
>> - continue;
>> -
>> - int src_chan = GET_SWZ(acp[4 * r + c]->src[0].swizzle, c);
>> -
>> - if (acp[4 * r + c]->src[0].file == inst->dst[d].file &&
>> - acp[4 * r + c]->src[0].index == inst->dst[d].index &&
>> - inst->dst[d].writemask & (1 << src_chan)) {
>> - acp[4 * r + c] = NULL;
>> - }
>> - }
>> - }
>> - }
>> - }
>> - break;
>> - }
>> -
>> - /* If this is a copy, add it to the ACP. */
>> - if (inst->op == TGSI_OPCODE_MOV &&
>> - inst->dst[0].file == PROGRAM_TEMPORARY &&
>> - !(inst->dst[0].file == inst->src[0].file &&
>> - inst->dst[0].index == inst->src[0].index) &&
>> - !inst->dst[0].reladdr &&
>> - !inst->saturate &&
>> - !inst->src[0].reladdr &&
>> - !inst->src[0].reladdr2 &&
>> - !inst->src[0].negate) {
>> - for (int i = 0; i < 4; i++) {
>> - if (inst->dst[0].writemask & (1 << i)) {
>> - acp[4 * inst->dst[0].index + i] = inst;
>> - acp_level[4 * inst->dst[0].index + i] = level;
>> - }
>> - }
>> - }
>> - }
>> -
>> - ralloc_free(acp_level);
>> - ralloc_free(acp);
>> -}
>> -
>> -/*
>> * On a basic block basis, tracks available PROGRAM_TEMPORARY registers for dead
>> * code elimination.
>> *
>> @@ -5623,7 +5425,6 @@ get_mesa_program(struct gl_context *ctx,
>>
>> /* Perform optimizations on the instructions in the glsl_to_tgsi_visitor. */
>> v->simplify_cmp();
>> - v->copy_propagate();
>> while (v->eliminate_dead_code());
>>
>> v->merge_two_dsts();
>> --
>> 2.0.5
>>
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