Mesa (master): r300/compiler: Unroll loops that have a constant number of iterations.
Marek Olšák
mareko at kemper.freedesktop.org
Fri Jun 11 20:24:02 UTC 2010
Module: Mesa
Branch: master
Commit: 0f1109ce3613b61bf3c502beb422af8d43ff7b9b
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=0f1109ce3613b61bf3c502beb422af8d43ff7b9b
Author: Tom Stellard <tstellar at gmail.com>
Date: Mon May 31 11:53:23 2010 -0700
r300/compiler: Unroll loops that have a constant number of iterations.
This only works with for loops that increment the counter.
e.g. for(i=0; i<10; i++)
---
.../dri/r300/compiler/radeon_emulate_loops.c | 211 +++++++++++++++++++-
1 files changed, 209 insertions(+), 2 deletions(-)
diff --git a/src/mesa/drivers/dri/r300/compiler/radeon_emulate_loops.c b/src/mesa/drivers/dri/r300/compiler/radeon_emulate_loops.c
index b05ba08..21a9f31 100644
--- a/src/mesa/drivers/dri/r300/compiler/radeon_emulate_loops.c
+++ b/src/mesa/drivers/dri/r300/compiler/radeon_emulate_loops.c
@@ -32,6 +32,7 @@
#include "radeon_emulate_loops.h"
#include "radeon_compiler.h"
+#include "radeon_dataflow.h"
struct emulate_loop_state {
struct radeon_compiler * C;
@@ -45,6 +46,46 @@ struct loop_info {
struct rc_instruction * EndLoop;
};
+struct const_value {
+
+ struct radeon_compiler * C;
+ struct rc_src_register * Src;
+ float Value;
+ int HasValue;
+};
+
+struct count_inst {
+ struct radeon_compiler * C;
+ int Index;
+ rc_swizzle Swz;
+ float Amount;
+ int Unknown;
+};
+
+static float get_constant_value(struct radeon_compiler * c,
+ struct rc_src_register * src,
+ int chan)
+{
+ float base = 1.0f;
+ int swz = GET_SWZ(src->Swizzle, chan);
+ if(swz >= 4 || src->Index >= c->Program.Constants.Count ){
+ rc_error(c, "get_constant_value: Can't find a value.\n");
+ return 0.0f;
+ }
+ if(GET_BIT(src->Negate, chan)){
+ base = -1.0f;
+ }
+ return base *
+ c->Program.Constants.Constants[src->Index].u.Immediate[swz];
+}
+
+static int src_reg_is_immediate(struct rc_src_register * src,
+ struct radeon_compiler * c)
+{
+ return src->File == RC_FILE_CONSTANT &&
+ c->Program.Constants.Constants[src->Index].Type==RC_CONSTANT_IMMEDIATE;
+}
+
static unsigned int loop_count_instructions(struct loop_info * loop)
{
unsigned int count = 0;
@@ -83,6 +124,162 @@ static void loop_unroll(struct emulate_loop_state * s,
}
}
+
+static void update_const_value(void * data, struct rc_instruction * inst,
+ rc_register_file file, unsigned int index, unsigned int mask)
+{
+ struct const_value * value = data;
+ if(value->Src->File != file ||
+ value->Src->Index != index ||
+ !(1 << GET_SWZ(value->Src->Swizzle, 0) & mask)){
+ return;
+ }
+ switch(inst->U.I.Opcode){
+ case RC_OPCODE_MOV:
+ if(!src_reg_is_immediate(&inst->U.I.SrcReg[0], value->C)){
+ return;
+ }
+ value->HasValue = 1;
+ value->Value =
+ get_constant_value(value->C, &inst->U.I.SrcReg[0], 0);
+ break;
+ }
+}
+
+static void get_incr_amount(void * data, struct rc_instruction * inst,
+ rc_register_file file, unsigned int index, unsigned int mask)
+{
+ struct count_inst * count_inst = data;
+ if(file != RC_FILE_TEMPORARY ||
+ count_inst->Index != index ||
+ (1 << GET_SWZ(count_inst->Swz,0) != mask)){
+ return;
+ }
+ switch(inst->U.I.Opcode){
+ int incr_reg;
+ case RC_OPCODE_ADD:
+ {
+ if(inst->U.I.SrcReg[0].File == RC_FILE_TEMPORARY &&
+ inst->U.I.SrcReg[0].Index == count_inst->Index &&
+ inst->U.I.SrcReg[0].Swizzle == count_inst->Swz){
+ incr_reg = 1;
+ } else if( inst->U.I.SrcReg[1].File == RC_FILE_TEMPORARY &&
+ inst->U.I.SrcReg[1].Index == count_inst->Index &&
+ inst->U.I.SrcReg[1].Swizzle == count_inst->Swz){
+ incr_reg = 0;
+ }
+ else{
+ count_inst->Unknown = 1;
+ return;
+ }
+ if(src_reg_is_immediate(&inst->U.I.SrcReg[incr_reg],
+ count_inst->C)){
+ count_inst->Amount = get_constant_value(count_inst->C,
+ &inst->U.I.SrcReg[incr_reg], 0);
+ }
+ else{
+ count_inst->Unknown = 1 ;
+ return;
+ }
+ break;
+ }
+ default:
+ count_inst->Unknown = 1;
+ return;
+ }
+
+}
+
+static int transform_const_loop(struct emulate_loop_state * s,
+ struct loop_info * loop,
+ struct rc_instruction * slt)
+{
+ int end_loops = 1;
+ int iterations;
+ struct count_inst count_inst;
+ float limit_value;
+ struct rc_src_register * counter;
+ struct rc_src_register * limit;
+ struct const_value counter_value;
+ struct rc_instruction * inst;
+
+ /* Find the counter and the upper limit */
+
+ /* limit < counter */
+ if(src_reg_is_immediate(&slt->U.I.SrcReg[0], s->C)){
+ limit = &slt->U.I.SrcReg[0];
+ counter = &slt->U.I.SrcReg[1];
+ }
+ /* counter < limit */
+ else if(src_reg_is_immediate(&slt->U.I.SrcReg[1], s->C)){
+ limit = &slt->U.I.SrcReg[1];
+ counter = &slt->U.I.SrcReg[0];
+ }
+ else{
+ return 0;
+ }
+
+ /* Find the initial value of the counter */
+ counter_value.Src = counter;
+ counter_value.Value = 0.0f;
+ counter_value.HasValue = 0;
+ counter_value.C = s->C;
+ for(inst = s->C->Program.Instructions.Next; inst != loop->BeginLoop;
+ inst = inst->Next){
+ rc_for_all_writes_mask(inst, update_const_value, &counter_value);
+ }
+ if(!counter_value.HasValue){
+ return 0;
+ }
+
+ /* Determine how the counter is modified each loop */
+ count_inst.C = s->C;
+ count_inst.Index = counter->Index;
+ count_inst.Swz = counter->Swizzle;
+ count_inst.Amount = 0.0f;
+ count_inst.Unknown = 0;
+ for(inst = loop->BeginLoop->Next; end_loops > 0; inst = inst->Next){
+ switch(inst->U.I.Opcode){
+ /* XXX In the future we might want to try to unroll nested
+ * loops here.*/
+ case RC_OPCODE_BGNLOOP:
+ end_loops++;
+ break;
+ case RC_OPCODE_ENDLOOP:
+ loop->EndLoop = inst;
+ end_loops--;
+ break;
+ default:
+ rc_for_all_writes_mask(inst, get_incr_amount, &count_inst);
+ if(count_inst.Unknown){
+ return 0;
+ }
+ break;
+ }
+ }
+ if(count_inst.Amount == 0.0f){
+ return 0;
+ }
+
+ /* Calculate the number of iterations of this loop */
+ limit_value = get_constant_value(s->C, limit, 0);
+ iterations = (int) ((limit_value - counter_value.Value) /
+ count_inst.Amount);
+
+ /* Prepare loop for unrolling */
+ /* Remove the first 4 instructions inside the loop, which are part
+ * of the conditional and no longer needed(SGE, IF, BRK, ENDIF).
+ */
+ rc_remove_instruction(loop->BeginLoop->Next);
+ rc_remove_instruction(loop->BeginLoop->Next);
+ rc_remove_instruction(loop->BeginLoop->Next);
+ rc_remove_instruction(loop->BeginLoop->Next);
+
+ loop_unroll(s, loop, iterations);
+ loop->EndLoop = NULL;
+ return 1;
+}
+
/**
* This function prepares a loop to be unrolled by converting it into an if
* statement. Here is an outline of the conversion process:
@@ -94,7 +291,8 @@ static void loop_unroll(struct emulate_loop_state * s,
* <Loop Body> -> ENDIF;
* ENDLOOP; -> ENDLOOP
*
- * @param inst Pointer to a BGNLOOP instruction.
+ * @param inst A pointer to a BGNLOOP instruction.
+ * @return A pointer to the ENDLOOP instruction.
*/
static struct rc_instruction * transform_loop(struct emulate_loop_state * s,
struct rc_instruction * inst)
@@ -107,11 +305,17 @@ static struct rc_instruction * transform_loop(struct emulate_loop_state * s,
loop = &s->Loops[s->LoopCount++];
memset(loop, 0, sizeof(struct loop_info));
-
loop->BeginLoop = inst;
+
/* Reverse the SGE instruction */
ptr = inst->Next;
ptr->U.I.Opcode = RC_OPCODE_SLT;
+
+ /* Check if the number of loops is known at compile time. */
+ if(transform_const_loop(s, loop, ptr)){
+ return loop->BeginLoop->Next;
+ }
+
while(!loop->EndLoop){
struct rc_instruction * endif;
if(ptr->Type == RC_INSTRUCTION_NORMAL){
@@ -160,6 +364,9 @@ static void rc_unroll_loops(struct emulate_loop_state *s,
* loops are unrolled first.
*/
for( i = s->LoopCount - 1; i >= 0; i-- ){
+ if(!s->Loops[i].EndLoop){
+ continue;
+ }
unsigned int iterations = loop_calc_iterations(&s->Loops[i],
s->LoopCount, max_instructions);
loop_unroll(s, &s->Loops[i], iterations);
More information about the mesa-commit
mailing list