r300/compiler: Fix regression in pair scheduling

Signed-off-by: Nicolai Hähnle <nhaehnle@gmail.com>

diff --git a/src/mesa/drivers/dri/r300/compiler/radeon_pair_schedule.c b/src/mesa/drivers/dri/r300/compiler/radeon_pair_schedule.c
index ea01bb78819ac067cb3cc897b1e6b4c8a1e0703f..df67aafe02884e739f376e3e2e48ef1a9bd85770 100644 (file)
--- a/src/mesa/drivers/dri/r300/compiler/radeon_pair_schedule.c
+++ b/src/mesa/drivers/dri/r300/compiler/radeon_pair_schedule.c
@@ -179,8 +179,19 @@ static void commit_instruction(struct schedule_state * s, struct schedule_instru
 
        for(unsigned int i = 0; i < sinst->NumWriteValues; ++i) {
                struct reg_value * v = sinst->WriteValues[i];
-               for(struct reg_value_reader * r = v->Readers; r; r = r->Next) {
-                       decrease_dependencies(s, r->Reader);
+               if (v->NumReaders) {
+                       for(struct reg_value_reader * r = v->Readers; r; r = r->Next) {
+                               decrease_dependencies(s, r->Reader);
+                       }
+               } else {
+                       /* This happens in instruction sequences of the type
+                        *  OP r.x, ...;
+                        *  OP r.x, r.x, ...;
+                        * See also the subtlety in how instructions that both
+                        * read and write the same register are scanned.
+                        */
+                       if (v->Next)
+                               decrease_dependencies(s, v->Next->Writer);
                }
        }
 }
@@ -360,6 +371,13 @@ static void scan_read(void * data, struct rc_instruction * inst,
        if (!v)
                return;
 
+       if (v->Writer == s->Current) {
+               /* The instruction reads and writes to a register component.
+                * In this case, we only want to increment dependencies by one.
+                */
+               return;
+       }
+
        DBG("%i: read %i[%i] chan %i\n", s->Current->Instruction->IP, file, index, chan);
 
        struct reg_value_reader * reader = memory_pool_malloc(&s->C->Pool, sizeof(*reader));
@@ -426,8 +444,12 @@ static void schedule_block(struct r300_fragment_program_compiler * c,
 
                DBG("%i: Scanning\n", inst->IP);
 
-               rc_for_all_reads(inst, &scan_read, &s);
+               /* The order of things here is subtle and maybe slightly
+                * counter-intuitive, to account for the case where an
+                * instruction writes to the same register as it reads
+                * from. */
                rc_for_all_writes(inst, &scan_write, &s);
+               rc_for_all_reads(inst, &scan_read, &s);
 
                DBG("%i: Has %i dependencies\n", inst->IP, s.Current->NumDependencies);