freedreno/ir3: avoid fan-in sources referring to same instruction

Since the RA has to be done s.t. each one gets its own (adjacent)
register, it would complicate matters if instructions were allowed to be
repeated. This enables copy-propagation use in situations where
previously that might have happened.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Rob Clark <robclark@freedesktop.org>

diff --git a/src/gallium/drivers/freedreno/ir3/ir3_cp.c b/src/gallium/drivers/freedreno/ir3/ir3_cp.c
index 73c2a27c6eb6f4cc3db07ea36aec51ed03f8bf8f..83bcb7a742bda6605f0e6d71867badbaae9c75e6 100644 (file)
--- a/src/gallium/drivers/freedreno/ir3/ir3_cp.c
+++ b/src/gallium/drivers/freedreno/ir3/ir3_cp.c
@@ -70,7 +70,7 @@ static void walk_children(struct ir3_instruction *instr, bool keep)
 static struct ir3_instruction *
 instr_cp_fanin(struct ir3_instruction *instr)
 {
-       unsigned i;
+       unsigned i, j;
 
        /* we need to handle fanin specially, to detect cases
         * when we need to keep a mov
@@ -92,7 +92,15 @@ instr_cp_fanin(struct ir3_instruction *instr)
                        if (is_meta(cand) && (cand->opc == OPC_META_FO))
                                cand = instr_cp(src->instr, true);
 
-                       src->instr = cand;
+                       /* we can't have 2 registers referring to the same instruction, so
+                        * go through and check if any already refer to the candidate
+                        * instruction. if so, don't do the propagation.
+                        */
+                       for (j = 1; j < instr->regs_count; j++)
+                               if (instr->regs[j]->instr == cand)
+                                       break;
+                       if (j == instr->regs_count)
+                               src->instr = cand;
                }
        }