mesa: Do copy propagation across if-else-endif.

Addresses excessive TEMP allocation in vertex shaders where all CONSTs are
stored into TEMPS at the start, but copy propagation was failing due to
the presence of IFs.

We could do something about loops, but ifs are easy enough.

1 files changed, 28 insertions, 2 deletions

diff --git a/src/mesa/program/ir_to_mesa.cpp b/src/mesa/program/ir_to_mesa.cpp
index 7f905ae5ce..33c262f8ca 100644
--- a/src/mesa/program/ir_to_mesa.cpp
+++ b/src/mesa/program/ir_to_mesa.cpp
@@ -2670,6 +2670,8 @@ ir_to_mesa_visitor::copy_propagate(void)
    ir_to_mesa_instruction **acp = rzalloc_array(mem_ctx,
 						    ir_to_mesa_instruction *,
 						    this->next_temp * 4);
+   int *acp_level = rzalloc_array(mem_ctx, int, this->next_temp * 4);
+   int level = 0;
 
    foreach_iter(exec_list_iterator, iter, this->instructions) {
       ir_to_mesa_instruction *inst = (ir_to_mesa_instruction *)iter.get();
@@ -2700,6 +2702,8 @@ ir_to_mesa_visitor::copy_propagate(void)
 	       break;
 	    }
 
+	    assert(acp_level[acp_base + src_chan] <= level);
+
 	    if (!first) {
 	       first = copy_chan;
 	    } else {
@@ -2732,12 +2736,32 @@ ir_to_mesa_visitor::copy_propagate(void)
       switch (inst->op) {
       case OPCODE_BGNLOOP:
       case OPCODE_ENDLOOP:
-      case OPCODE_ELSE:
-      case OPCODE_ENDIF:
 	 /* End of a basic block, clear the ACP entirely. */
 	 memset(acp, 0, sizeof(*acp) * this->next_temp * 4);
 	 break;
 
+      case OPCODE_IF:
+	 ++level;
+	 break;
+
+      case OPCODE_ENDIF:
+      case 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 == OPCODE_ENDIF)
+	    --level;
+	 break;
+
       default:
 	 /* Continuing the block, clear any written channels from
 	  * the ACP.
@@ -2802,11 +2826,13 @@ ir_to_mesa_visitor::copy_propagate(void)
 	 for (int i = 0; i < 4; i++) {
 	    if (inst->dst_reg.writemask & (1 << i)) {
 	       acp[4 * inst->dst_reg.index + i] = inst;
+	       acp_level[4 * inst->dst_reg.index + i] = level;
 	    }
 	 }
       }
    }
 
+   ralloc_free(acp_level);
    ralloc_free(acp);
 }