freedreno/ir3: handle "holes" in inputs

If, for example, only the x/y/w components of in.xyzw are actually used,
we still need to have a group of four registers and assign all four
components.  The hardware can't write in.xy and in.w to discontiguous
registers.  To handle this, pad with a dummy NOP instruction, to keep
the neighbor chain contiguous.

This fixes a problem noticed with firefox OMTC.

Signed-off-by: Rob Clark <robclark@freedesktop.org>

diff --git a/src/gallium/drivers/freedreno/ir3/ir3_group.c b/src/gallium/drivers/freedreno/ir3/ir3_group.c
index f215c1c..da2142e 100644 (file)
--- a/src/gallium/drivers/freedreno/ir3/ir3_group.c
+++ b/src/gallium/drivers/freedreno/ir3/ir3_group.c
@@ -187,6 +187,36 @@ static void instr_find_neighbors(struct ir3_instruction *instr)
        }
 }
 
+/* a bit of sadness.. we can't have "holes" in inputs from PoV of
+ * register assignment, they still need to be grouped together.  So
+ * we need to insert dummy/padding instruction for grouping, and
+ * then take it back out again before anyone notices.
+ */
+static void pad_and_group_input(struct ir3_instruction **input, unsigned n)
+{
+       int i, mask = 0;
+       struct ir3_block *block = NULL;
+
+       for (i = n - 1; i >= 0; i--) {
+               struct ir3_instruction *instr = input[i];
+               if (instr) {
+                       block = instr->block;
+               } else if (block) {
+                       instr = ir3_instr_create(block, 0, OPC_NOP);
+                       ir3_reg_create(instr, 0, IR3_REG_SSA);    /* dst */
+                       input[i] = instr;
+                       mask |= (1 << i);
+               }
+       }
+
+       group_n(&arr_ops_in, input, n);
+
+       for (i = 0; i < n; i++) {
+               if (mask & (1 << i))
+                       input[i] = NULL;
+       }
+}
+
 static void block_find_neighbors(struct ir3_block *block)
 {
        unsigned i;
@@ -214,7 +244,7 @@ static void block_find_neighbors(struct ir3_block *block)
                 * on vec4 boundaries
                 */
                for (i = 0; i < block->ninputs; i += 4)
-                       group_n(&arr_ops_in, &block->inputs[i], 4);
+                       pad_and_group_input(&block->inputs[i], 4);
                for (i = 0; i < block->noutputs; i += 4)
                        group_n(&arr_ops_out, &block->outputs[i], 4);