freedreno/ir3: cleanup "partially const" ubo srcs

Move the constant part of the indirect offset into nir intrinsic base.
When we have multiple indirect accesses with different constant offsets,
this lets other opt passes clean up things to use a single address
register value.

Signed-off-by: Rob Clark <[email protected]>
Reviewed-by: Eric Anholt <[email protected]>

1 files changed, 52 insertions, 4 deletions

diff --git a/src/freedreno/ir3/ir3_nir_analyze_ubo_ranges.c b/src/freedreno/ir3/ir3_nir_analyze_ubo_ranges.c
index 06c1c2212f2..abe8d20da30 100644
--- a/src/freedreno/ir3/ir3_nir_analyze_ubo_ranges.c
+++ b/src/freedreno/ir3/ir3_nir_analyze_ubo_ranges.c
@@ -74,6 +74,41 @@ gather_ubo_ranges(nir_shader *nir, nir_intrinsic_instr *instr,
 		state->range[block].end = r.end;
 }
 
+/* For indirect offset, it is common to see a pattern of multiple
+ * loads with the same base, but different constant offset, ie:
+ *
+ *    vec1 32 ssa_33 = iadd ssa_base, const_offset
+ *    vec4 32 ssa_34 = intrinsic load_uniform (ssa_33) (base=N, 0, 0)
+ *
+ * Detect this, and peel out the const_offset part, to end up with:
+ *
+ *    vec4 32 ssa_34 = intrinsic load_uniform (ssa_base) (base=N+const_offset, 0, 0)
+ *
+ * This gives the other opt passes something much easier to work
+ * with (ie. not requiring value range tracking)
+ */
+static void
+handle_partial_const(nir_ssa_def **srcp, unsigned *offp)
+{
+	if ((*srcp)->parent_instr->type != nir_instr_type_alu)
+		return;
+
+	nir_alu_instr *alu = nir_instr_as_alu((*srcp)->parent_instr);
+	if (alu->op != nir_op_iadd)
+		return;
+
+	if (!(alu->src[0].src.is_ssa && alu->src[1].src.is_ssa))
+		return;
+
+	if (nir_src_is_const(alu->src[0].src)) {
+		*offp += nir_src_as_uint(alu->src[0].src);
+		*srcp = alu->src[1].src.ssa;
+	} else if (nir_src_is_const(alu->src[1].src)) {
+		*srcp = alu->src[0].src.ssa;
+		*offp += nir_src_as_uint(alu->src[1].src);
+	}
+}
+
 static void
 lower_ubo_load_to_uniform(nir_intrinsic_instr *instr, nir_builder *b,
 						  struct ir3_ubo_analysis_state *state)
@@ -107,21 +142,34 @@ lower_ubo_load_to_uniform(nir_intrinsic_instr *instr, nir_builder *b,
 	b->cursor = nir_before_instr(&instr->instr);
 
 	nir_ssa_def *ubo_offset = nir_ssa_for_src(b, instr->src[1], 1);
+	unsigned const_offset = 0;
+
+	handle_partial_const(&ubo_offset, &const_offset);
+
+	/* UBO offset is in bytes, but uniform offset is in units of
+	 * dwords, so we need to divide by 4 (right-shift by 2).  And
+	 * also the same for the constant part of the offset:
+	 */
 	nir_ssa_def *new_offset = ir3_nir_try_propagate_bit_shift(b, ubo_offset, -2);
-	nir_ssa_def *uniform_offset;
-	if (new_offset)
+	nir_ssa_def *uniform_offset = NULL;
+	if (new_offset) {
 		uniform_offset = new_offset;
-	else
+	} else {
 		uniform_offset = nir_ushr(b, ubo_offset, nir_imm_int(b, 2));
+	}
+
+	debug_assert(!(const_offset & 0x3));
+	const_offset >>= 2;
 
 	const int range_offset =
 		(state->range[block].offset - state->range[block].start) / 4;
+	const_offset += range_offset;
 
 	nir_intrinsic_instr *uniform =
 		nir_intrinsic_instr_create(b->shader, nir_intrinsic_load_uniform);
 	uniform->num_components = instr->num_components;
 	uniform->src[0] = nir_src_for_ssa(uniform_offset);
-	nir_intrinsic_set_base(uniform, range_offset);
+	nir_intrinsic_set_base(uniform, const_offset);
 	nir_ssa_dest_init(&uniform->instr, &uniform->dest,
 					  uniform->num_components, instr->dest.ssa.bit_size,
 					  instr->dest.ssa.name);