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-rw-r--r--src/mesa/drivers/dri/i965/brw_fs.cpp90
1 files changed, 90 insertions, 0 deletions
diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index 472e6d06f6..5eaa998447 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -455,6 +455,7 @@ public:
void assign_regs();
void assign_regs_trivial();
void calculate_live_intervals();
+ bool propagate_constants();
bool dead_code_eliminate();
bool virtual_grf_interferes(int a, int b);
void generate_code();
@@ -2523,6 +2524,94 @@ fs_visitor::calculate_live_intervals()
}
/**
+ * Attempts to move immediate constants into the immediate
+ * constant slot of following instructions.
+ *
+ * Immediate constants are a bit tricky -- they have to be in the last
+ * operand slot, you can't do abs/negate on them,
+ */
+
+bool
+fs_visitor::propagate_constants()
+{
+ bool progress = false;
+
+ return false;
+
+ foreach_iter(exec_list_iterator, iter, this->instructions) {
+ fs_inst *inst = (fs_inst *)iter.get();
+
+ if (inst->opcode != BRW_OPCODE_MOV ||
+ inst->predicated ||
+ inst->dst.file != GRF || inst->src[0].file != IMM ||
+ inst->dst.type != inst->src[0].type)
+ continue;
+
+ /* Don't bother with cases where we should have had the
+ * operation on the constant folded in GLSL already.
+ */
+ if (inst->saturate)
+ continue;
+
+ /* Found a move of a constant to a GRF. Find anything else using the GRF
+ * before it's written, and replace it with the constant if we can.
+ */
+ exec_list_iterator scan_iter = iter;
+ scan_iter.next();
+ for (; scan_iter.has_next(); scan_iter.next()) {
+ fs_inst *scan_inst = (fs_inst *)scan_iter.get();
+
+ if (scan_inst->opcode == BRW_OPCODE_DO ||
+ scan_inst->opcode == BRW_OPCODE_WHILE ||
+ scan_inst->opcode == BRW_OPCODE_ELSE ||
+ scan_inst->opcode == BRW_OPCODE_ENDIF) {
+ break;
+ }
+
+ for (int i = 2; i >= 0; i--) {
+ if (scan_inst->src[i].file != GRF ||
+ scan_inst->src[i].reg != inst->dst.reg ||
+ scan_inst->src[i].reg_offset != inst->dst.reg_offset)
+ continue;
+
+ /* Don't bother with cases where we should have had the
+ * operation on the constant folded in GLSL already.
+ */
+ if (scan_inst->src[i].negate || scan_inst->src[i].abs)
+ continue;
+
+ switch (scan_inst->opcode) {
+ case BRW_OPCODE_MOV:
+ scan_inst->src[i] = inst->src[0];
+ progress = true;
+ break;
+
+ case BRW_OPCODE_MUL:
+ case BRW_OPCODE_ADD:
+ if (i == 1) {
+ scan_inst->src[i] = inst->src[0];
+ progress = true;
+ } else if (i == 0 && scan_inst->src[1].file != IMM) {
+ /* Fit this constant in by commuting the operands */
+ scan_inst->src[0] = scan_inst->src[1];
+ scan_inst->src[1] = inst->src[0];
+ }
+ break;
+ }
+ }
+
+ if (scan_inst->dst.file == GRF &&
+ scan_inst->dst.reg == inst->dst.reg &&
+ (scan_inst->dst.reg_offset == inst->dst.reg_offset ||
+ scan_inst->opcode == FS_OPCODE_TEX)) {
+ break;
+ }
+ }
+ }
+
+ return progress;
+}
+/**
* Must be called after calculate_live_intervales() to remove unused
* writes to registers -- register allocation will fail otherwise
* because something deffed but not used won't be considered to
@@ -2876,6 +2965,7 @@ brw_wm_fs_emit(struct brw_context *brw, struct brw_wm_compile *c)
progress = false;
v.calculate_live_intervals();
+ progress = v.propagate_constants() || progress;
progress = v.dead_code_eliminate() || progress;
} while (progress);