i965: Add support for register spilling.

It can be tested with if (0) replaced with if (1) to force spilling for all
virtual GRFs.  Some simple tests work, but large texturing tests fail.

1 files changed, 67 insertions, 6 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index bc39d1c29a..f38976aa8a 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -179,10 +179,6 @@ type_size(const struct glsl_type *type)
    }
 }
 
-static const fs_reg reg_undef;
-static const fs_reg reg_null_f(ARF, BRW_ARF_NULL, BRW_REGISTER_TYPE_F);
-static const fs_reg reg_null_d(ARF, BRW_ARF_NULL, BRW_REGISTER_TYPE_D);
-
 int
 fs_visitor::virtual_grf_alloc(int size)
 {
@@ -2227,6 +2223,47 @@ fs_visitor::generate_discard_and(fs_inst *inst, struct brw_reg mask)
 }
 
 void
+fs_visitor::generate_spill(fs_inst *inst, struct brw_reg src)
+{
+   assert(inst->mlen != 0);
+
+   brw_MOV(p,
+	   retype(brw_message_reg(inst->base_mrf + 1), BRW_REGISTER_TYPE_UD),
+	   retype(src, BRW_REGISTER_TYPE_UD));
+   brw_oword_block_write(p, brw_message_reg(inst->base_mrf), 1, inst->offset);
+}
+
+void
+fs_visitor::generate_unspill(fs_inst *inst, struct brw_reg dst)
+{
+   assert(inst->mlen != 0);
+
+   /* Clear any post destination dependencies that would be ignored by
+    * the block read.  See the B-Spec for pre-gen5 send instruction.
+    *
+    * This could use a better solution, since texture sampling and
+    * math reads could potentially run into it as well -- anywhere
+    * that we have a SEND with a destination that is a register that
+    * was written but not read within the last N instructions (what's
+    * N?  unsure).  This is rare because of dead code elimination, but
+    * not impossible.
+    */
+   if (intel->gen == 4 && !intel->is_g4x)
+      brw_MOV(p, brw_null_reg(), dst);
+
+   brw_oword_block_read(p, dst, brw_message_reg(inst->base_mrf), 1,
+			inst->offset);
+
+   if (intel->gen == 4 && !intel->is_g4x) {
+      /* gen4 errata: destination from a send can't be used as a
+       * destination until it's been read.  Just read it so we don't
+       * have to worry.
+       */
+      brw_MOV(p, brw_null_reg(), dst);
+   }
+}
+
+void
 fs_visitor::assign_curb_setup()
 {
    c->prog_data.first_curbe_grf = c->key.nr_payload_regs;
@@ -3040,6 +3077,15 @@ fs_visitor::generate_code()
       case FS_OPCODE_DDY:
 	 generate_ddy(inst, dst, src[0]);
 	 break;
+
+      case FS_OPCODE_SPILL:
+	 generate_spill(inst, src[0]);
+	 break;
+
+      case FS_OPCODE_UNSPILL:
+	 generate_unspill(inst, dst);
+	 break;
+
       case FS_OPCODE_FB_WRITE:
 	 generate_fb_write(inst);
 	 break;
@@ -3145,10 +3191,25 @@ brw_wm_fs_emit(struct brw_context *brw, struct brw_wm_compile *c)
 	 progress = v.dead_code_eliminate() || progress;
       } while (progress);
 
+      if (0) {
+	 /* Debug of register spilling: Go spill everything. */
+	 int virtual_grf_count = v.virtual_grf_next;
+	 for (int i = 1; i < virtual_grf_count; i++) {
+	    v.spill_reg(i);
+	 }
+	 v.calculate_live_intervals();
+      }
+
       if (0)
 	 v.assign_regs_trivial();
-      else
-	 v.assign_regs();
+      else {
+	 while (!v.assign_regs()) {
+	    if (v.fail)
+	       break;
+
+	    v.calculate_live_intervals();
+	 }
+      }
    }
 
    if (!v.fail)