From: Matt Turner <mattst88@gmail.com>
Date: Sun, 30 Mar 2014 19:41:55 +0000 (-0700)
Subject: i965/fs: Perform CSE on load_payload instructions if it's not a copy.
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=31ae9c25ff07681f59e6ffc53c039e842cb39464;p=mesa.git

i965/fs: Perform CSE on load_payload instructions if it's not a copy.

Since CSE creates instructions, if we let CSE generate things register
coalescing can't remove, bad things will happen. Only let CSE combine
non-copy load_payloads.

E.g., allow CSE to handle this

   load_payload vgrf4+0, vgrf5, vgrf6

but not this

   load_payload vgrf4+0, vgrf5+0, vgrf5+1
---

diff --git a/src/mesa/drivers/dri/i965/brw_fs_cse.cpp b/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
index abaf6880040..a319307a4c3 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
@@ -42,6 +42,22 @@ struct aeb_entry : public exec_node {
 };
 }
 
+static bool
+is_copy_payload(const fs_inst *inst)
+{
+   const int reg = inst->src[0].reg;
+   if (inst->src[0].reg_offset != 0)
+      return false;
+
+   for (int i = 1; i < inst->sources; i++) {
+      if (inst->src[i].reg != reg ||
+          inst->src[i].reg_offset != i) {
+         return false;
+      }
+   }
+   return true;
+}
+
 static bool
 is_expression(const fs_inst *const inst)
 {
@@ -84,6 +100,8 @@ is_expression(const fs_inst *const inst)
    case SHADER_OPCODE_SIN:
    case SHADER_OPCODE_COS:
       return inst->mlen == 0;
+   case SHADER_OPCODE_LOAD_PAYLOAD:
+      return !is_copy_payload(inst);
    default:
       return false;
    }