From e13ff5be315820ac593656788f6b1060ba1032fc Mon Sep 17 00:00:00 2001
From: David Given <dg@cowlark.com>
Date: Tue, 4 Oct 2016 21:29:03 +0200
Subject: [PATCH] Don't allocate new vregs for REG and NOP --- a bit hacky, but
 suppresses stray movs very effectively.

---
 mach/proto/mcg/pass_instructionselection.c | 18 +++++++++++++++++-
 mach/proto/mcg/table                       |  2 --
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/mach/proto/mcg/pass_instructionselection.c b/mach/proto/mcg/pass_instructionselection.c
index 20a93c697..48ede30df 100644
--- a/mach/proto/mcg/pass_instructionselection.c
+++ b/mach/proto/mcg/pass_instructionselection.c
@@ -129,8 +129,24 @@ static struct insn* walk_instructions(struct burm_node* node, int goal)
 
         if (!insn->insndata->is_fragment)
         {
+            struct vreg* vreg = NULL;
+
+            switch (node->label)
+            {
+                case ir_to_esn(IR_REG, 0):
+                    vreg = node->ir->result;
+                    break;
+
+                case ir_to_esn(IR_NOP, 0):
+                    vreg = node->left->ir->result;
+                    break;
+
+                default:
+                    vreg = new_vreg();
+            }
+
             insn->hop = current_hop = new_hop(0, insn->ir);
-            insn->hop->output = new_vreg();
+            insn->hop->output = vreg;
             emit(insn);
             hop_print('I', current_hop);
 
diff --git a/mach/proto/mcg/table b/mach/proto/mcg/table
index 0fa07b6bc..4d892c069 100644
--- a/mach/proto/mcg/table
+++ b/mach/proto/mcg/table
@@ -69,11 +69,9 @@ PATTERNS
 		cost 4;
 
 	reg = in:REG
-		emit "mov %reg, %in"
 		cost 1;
 
 	reg = NOP(in:reg)
-		emit "mov %reg, %in"
 		cost 1;