From 9c39690edfc901d1ab7cc5726088879d0113684a Mon Sep 17 00:00:00 2001
From: Jakob Stoklund Olesen <stoklund@2pi.dk>
Date: Tue, 31 Aug 2010 01:27:49 +0000
Subject: [PATCH] Add experimental -disable-physical-join command line option.

Eventually, we want to disable physreg coalescing completely, and let the
register allocator do its job using hints.

This option makes it possible to measure the impact of disabling physreg
coalescing.

llvm-svn: 112567
---
 llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 34c484103cfc..5dd5fdb7b159 100644
--- a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -59,6 +59,11 @@ DisableCrossClassJoin("disable-cross-class-join",
                cl::desc("Avoid coalescing cross register class copies"),
                cl::init(false), cl::Hidden);
 
+static cl::opt<bool>
+DisablePhysicalJoin("disable-physical-join",
+               cl::desc("Avoid coalescing physical register copies"),
+               cl::init(false), cl::Hidden);
+
 INITIALIZE_AG_PASS(SimpleRegisterCoalescing, RegisterCoalescer,
                 "simple-register-coalescing", "Simple Register Coalescing", 
                 false, false, true);
@@ -1036,6 +1041,11 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
     return false;  // Not coalescable.
   }
 
+  if (DisablePhysicalJoin && CP.isPhys()) {
+    DEBUG(dbgs() << "\tPhysical joins disabled.\n");
+    return false;
+  }
+
   DEBUG(dbgs() << "\tConsidering merging %reg" << CP.getSrcReg());
 
   // Enforce policies.