From: Jakob Stoklund Olesen <stoklund@2pi.dk>
Date: Wed, 4 May 2011 23:59:00 +0000 (+0000)
Subject: Disable physical register coalescing by default.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=7a2718a3c185dc4b52d04ac701a0abe173b2e273;p=oota-llvm.git

Disable physical register coalescing by default.

Joining physregs is inherently dangerous because it uses a heuristic to avoid
creating invalid code. Linear scan had an emergency spilling mechanism to deal
with those rare cases. The new greedy allocator does not.

The greedy register allocator is much better at taking hints, so this has almost
no impact on code size and quality. The few cases where it matters show up as
unit tests that now have -join-physregs enabled explicitly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130896 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 44333315559..cebf4c9f4a5 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -63,7 +63,7 @@ DisableCrossClassJoin("disable-cross-class-join",
 static cl::opt<bool>
 EnablePhysicalJoin("join-physregs",
                    cl::desc("Join physical register copies"),
-                   cl::init(true), cl::Hidden);
+                   cl::init(false), cl::Hidden);
 
 static cl::opt<bool>
 VerifyCoalescing("verify-coalescing",