From: Evan Cheng <evan.cheng@apple.com>
Date: Fri, 23 Jan 2009 05:48:59 +0000 (+0000)
Subject: Only check if coalescing is worthwhile when the result is targeting a more restrictiv... 
X-Git-Tag: android-x86-6.0-r1~1003^2~23050
X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=c16d37ead0f07cc250d06e5cdbb3836f2f6082cd;p=android-x86%2Fexternal-llvm.git

Only check if coalescing is worthwhile when the result is targeting a more restrictive register class.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62837 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index f0b0d58d135..f3ffc69cccb 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -1290,8 +1290,13 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
       }
     }
 
+    // If we are joining two virtual registers and the resulting register
+    // class is more restrictive (fewer register, smaller size). Check if it's
+    // worth doing the merge.
     if (!SrcIsPhys && !DstIsPhys &&
-        !isWinToJoinCrossClass(LargeReg, SmallReg, Limit)) {
+        (isExtSubReg || DstRC->isASubClass()) &&
+        !isWinToJoinCrossClass(LargeReg, SmallReg,
+                               allocatableRCRegs_[NewRC].count())) {
       DOUT << "\tSrc/Dest are different register classes.\n";
       // Allow the coalescer to try again in case either side gets coalesced to
       // a physical register that's compatible with the other side. e.g.