From: Evan Cheng <evan.cheng@apple.com>
Date: Mon, 18 Feb 2008 18:56:31 +0000 (+0000)
Subject: - Remove the previous check which broke coalescer-commute3.ll
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=a9407f593778c3eff02dbb1fa11129865a59c6d3;p=oota-llvm.git

- Remove the previous check which broke coalescer-commute3.ll
- For now, conservatively ignore copy MI whose source is a physical register. Commuting its def MI can cause a physical register live interval to be live through a loop (since we know it's live coming into the def MI).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47281 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 199c89ef55a..7c512ed368a 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -247,11 +247,11 @@ bool SimpleRegisterCoalescing::RemoveCopyByCommutingDef(LiveInterval &IntA,
 
   unsigned CopyIdx = li_->getDefIndex(li_->getInstructionIndex(CopyMI));
 
-  // FIXME: For now, only eliminate the copy by commuting its def is the source
-  // does not live pass the move. Coalescing those copies may end up may simply
-  // end up swapping a live interval for another. That and because usually only
-  // the non-two address operand can be folded can end up pessimizing the code.
-  if (CopyMI->findRegisterUseOperandIdx(IntA.reg, true) != -1)
+  // FIXME: For now, only eliminate the copy by commuting its def when the
+  // source register is a virtual register. We want to guard against cases
+  // where the copy is a back edge copy and commuting the def lengthen the
+  // live interval of the source register to the entire loop.
+  if (TargetRegisterInfo::isPhysicalRegister(IntA.reg))
     return false;
 
   // BValNo is a value number in B that is defined by a copy from A. 'B3' in