From: Matthias Braun <matze@braunis.de>
Date: Mon, 12 Jun 2017 20:30:52 +0000 (+0000)
Subject: SplitKit: Fix partially live subreg splitting
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=c37ab5f8054f2333e6dbcf819c1457abecba0f64;p=llvm

SplitKit: Fix partially live subreg splitting

Fix thinko/typo in subreg aware liverange splitting logic. I'm not sure
how to write a proper testcase for this. The original problem only
happens on an out-of-tree target. Forcing subreg enabled targets to
spill and split in a predictable way is near impossible.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@305228 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SplitKit.cpp b/lib/CodeGen/SplitKit.cpp
index 3a50aaa6998..008b984dd96 100644
--- a/lib/CodeGen/SplitKit.cpp
+++ b/lib/CodeGen/SplitKit.cpp
@@ -569,8 +569,7 @@ SlotIndex SplitEditor::buildCopy(unsigned FromReg, unsigned ToReg,
 
   // Greedy heuristic: Keep iterating keeping the best covering subreg index
   // each time.
-  LaneBitmask LanesLeft =
-      LaneMask & ~(TRI.getSubRegIndexLaneMask(BestCover));
+  LaneBitmask LanesLeft = LaneMask & ~(TRI.getSubRegIndexLaneMask(BestIdx));
   while (LanesLeft.any()) {
     unsigned BestIdx = 0;
     int BestCover = INT_MIN;