LiveRegMatrix: Fix some subreg interference checks

Surprisingly, one of the three interference checks in LiveRegMatrix was
using the main live range instead of the apropriate subregister range
resulting in unnecessarily conservative results.

llvm-svn: 296722

1 files changed, 8 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/LiveRegMatrix.cpp b/llvm/lib/CodeGen/LiveRegMatrix.cpp
index 596d78763b1..882de1a3fad 100644
--- a/llvm/lib/CodeGen/LiveRegMatrix.cpp
+++ b/llvm/lib/CodeGen/LiveRegMatrix.cpp
@@ -175,10 +175,10 @@ bool LiveRegMatrix::checkRegUnitInterference(LiveInterval &VirtReg,
   return Result;
 }
 
-LiveIntervalUnion::Query &LiveRegMatrix::query(LiveInterval &VirtReg,
+LiveIntervalUnion::Query &LiveRegMatrix::query(const LiveRange &LR,
                                                unsigned RegUnit) {
   LiveIntervalUnion::Query &Q = Queries[RegUnit];
-  Q.init(UserTag, VirtReg, Matrix[RegUnit]);
+  Q.init(UserTag, LR, Matrix[RegUnit]);
   return Q;
 }
 
@@ -196,9 +196,12 @@ LiveRegMatrix::checkInterference(LiveInterval &VirtReg, unsigned PhysReg) {
     return IK_RegUnit;
 
   // Check the matrix for virtual register interference.
-  for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units)
-    if (query(VirtReg, *Units).checkInterference())
-      return IK_VirtReg;
+  bool Interference = foreachUnit(TRI, VirtReg, PhysReg,
+                                  [&](unsigned Unit, const LiveRange &LR) {
+    return query(LR, Unit).checkInterference();
+  });
+  if (Interference)
+    return IK_VirtReg;
 
   return IK_Free;
 }