Don't add live ranges for sub-registers when clobbering a physical register.

Both coalescing and register allocation already check aliases for interference,
so these extra segments are only slowing us down.

This speeds up both linear scan and the greedy register allocator.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129283 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 7 insertions, 15 deletions

diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index c77ae1b..7a8ca63 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -578,13 +578,6 @@ void LiveIntervals::handleRegisterDef(MachineBasicBlock *MBB,
       CopyMI = MI;
     handlePhysicalRegisterDef(MBB, MI, MIIdx, MO,
                               getOrCreateInterval(MO.getReg()), CopyMI);
-    // Def of a register also defines its sub-registers.
-    for (const unsigned* AS = tri_->getSubRegisters(MO.getReg()); *AS; ++AS)
-      // If MI also modifies the sub-register explicitly, avoid processing it
-      // more than once. Do not pass in TRI here so it checks for exact match.
-      if (!MI->definesRegister(*AS))
-        handlePhysicalRegisterDef(MBB, MI, MIIdx, MO,
-                                  getOrCreateInterval(*AS), 0);
   }
 }
 
diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index c621726..35b8e14 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -208,15 +208,14 @@ bool SimpleRegisterCoalescing::AdjustCopiesBackFrom(const CoalescerPair &CP,
   if (ValLR+1 != BLR) return false;
 
   // If a live interval is a physical register, conservatively check if any
-  // of its sub-registers is overlapping the live interval of the virtual
-  // register. If so, do not coalesce.
-  if (TargetRegisterInfo::isPhysicalRegister(IntB.reg) &&
-      *tri_->getSubRegisters(IntB.reg)) {
-    for (const unsigned* SR = tri_->getSubRegisters(IntB.reg); *SR; ++SR)
-      if (li_->hasInterval(*SR) && IntA.overlaps(li_->getInterval(*SR))) {
+  // of its aliases is overlapping the live interval of the virtual register.
+  // If so, do not coalesce.
+  if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) {
+    for (const unsigned *AS = tri_->getAliasSet(IntB.reg); *AS; ++AS)
+      if (li_->hasInterval(*AS) && IntA.overlaps(li_->getInterval(*AS))) {
         DEBUG({
-            dbgs() << "\t\tInterfere with sub-register ";
-            li_->getInterval(*SR).print(dbgs(), tri_);
+            dbgs() << "\t\tInterfere with alias ";
+            li_->getInterval(*AS).print(dbgs(), tri_);
           });
         return false;
       }