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

diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index c77ae1b7a7933f84ada8008ff1e8c118e19d86a0..7a8ca63ce766e275f43beb189f551ea0f7eb6db9 100644 (file)
--- 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 c621726a03f0aa9521ccfb3553c887071a3525e6..35b8e14ddc6126d4d8e25be00bc5bb51c604a997 100644 (file)
--- 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;
       }