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

1 files changed, 0 insertions, 7 deletions

diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index c77ae1b7a7..7a8ca63ce7 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);
   }
 }