Fix an exotic bug that only showed up in an internal test case.

SimpleRegisterCoalescing::JoinIntervals() uses CoalescerPair to determine if a
copy is coalescable, and in very rare cases it can return true where LHS is not
live - the coalescable copy can come from an alias of the physreg in LHS.

llvm-svn: 106021

1 files changed, 4 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 16d929bbfa3..6f3fc99a0ca 100644
--- a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -2310,7 +2310,8 @@ SimpleRegisterCoalescing::JoinIntervals(LiveInterval &LHS, LiveInterval &RHS,
 
       // Figure out the value # from the RHS.
       LiveRange *lr = RHS.getLiveRangeContaining(VNI->def.getPrevSlot());
-      assert(lr && "Cannot find live range");
+      // The copy could be to an aliased physreg.
+      if (!lr) continue;
       LHSValsDefinedFromRHS[VNI] = lr->valno;
     }
 
@@ -2329,7 +2330,8 @@ SimpleRegisterCoalescing::JoinIntervals(LiveInterval &LHS, LiveInterval &RHS,
 
       // Figure out the value # from the LHS.
       LiveRange *lr = LHS.getLiveRangeContaining(VNI->def.getPrevSlot());
-      assert(lr && "Cannot find live range");
+      // The copy could be to an aliased physreg.
+      if (!lr) continue;
       RHSValsDefinedFromLHS[VNI] = lr->valno;
     }