Allow a register to be redefined multiple times in a basic block.

LiveVariableAnalysis was a bit picky about a register only being redefined once,
but that really isn't necessary.

Here is an example of chained INSERT_SUBREGs that we can handle now:

68      %reg1040<def> = INSERT_SUBREG %reg1040, %reg1028<kill>, 14
                register: %reg1040 +[70,134:0)
76      %reg1040<def> = INSERT_SUBREG %reg1040, %reg1029<kill>, 13
                register: %reg1040 replace range with [70,78:1) RESULT: %reg1040,0.000000e+00 = [70,78:1)[78,134:0)  0@78-(134) 1@70-(78)
84      %reg1040<def> = INSERT_SUBREG %reg1040, %reg1030<kill>, 12
                register: %reg1040 replace range with [78,86:2) RESULT: %reg1040,0.000000e+00 = [70,78:1)[78,86:2)[86,134:0)  0@86-(134) 1@70-(78) 2@78-(86)
92      %reg1040<def> = INSERT_SUBREG %reg1040, %reg1031<kill>, 11
                register: %reg1040 replace range with [86,94:3) RESULT: %reg1040,0.000000e+00 = [70,78:1)[78,86:2)[86,94:3)[94,134:0)  0@94-(134) 1@70-(78) 2@78-(86) 3@86-(94)

rdar://problem/8096390

llvm-svn: 106152

1 files changed, 2 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
index 349ea2c446c..22d62524f39 100644
--- a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -434,11 +434,6 @@ void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb,
       // are actually two values in the live interval.  Because of this we
       // need to take the LiveRegion that defines this register and split it
       // into two values.
-      // Two-address vregs should always only be redefined once.  This means
-      // that at this point, there should be exactly one value number in it.
-      assert((PartReDef || interval.containsOneValue()) &&
-             "Unexpected 2-addr liveint!");
-      SlotIndex DefIndex = interval.getValNumInfo(0)->def.getDefIndex();
       SlotIndex RedefIndex = MIIdx.getDefIndex();
       if (MO.isEarlyClobber())
         RedefIndex = MIIdx.getUseIndex();
@@ -446,8 +441,9 @@ void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb,
       const LiveRange *OldLR =
         interval.getLiveRangeContaining(RedefIndex.getUseIndex());
       VNInfo *OldValNo = OldLR->valno;
+      SlotIndex DefIndex = OldValNo->def.getDefIndex();
 
-      // Delete the initial value, which should be short and continuous,
+      // Delete the previous value, which should be short and continuous,
       // because the 2-addr copy must be in the same MBB as the redef.
       interval.removeRange(DefIndex, RedefIndex);