Fixing bug committed in rev. 278321

In theory the indices of RC (and thus the index used for LiveRegs) may differ from the indices of OpRC.
Fixed the code to extract the correct RC index.
OpRC contains the first X consecutive elements of RC, and thus their indices are currently de facto the same, therefore a test cannot be added at this point.

Differential Revision: https://reviews.llvm.org/D23491

llvm-svn: 278923

1 files changed, 6 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/ExecutionDepsFix.cpp b/llvm/lib/CodeGen/ExecutionDepsFix.cpp
index 5f91db9251c..213dd58a31d 100644
--- a/llvm/lib/CodeGen/ExecutionDepsFix.cpp
+++ b/llvm/lib/CodeGen/ExecutionDepsFix.cpp
@@ -509,12 +509,15 @@ void ExeDepsFix::pickBestRegisterForUndef(MachineInstr *MI, unsigned OpIdx,
   // max clearance or clearance higher than Pref.
   unsigned MaxClearance = 0;
   unsigned MaxClearanceReg = OriginalReg;
-  for (unsigned rx = 0; rx < OpRC->getNumRegs(); ++rx) {
-    unsigned Clearance = CurInstr - LiveRegs[rx].Def;
+  for (auto Reg : OpRC->getRegisters()) {
+    assert(AliasMap[Reg].size() == 1 &&
+           "Reg is expected to be mapped to a single index");
+    int RCrx = *regIndices(Reg).begin();
+    unsigned Clearance = CurInstr - LiveRegs[RCrx].Def;
     if (Clearance <= MaxClearance)
       continue;
     MaxClearance = Clearance;
-    MaxClearanceReg = OpRC->getRegister(rx);
+    MaxClearanceReg = Reg;
 
     if (MaxClearance > Pref)
       break;