Handle early-clobber registers in the aggressive anti-dep breaker

The aggressive anti-dep breaker, used by the PowerPC backend during post-RA
scheduling (but is available to all targets), did not handle early-clobber MI
operands (at all). When constructing the list of available registers for the
replacement of some def operand, check the using instructions, and remove
registers assigned to early-clobbered defs from the set.

Fixes PR21452.

llvm-svn: 223727

1 files changed, 15 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/AggressiveAntiDepBreaker.cpp b/llvm/lib/CodeGen/AggressiveAntiDepBreaker.cpp
index 91c1314d283..69c368524a7 100644
--- a/llvm/lib/CodeGen/AggressiveAntiDepBreaker.cpp
+++ b/llvm/lib/CodeGen/AggressiveAntiDepBreaker.cpp
@@ -673,6 +673,21 @@ bool AggressiveAntiDepBreaker::FindSuitableFreeRegisters(
           goto next_super_reg;
       }
 
+      // We cannot rename 'Reg' to 'NewReg' if one of the uses of 'Reg' also
+      // defines 'NewReg' via an early-clobber operand.
+      auto Range = RegRefs.equal_range(Reg);
+      for (auto Q = Range.first, QE = Range.second; Q != QE; ++Q) {
+        auto UseMI = Q->second.Operand->getParent();
+        int Idx = UseMI->findRegisterDefOperandIdx(NewReg, false, true, TRI);
+        if (Idx == -1)
+          continue;
+
+        if (UseMI->getOperand(Idx).isEarlyClobber()) {
+          DEBUG(dbgs() << "(ec)");
+          goto next_super_reg;
+        }
+      }
+
       // Record that 'Reg' can be renamed to 'NewReg'.
       RenameMap.insert(std::pair<unsigned, unsigned>(Reg, NewReg));
     }