Factor out prelowerPhi for 32-bit targets. Disable adv phi lowering for ARM.

src/IcePhiLoweringImpl.h

Index: src/IcePhiLoweringImpl.h
diff --git a/src/IcePhiLoweringImpl.h b/src/IcePhiLoweringImpl.h
new file mode 100644
index 0000000000000000000000000000000000000000..cf932d61e214a043016c58f2e050dd7ca17a9234
--- /dev/null
+++ b/src/IcePhiLoweringImpl.h
@@ -0,0 +1,61 @@
+//===------ subzero/src/IcePhiLoweringImpl.h - Phi lowering -----*- C++ -*-===//
+//
+//                        The Subzero Code Generator
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This contains utilities for targets to lower Phis.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef SUBZERO_SRC_ICEPHILOWERINGIMPL_H
+#define SUBZERO_SRC_ICEPHILOWERINGIMPL_H
+
+#include "IceCfg.h"
+#include "IceCfgNode.h"
+#include "IceDefs.h"
+#include "IceInst.h"
+#include "IceOperand.h"
+
+namespace Ice {
+namespace PhiLowering {
+
+// Turn an i64 Phi instruction into a pair of i32 Phi instructions, to
+// preserve integrity of liveness analysis.  This is needed for 32-bit
+// targets.  This assumes the 32-bit target has loOperand, hiOperand,
+// and legalizeUndef methods.  Undef values are also legalized, since
+// loOperand() and hiOperand() don't expect Undef input.
+template <class TargetT>
+void prelowerPhis32Bit(TargetT *Target, CfgNode *Node, Cfg *Func) {
+  for (Inst &I : Node->getPhis()) {
+    auto Phi = llvm::dyn_cast<InstPhi>(&I);
+    if (Phi->isDeleted())
+      continue;
+    Variable *Dest = Phi->getDest();
+    if (Dest->getType() == IceType_i64) {
+      Variable *DestLo = llvm::cast<Variable>(Target->loOperand(Dest));
+      Variable *DestHi = llvm::cast<Variable>(Target->hiOperand(Dest));
+      InstPhi *PhiLo = InstPhi::create(Func, Phi->getSrcSize(), DestLo);
+      InstPhi *PhiHi = InstPhi::create(Func, Phi->getSrcSize(), DestHi);
+      for (SizeT I = 0; I < Phi->getSrcSize(); ++I) {
+        Operand *Src = Phi->getSrc(I);
+        CfgNode *Label = Phi->getLabel(I);
+        Src = Target->legalizeUndef(Src);
+        PhiLo->addArgument(Target->loOperand(Src), Label);
+        PhiHi->addArgument(Target->hiOperand(Src), Label);
+      }
+      Node->getPhis().push_back(PhiLo);
+      Node->getPhis().push_back(PhiHi);
+      Phi->setDeleted();
+    }
+  }
+}
+
+} // end of namespace PhiLowering
+} // end of namespace Ice
+
+#endif // SUBZERO_SRC_ICEPHILOWERINGIMPL_H