diff --git a/Makefile.standalone b/Makefile.standalone
index 0d0bad2..47afc8b 100644
--- a/Makefile.standalone
+++ b/Makefile.standalone
@@ -328,10 +328,10 @@
 	  --toolchain-root $(TOOLCHAIN_ROOT) \
 	  -i x8632,native,sse2 -i x8632,native,sse4.1,test_vector_ops \
 	  -i x8632,sandbox,sse4.1,Om1 \
-	  -i arm32,native,neon,Om1,simple_loop \
-	  -i arm32,native,neon,Om1,mem_intrin \
-	  -i arm32,native,neon,Om1,test_stacksave \
-	  -i arm32,native,neon,Om1,test_strengthreduce
+	  -i arm32,native,neon,simple_loop \
+	  -i arm32,native,neon,mem_intrin \
+	  -i arm32,native,neon,test_stacksave \
+	  -i arm32,native,neon,test_strengthreduce
 	PNACL_BIN_PATH=$(PNACL_BIN_PATH) \
 	$(LLVM_SRC_PATH)/utils/lit/lit.py -sv crosstest/Output
 endif
diff --git a/src/IceClFlags.cpp b/src/IceClFlags.cpp
index f1aebd2..2d2e641 100644
--- a/src/IceClFlags.cpp
+++ b/src/IceClFlags.cpp
@@ -390,7 +390,15 @@
   OutFlags.setFunctionSections(::FunctionSections);
   OutFlags.setNumTranslationThreads(::NumThreads);
   OutFlags.setOptLevel(::OLevel);
-  OutFlags.setPhiEdgeSplit(::EnablePhiEdgeSplit);
+  if (::TargetArch == Target_ARM32) {
+    // TODO(jvoung): We need lowerPhiAssignments to handle spilling
+    // more than one register, since some ARM lowerAssign sequences
+    // may require more than one register. For now, disable PhiEdgeSplit
+    // to avoid requiring lowerPhiAssignments.
+    OutFlags.setPhiEdgeSplit(false);
+  } else {
+    OutFlags.setPhiEdgeSplit(::EnablePhiEdgeSplit);
+  }
   OutFlags.setRandomSeed(::RandomSeed);
   OutFlags.setShouldDoNopInsertion(::ShouldDoNopInsertion);
   OutFlags.setShouldRandomizeRegAlloc(::RandomizeRegisterAllocation);
diff --git a/src/IcePhiLoweringImpl.h b/src/IcePhiLoweringImpl.h
new file mode 100644
index 0000000..cf932d6
--- /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
diff --git a/src/IceTargetLoweringARM32.cpp b/src/IceTargetLoweringARM32.cpp
index 0dbcfb1..e09a85f 100644
--- a/src/IceTargetLoweringARM32.cpp
+++ b/src/IceTargetLoweringARM32.cpp
@@ -24,6 +24,7 @@
 #include "IceInstARM32.h"
 #include "IceLiveness.h"
 #include "IceOperand.h"
+#include "IcePhiLoweringImpl.h"
 #include "IceRegistersARM32.h"
 #include "IceTargetLoweringARM32.def"
 #include "IceUtils.h"
@@ -2410,12 +2411,8 @@
   _trap();
 }
 
-// Turn an i64 Phi instruction into a pair of i32 Phi instructions, to
-// preserve integrity of liveness analysis.  Undef values are also
-// turned into zeroes, since loOperand() and hiOperand() don't expect
-// Undef input.
 void TargetARM32::prelowerPhis() {
-  UnimplementedError(Func->getContext()->getFlags());
+  PhiLowering::prelowerPhis32Bit<TargetARM32>(this, Context.getNode(), Func);
 }
 
 // Lower the pre-ordered list of assignments into mov instructions.
diff --git a/src/IceTargetLoweringARM32.h b/src/IceTargetLoweringARM32.h
index 4c95d3c..87faf01 100644
--- a/src/IceTargetLoweringARM32.h
+++ b/src/IceTargetLoweringARM32.h
@@ -103,6 +103,7 @@
   bool hasCPUFeature(TargetARM32Features::ARM32InstructionSet I) const {
     return CPUFeatures.hasFeature(I);
   }
+  Operand *legalizeUndef(Operand *From, int32_t RegNum = Variable::NoRegister);
 
 protected:
   explicit TargetARM32(Cfg *Func);
@@ -146,7 +147,6 @@
   Operand *legalize(Operand *From, LegalMask Allowed = Legal_All,
                     int32_t RegNum = Variable::NoRegister);
   Variable *legalizeToVar(Operand *From, int32_t RegNum = Variable::NoRegister);
-  Operand *legalizeUndef(Operand *From, int32_t RegNum = Variable::NoRegister);
   OperandARM32Mem *formMemoryOperand(Operand *Ptr, Type Ty);
 
   Variable *makeReg(Type Ty, int32_t RegNum = Variable::NoRegister);
diff --git a/src/IceTargetLoweringX86Base.h b/src/IceTargetLoweringX86Base.h
index 69b88ee..7963b01 100644
--- a/src/IceTargetLoweringX86Base.h
+++ b/src/IceTargetLoweringX86Base.h
@@ -159,6 +159,7 @@
   typename Traits::InstructionSet getInstructionSet() const final {
     return InstructionSet;
   }
+  Operand *legalizeUndef(Operand *From, int32_t RegNum = Variable::NoRegister);
 
 protected:
   explicit TargetX86Base(Cfg *Func);
@@ -230,7 +231,6 @@
   Operand *legalize(Operand *From, LegalMask Allowed = Legal_All,
                     int32_t RegNum = Variable::NoRegister);
   Variable *legalizeToVar(Operand *From, int32_t RegNum = Variable::NoRegister);
-  Operand *legalizeUndef(Operand *From, int32_t RegNum = Variable::NoRegister);
   /// Legalize the first source operand for use in the cmp instruction.
   Operand *legalizeSrc0ForCmp(Operand *Src0, Operand *Src1);
   /// Turn a pointer operand into a memory operand that can be
diff --git a/src/IceTargetLoweringX86BaseImpl.h b/src/IceTargetLoweringX86BaseImpl.h
index 0ac63b8..cf786f4 100644
--- a/src/IceTargetLoweringX86BaseImpl.h
+++ b/src/IceTargetLoweringX86BaseImpl.h
@@ -25,6 +25,7 @@
 #include "IceGlobalInits.h"
 #include "IceLiveness.h"
 #include "IceOperand.h"
+#include "IcePhiLoweringImpl.h"
 #include "IceUtils.h"
 #include "llvm/Support/MathExtras.h"
 
@@ -4696,30 +4697,8 @@
   // Pause constant blinding or pooling, blinding or pooling will be done later
   // during phi lowering assignments
   BoolFlagSaver B(RandomizationPoolingPaused, true);
-
-  CfgNode *Node = Context.getNode();
-  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>(loOperand(Dest));
-      Variable *DestHi = llvm::cast<Variable>(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 = legalizeUndef(Src);
-        PhiLo->addArgument(loOperand(Src), Label);
-        PhiHi->addArgument(hiOperand(Src), Label);
-      }
-      Node->getPhis().push_back(PhiLo);
-      Node->getPhis().push_back(PhiHi);
-      Phi->setDeleted();
-    }
-  }
+  PhiLowering::prelowerPhis32Bit<TargetX86Base<Machine>>(
+      this, Context.getNode(), Func);
 }
 
 bool isMemoryOperand(const Operand *Opnd) {
diff --git a/tests_lit/llvm2ice_tests/64bit.pnacl.ll b/tests_lit/llvm2ice_tests/64bit.pnacl.ll
index b88babe..cc32a87 100644
--- a/tests_lit/llvm2ice_tests/64bit.pnacl.ll
+++ b/tests_lit/llvm2ice_tests/64bit.pnacl.ll
@@ -158,6 +158,28 @@
 ; ARM32:      bl      {{.*}} ignore64BitArgNoInline
 ; ARM32:      add     sp, {{.*}} #16
 
+define internal i32 @pass64BitUndefArg() {
+entry:
+  %call = call i32 @ignore64BitArgNoInline(i64 0, i32 123, i64 undef)
+  ret i32 %call
+}
+; CHECK-LABEL: pass64BitUndefArg
+; CHECK: sub esp
+; CHECK: mov DWORD PTR{{.*}},0x7b
+; CHECK: mov DWORD PTR{{.*}},0x0
+; CHECK: call {{.*}} R_{{.*}} ignore64BitArgNoInline
+; OPTM1-LABEL: pass64BitUndefArg
+; OPTM1: sub esp
+; OPTM1: mov DWORD PTR{{.*}},0x7b
+; OPTM1: mov DWORD PTR{{.*}},0x0
+; OPTM1: call {{.*}} R_{{.*}} ignore64BitArgNoInline
+; ARM32-LABEL: pass64BitUndefArg
+; ARM32: sub sp
+; ARM32: movw {{.*}}, #0
+; ARM32: str
+; ARM32: movw {{.*}}, #123
+; ARM32: bl {{.*}} ignore64BitArgNoInline
+
 define internal i64 @return64BitArg(i64 %padding, i64 %a) {
 entry:
   ret i64 %a
@@ -1744,3 +1766,49 @@
 ; OPTM1-NOT: cmp 0x{{[0-9a-f]+}},
 ; ARM32-LABEL: icmpLt64Imm
 ; ARM32-NOT: cmp #{{[0-9a-f]+}},
+
+define internal i64 @phi64Imm(i32 %x, i64 %y, i64 %z) {
+entry:
+  %cond = icmp eq i32 %x, 88
+  br i1 %cond, label %branch1, label %branch2
+branch1:
+  %tmp = add i64 %y, %z
+  br label %branch2
+
+branch2:
+  %merge = phi i64 [ %tmp, %branch1 ], [ 20014547621496, %entry ]
+  ret i64 %merge
+}
+; CHECK-LABEL: phi64Imm
+; CHECK: mov {{.*}},0x5678
+; CHECK: mov {{.*}},0x1234
+; OPTM1-LABEL: phi64Imm
+; OPTM1: mov {{.*}},0x5678
+; OPTM1: mov {{.*}},0x1234
+; ARM32-LABEL: phi64Imm
+; ARM32: movw {{.*}}, #22136 ; 0x5678
+; ARM32: movw {{.*}}, #4660  ; 0x1234
+
+define internal i64 @phi64Undef(i32 %x, i64 %y, i64 %z) {
+entry:
+  %cond = icmp eq i32 %x, 88
+  br i1 %cond, label %branch1, label %branch2
+branch1:
+  %tmp = add i64 %y, %z
+  br label %branch2
+
+branch2:
+  %merge = phi i64 [ %tmp, %branch1 ], [ undef, %entry ]
+  ret i64 %merge
+}
+
+; CHECK-LABEL: phi64Undef
+; CHECK: mov {{.*}},0x0
+; CHECK: mov {{.*}},0x0
+; OPTM1-LABEL: phi64Undef
+; OPTM1: mov {{.*}},0x0
+; OPTM1: mov {{.*}},0x0
+; ARM32-LABEL: phi64Undef
+; ARM32: mov {{.*}} #0
+; ARM32: mov {{.*}} #0
+