Handle ARM "ret void" and function alignment with proper padding.

src/IceInstARM32.cpp

+//===- subzero/src/IceInstARM32.cpp - ARM32 instruction implementation ----===//
+//
+//                        The Subzero Code Generator
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the InstARM32 and OperandARM32 classes,
+// primarily the constructors and the dump()/emit() methods.
+//
+//===----------------------------------------------------------------------===//
+
+#include "assembler_arm32.h"
+#include "IceCfg.h"
+#include "IceCfgNode.h"
+#include "IceInst.h"
+#include "IceInstARM32.h"
+#include "IceOperand.h"
+#include "IceRegistersARM32.h"
+#include "IceTargetLoweringARM32.h"
+
+namespace Ice {
+
+namespace {
+
+const struct TypeARM32Attributes_ {
+  const char *WidthString; // b, h, <blank>, or d
+  int8_t SExtAddrOffsetBits;
+  int8_t ZExtAddrOffsetBits;
+} TypeARM32Attributes[] = {
+#define X(tag, elementty, width, sbits, ubits)                                 \
+  { width, sbits, ubits }                                                      \
+  ,
+    ICETYPEARM32_TABLE
+#undef X
+};
+
+} // end of anonymous namespace
+
+const char *InstARM32::getWidthString(Type Ty) {
+  return TypeARM32Attributes[Ty].WidthString;
+}
+
+bool OperandARM32Mem::canHoldOffset(Type Ty, bool SignExt, int32_t Offset) {
+  int32_t Bits = SignExt ? TypeARM32Attributes[Ty].SExtAddrOffsetBits
+                         : TypeARM32Attributes[Ty].ZExtAddrOffsetBits;
+  if (Bits == 0)
+    return Offset == 0;
+  // Note that encodings for offsets are sign-magnitude for ARM, so we check
+  // with IsAbsoluteUint().
+  if (isScalarFloatingType(Ty))
+    return Utils::IsAligned(Offset, 4) && Utils::IsAbsoluteUint(Bits, Offset);
+  return Utils::IsAbsoluteUint(Bits, Offset);
+}
+
+InstARM32Ret::InstARM32Ret(Cfg *Func, Variable *LR, Variable *Source)
+    : InstARM32(Func, InstARM32::Ret, Source ? 2 : 1, nullptr) {
+  addSource(LR);
+  if (Source)
+    addSource(Source);
+}
+
+// ======================== Dump routines ======================== //
+
+void InstARM32::dump(const Cfg *Func) const {
+  if (!ALLOW_DUMP)
+    return;
+  Ostream &Str = Func->getContext()->getStrDump();
+  Str << "[ARM32] ";
+  Inst::dump(Func);
+}
+
+void InstARM32Ret::emit(const Cfg *Func) const {
+  if (!ALLOW_DUMP)
+    return;
+  assert(getSrcSize() > 0);
+  Variable *LR = llvm::cast<Variable>(getSrc(0));
+  assert(LR->hasReg());
+  assert(LR->getRegNum() == RegARM32::Reg_lr);
+  Ostream &Str = Func->getContext()->getStrEmit();
+  Str << "\tbx\t";
+  LR->emit(Func);
+}
+
+void InstARM32Ret::emitIAS(const Cfg *Func) const {
+  (void)Func;
+  llvm_unreachable("Not yet implemented");
+}
+
+void InstARM32Ret::dump(const Cfg *Func) const {
+  if (!ALLOW_DUMP)
+    return;
+  Ostream &Str = Func->getContext()->getStrDump();
+  Type Ty = (getSrcSize() == 1 ? IceType_void : getSrc(0)->getType());
+  Str << "ret." << Ty << " ";
+  dumpSources(Func);
+}
+
+} // end of namespace Ice