[AVR] Add AVRMCExpr

[dylanmckay]

Summary

This adds the AVRMCExpr headers and implementation.

[arsenm]

lib/Target/AVR/MCTargetDesc/AVRMCExpr.cpp

24

const char* const?

45–50

Single quote around single chars

65–66

No return after else

169

const char?

177

nullptr

181–183

There's an llvm::find_if which takes a range instead of the separate iterators

[dylanmckay]

Mat's code review

[dylanmckay]

lib/Target/AVR/MCTargetDesc/AVRMCExpr.cpp

181–183

I can't seem to get it working, it tries to call .begin() on the array, which doesn't exist.

[dylanmckay]

Ping

[dylanmckay]

Ping

[kparzysz]

lib/Target/AVR/MCTargetDesc/AVRMCExpr.cpp

100

This should happen before you convert it to an unsigned value.

131

"AVR::Fixups Kind = AVR::Fixups::LastTargetFixupKind" would be better to indicate an invalid value.

Also, variable names generally start with an upper case.

[kparzysz]

Also, is it possible to have some basic testcase for this?

[dylanmckay]

Evaulate negatives using signed integers in AVRMCExpr::evaulateAsInt64

Use AVR::Fixups::LastTargetFixupKind to mark an invalid value

[dylanmckay]

I'm not able to add tests for this just yet, there are still several major parts of the backend missing, so we can't even run llc just yet.

I have unit tests for every single variant of AVRMCExpr, but I can't upstream them until we can actually assemble it.

lib/Target/AVR/MCTargetDesc/AVRFixupKinds.h

+//===-- AVRFixupKinds.h - AVR Specific Fixup Entries ------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_AVR_FIXUP_KINDS_H
+#define LLVM_AVR_FIXUP_KINDS_H
+
+#include "llvm/MC/MCFixup.h"
+
+namespace llvm {
+namespace AVR {
+
+/// The set of supported fixups.
+///
+/// Although most of the current fixup types reflect a unique relocation
+/// one can have multiple fixup types for a given relocation and thus need
+/// to be uniquely named.
+///
+/// \note This table *must* be in the same order of
+///       MCFixupKindInfo Infos[AVR::NumTargetFixupKinds]
+///       in `AVRAsmBackend.cpp`.
+enum Fixups {
+  /// A 32-bit AVR fixup.
+  fixup_32 = FirstTargetFixupKind,
+
+  /// A 7-bit PC-relative fixup for the family of conditional
+  /// branches which take 7-bit targets (BRNE,BRGT,etc).
+  fixup_7_pcrel,
+  /// A 12-bit PC-relative fixup for the family of branches
+  /// which take 12-bit targets (RJMP,RCALL,etc).
+  /// \note Although the fixup is labelled as 13 bits, it
+  ///       is actually only encoded in 12. The reason for
+  ///       The nonmenclature is that AVR branch targets are
+  ///       rightshifted by 1, because instructions are always
+  ///       aligned to 2 bytes, so the 0'th bit is always 0.
+  ///       This way there is 13-bits of precision.
+  fixup_13_pcrel,
+
+  /// A 16-bit address.
+  fixup_16,
+  /// A 16-bit program memory address.
+  fixup_16_pm,
+
+  /// Replaces the 8-bit immediate with another value.
+  fixup_ldi,
+
+  /// Replaces the immediate operand of a 16-bit `Rd, K` instruction
+  /// with the lower 8 bits of a 16-bit value (bits 0-7).
+  fixup_lo8_ldi,
+  /// Replaces the immediate operand of a 16-bit `Rd, K` instruction
+  /// with the upper 8 bits of a 16-bit value (bits 8-15).
+  fixup_hi8_ldi,
+  /// Replaces the immediate operand of a 16-bit `Rd, K` instruction
+  /// with the upper 8 bits of a 24-bit value (bits 16-23).
+  fixup_hh8_ldi,
+  /// Replaces the immediate operand of a 16-bit `Rd, K` instruction
+  /// with the upper 8 bits of a 32-bit value (bits 24-31).
+  fixup_ms8_ldi,
+
+  /// Replaces the immediate operand of a 16-bit `Rd, K` instruction
+  /// with the lower 8 bits of a negated 16-bit value (bits 0-7).
+  fixup_lo8_ldi_neg,
+  /// Replaces the immediate operand of a 16-bit `Rd, K` instruction
+  /// with the upper 8 bits of a negated 16-bit value (bits 8-15).
+  fixup_hi8_ldi_neg,
+  /// Replaces the immediate operand of a 16-bit `Rd, K` instruction
+  /// with the upper 8 bits of a negated negated 24-bit value (bits 16-23).
+  fixup_hh8_ldi_neg,
+  /// Replaces the immediate operand of a 16-bit `Rd, K` instruction
+  /// with the upper 8 bits of a negated negated 32-bit value (bits 24-31).
+  fixup_ms8_ldi_neg,
+
+  /// Replaces the immediate operand of a 16-bit `Rd, K` instruction
+  /// with the lower 8 bits of a 16-bit program memory address value (bits 0-7).
+  fixup_lo8_ldi_pm,
+  /// Replaces the immediate operand of a 16-bit `Rd, K` instruction
+  /// with the upper 8 bits of a 16-bit program memory address value (bits
+  /// 8-15).
+  fixup_hi8_ldi_pm,
+  /// Replaces the immediate operand of a 16-bit `Rd, K` instruction
+  /// with the upper 8 bits of a 24-bit program memory address value (bits
+  /// 16-23).
+  fixup_hh8_ldi_pm,
+
+  /// Replaces the immediate operand of a 16-bit `Rd, K` instruction
+  /// with the lower 8 bits of a negated 16-bit program memory address value
+  /// (bits 0-7).
+  fixup_lo8_ldi_pm_neg,
+  /// Replaces the immediate operand of a 16-bit `Rd, K` instruction
+  /// with the upper 8 bits of a negated 16-bit program memory address value
+  /// (bits 8-15).
+  fixup_hi8_ldi_pm_neg,
+  /// Replaces the immediate operand of a 16-bit `Rd, K` instruction
+  /// with the upper 8 bits of a negated 24-bit program memory address value
+  /// (bits 16-23).
+  fixup_hh8_ldi_pm_neg,
+
+  /// A 22-bit fixup for the target of a `CALL k` or `JMP k` instruction.
+  fixup_call,
+
+  fixup_6,
+  /// A symbol+addr fixup for the `LDD <x>+<n>, <r>" family of instructions.
+  fixup_6_adiw,
+
+  fixup_lo8_ldi_gs,
+  fixup_hi8_ldi_gs,
+
+  fixup_8,
+  fixup_8_lo8,
+  fixup_8_hi8,
+  fixup_8_hlo8,
+
+  /// Fixup to calculate the difference between two symbols.
+  /// Is the only stateful fixup. We do not support it yet.
+  fixup_sym_diff,
+  fixup_16_ldst,
+
+  fixup_lds_sts_16,
+
+  /// A 6-bit port address.
+  fixup_port6,
+  /// A 5-bit port address.
+  fixup_port5,
+
+  // Marker
+  LastTargetFixupKind,
+  NumTargetFixupKinds = LastTargetFixupKind - FirstTargetFixupKind
+};
+
+namespace fixups {
+
+/// Adjusts the value of a branch target.
+/// All branch targets in AVR are rightshifted by 1 to take advantage
+/// of the fact that all instructions are aligned to addresses of size
+/// 2, so bit 0 of an address is always 0. This gives us another bit
+/// of precision.
+/// \param[in,out] The target to adjust.
+template <typename T> inline void adjustBranchTarget(T &val) { val >>= 1; }
+
+} // end of namespace fixups
+}
+} // end of namespace llvm::AVR
+
+#endif // LLVM_AVR_FIXUP_KINDS_H

lib/Target/AVR/MCTargetDesc/AVRMCExpr.h

+//===-- AVRMCExpr.h - AVR specific MC expression classes --------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_AVR_MCEXPR_H
+#define LLVM_AVR_MCEXPR_H
+
+#include "llvm/MC/MCExpr.h"
+
+#include "MCTargetDesc/AVRFixupKinds.h"
+
+namespace llvm {
+
+/// A expression in AVR machine code.
+class AVRMCExpr : public MCTargetExpr {
+public:
+  /// Specifies the type of an expression.
+  enum VariantKind {
+    VK_AVR_None,
+
+    VK_AVR_HI8,  ///< Corresponds to `hi8()`.
+    VK_AVR_LO8,  ///< Corresponds to `lo8()`.
+    VK_AVR_HH8,  ///< Corresponds to `hlo8() and hh8()`.
+    VK_AVR_HHI8, ///< Corresponds to `hhi8()`.
+
+    VK_AVR_PM_LO8, ///< Corresponds to `pm_lo8()`.
+    VK_AVR_PM_HI8, ///< Corresponds to `pm_hi8()`.
+    VK_AVR_PM_HH8  ///< Corresponds to `pm_hh8()`.
+  };
+
+public:
+  /// Creates an AVR machine code expression.
+  static const AVRMCExpr *create(VariantKind Kind, const MCExpr *Expr,
+                                 bool isNegated, MCContext &Ctx);
+
+  /// Gets the type of the expression.
+  VariantKind getKind() const { return Kind; }
+  /// Gets the name of the expression.
+  const char *getName() const;
+  const MCExpr *getSubExpr() const { return SubExpr; }
+  /// Gets the fixup which corresponds to the expression.
+  AVR::Fixups getFixupKind() const;
+  /// Evaluates the fixup as a constant value.
+  bool evaluateAsConstant(int64_t &Result) const;
+
+  bool isNegated() const { return Negated; }
+  void setNegated(bool negated = true) { Negated = negated; }
+
+  void printImpl(raw_ostream &OS, const MCAsmInfo *MAI) const override;
+  bool evaluateAsRelocatableImpl(MCValue &Res, const MCAsmLayout *Layout,
+                                 const MCFixup *Fixup) const override;
+
+  void visitUsedExpr(MCStreamer &streamer) const override;
+
+  MCFragment *findAssociatedFragment() const override {
+    return getSubExpr()->findAssociatedFragment();
+  }
+
+  void fixELFSymbolsInTLSFixups(MCAssembler &Asm) const override {}
+
+  static bool classof(const MCExpr *E) {
+    return E->getKind() == MCExpr::Target;
+  }
+
+public:
+  static VariantKind getKindByName(StringRef Name);
+
+private:
+  int64_t evaluateAsInt64(int64_t Value) const;
+
+  const VariantKind Kind;
+  const MCExpr *SubExpr;
+  bool Negated;
+
+private:
+  explicit AVRMCExpr(VariantKind Kind, const MCExpr *Expr, bool Negated)
+      : Kind(Kind), SubExpr(Expr), Negated(Negated) {}
+  ~AVRMCExpr() {}
+};
+
+} // end namespace llvm
+
+#endif // LLVM_AVR_MCEXPR_H

lib/Target/AVR/MCTargetDesc/AVRMCExpr.cpp

+//===-- AVRMCExpr.cpp - AVR specific MC expression classes ----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AVRMCExpr.h"
+
+#include "llvm/MC/MCAssembler.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCValue.h"
+#include "llvm/MC/MCAsmLayout.h"
+
+namespace llvm {
+
+namespace {
+
+const struct ModifierEntry {
+  const char * const Spelling;
+  AVRMCExpr::VariantKind VariantKind;
+} ModifierNames[] = {
+    {"lo8", AVRMCExpr::VK_AVR_LO8},       {"hi8", AVRMCExpr::VK_AVR_HI8},
+    {"hh8", AVRMCExpr::VK_AVR_HH8}, // synonym with hlo8
+    {"hlo8", AVRMCExpr::VK_AVR_HH8},      {"hhi8", AVRMCExpr::VK_AVR_HHI8},
+
+    {"pm_lo8", AVRMCExpr::VK_AVR_PM_LO8}, {"pm_hi8", AVRMCExpr::VK_AVR_PM_HI8},
+    {"pm_hh8", AVRMCExpr::VK_AVR_PM_HH8},
+};
+
+} // end of anonymous namespace
+
+const AVRMCExpr *AVRMCExpr::create(VariantKind Kind, const MCExpr *Expr,
+                                   bool Negated, MCContext &Ctx) {
+  return new (Ctx) AVRMCExpr(Kind, Expr, Negated);
+}
+
+void AVRMCExpr::printImpl(raw_ostream &OS, const MCAsmInfo *MAI) const {
+  assert(Kind != VK_AVR_None);
+
+  if (isNegated())
+    OS << '-';
+
+  OS << getName() << '(';
+  getSubExpr()->print(OS, MAI);
+  OS << ')';
+}
+
+bool AVRMCExpr::evaluateAsConstant(int64_t &Result) const {
+  MCValue Value;
+
+  bool isRelocatable =
+      getSubExpr()->evaluateAsRelocatable(Value, nullptr, nullptr);
+
+  if (!isRelocatable)
+    return false;
+
+  if (Value.isAbsolute()) {
+    Result = evaluateAsInt64(Value.getConstant());
+    return true;
+  }
+
+  return false;
+}
+
+bool AVRMCExpr::evaluateAsRelocatableImpl(MCValue &Result,
+                                          const MCAsmLayout *Layout,
+                                          const MCFixup *Fixup) const {
+  MCValue Value;
+  bool isRelocatable = SubExpr->evaluateAsRelocatable(Value, Layout, Fixup);
+
+  if (!isRelocatable)
+    return false;
+
+  if (Value.isAbsolute()) {
+    Result = MCValue::get(evaluateAsInt64(Value.getConstant()));
+  } else {
+    if (!Layout) return false;
+
+    MCContext &Context = Layout->getAssembler().getContext();
+    const MCSymbolRefExpr *Sym = Value.getSymA();
+    MCSymbolRefExpr::VariantKind Modifier = Sym->getKind();
+    if (Modifier != MCSymbolRefExpr::VK_None)
+      return false;
+
+    Sym = MCSymbolRefExpr::create(&Sym->getSymbol(), Modifier, Context);
+    Result = MCValue::get(Sym, Value.getSymB(), Value.getConstant());
+  }
+
+  return true;
+}
+
+int64_t AVRMCExpr::evaluateAsInt64(int64_t Value) const {
+  uint64_t v = static_cast<uint64_t>(Value);
+
+  if (Negated)
+    v *= -1;
+
+  switch (Kind) {
+  case AVRMCExpr::VK_AVR_LO8:
+    break;
+  case AVRMCExpr::VK_AVR_HI8:
+    v >>= 8;
+    break;
+  case AVRMCExpr::VK_AVR_HH8:
+    v >>= 16;
+    break;
+  case AVRMCExpr::VK_AVR_HHI8:
+    v >>= 24;
+    break;
+  case AVRMCExpr::VK_AVR_PM_LO8:
+    v >>= 1;
+    break;
+  case AVRMCExpr::VK_AVR_PM_HI8:
+    v >>= 9;
+    break;
+  case AVRMCExpr::VK_AVR_PM_HH8:
+    v >>= 17;
+    break;
+
+  case AVRMCExpr::VK_AVR_None:
+    llvm_unreachable("Uninitialized expression.");
+  }
+  return v & 0xff;
+}
+
+AVR::Fixups AVRMCExpr::getFixupKind() const {
+  auto kind = AVR::Fixups(-1);
+
+  switch (getKind()) {
+  case VK_AVR_LO8:
+    kind = isNegated() ? AVR::fixup_lo8_ldi_neg : AVR::fixup_lo8_ldi;
+    break;
+  case VK_AVR_HI8:
+    kind = isNegated() ? AVR::fixup_hi8_ldi_neg : AVR::fixup_hi8_ldi;
+    break;
+  case VK_AVR_HH8:
+    kind = isNegated() ? AVR::fixup_hh8_ldi_neg : AVR::fixup_hh8_ldi;
+    break;
+  case VK_AVR_HHI8:
+    kind = isNegated() ? AVR::fixup_ms8_ldi_neg : AVR::fixup_ms8_ldi;
+    break;
+
+  case VK_AVR_PM_LO8:
+    kind = isNegated() ? AVR::fixup_lo8_ldi_pm_neg : AVR::fixup_lo8_ldi_pm;
+    break;
+  case VK_AVR_PM_HI8:
+    kind = isNegated() ? AVR::fixup_hi8_ldi_pm_neg : AVR::fixup_hi8_ldi_pm;
+    break;
+  case VK_AVR_PM_HH8:
+    kind = isNegated() ? AVR::fixup_hh8_ldi_pm_neg : AVR::fixup_hh8_ldi_pm;
+    break;
+
+  case VK_AVR_None:
+    llvm_unreachable("Uninitialized expression");
+  }
+
+  return kind;
+}
+
+void AVRMCExpr::visitUsedExpr(MCStreamer &Streamer) const {
+  Streamer.visitUsedExpr(*getSubExpr());
+}
+
+const char *AVRMCExpr::getName() const {
+  const auto &Modifier = std::find_if(
+      std::begin(ModifierNames), std::end(ModifierNames),
+      [this](ModifierEntry const &Mod) { return Mod.VariantKind == Kind; });
+
+  if (Modifier != std::end(ModifierNames)) {
+    return Modifier->Spelling;
+  }
+  return nullptr;
+}
+
+AVRMCExpr::VariantKind AVRMCExpr::getKindByName(StringRef Name) {
+  const auto &Modifier = std::find_if(
+      std::begin(ModifierNames), std::end(ModifierNames),
+      [&Name](ModifierEntry const &Mod) { return Mod.Spelling == Name; });
+
+  if (Modifier != std::end(ModifierNames)) {
+    return Modifier->VariantKind;
+  }
+  return VK_AVR_None;
+}
+
+} // end of namespace llvm
+

lib/Target/AVR/MCTargetDesc/CMakeLists.txt

 add_llvm_library(LLVMAVRDesc
   AVRELFStreamer.cpp
+  AVRMCExpr.cpp
   AVRTargetStreamer.cpp
 )
 
 add_dependencies(LLVMAVRDesc AVRCommonTableGen)