[AMDGPU] Add AMDGPU specific variadic operation MCExprs

llvm/docs/AMDGPUUsage.rst

@@ -1534,6 +1534,25 @@ The AMDGPU backend supports the following calling conventions:
 
      =============================== ==========================================================
 
+AMDGPU MCExpr
+-------------
+
+As part of the AMDGPU MC layer, AMDGPU provides the following target specific
+``MCExpr``\s.
+
+  .. table:: AMDGPU MCExpr types:
+     :name: amdgpu-mcexpr-table
+
+     =================== ================= ========================================================
+     MCExpr              Operands          Return value
+     =================== ================= ========================================================
+     ``max(arg, ...)``   1 or more         Variadic signed operation that returns the maximum
+                                           value of all its arguments.
+
+     ``or(arg, ...)``    1 or more         Variadic signed operation that returns the bitwise-or
+                                           result of all its arguments.
+
+     =================== ================= ========================================================
 
 .. _amdgpu-elf-code-object:
 

llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "AMDKernelCodeT.h"
+#include "MCTargetDesc/AMDGPUMCExpr.h"
 #include "MCTargetDesc/AMDGPUMCTargetDesc.h"
 #include "MCTargetDesc/AMDGPUTargetStreamer.h"
 #include "SIDefines.h"
@@ -1816,6 +1817,7 @@ class AMDGPUAsmParser : public MCTargetAsmParser {
 
 public:
   void onBeginOfFile() override;
+  bool parsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) override;
 
   ParseStatus parseCustomOperand(OperandVector &Operands, unsigned MCK);
 
@@ -8277,6 +8279,59 @@ void AMDGPUAsmParser::onBeginOfFile() {
     getTargetStreamer().EmitDirectiveAMDGCNTarget();
 }
 
+/// Parse AMDGPU specific expressions.
+///
+///  expr ::= or(expr, ...) |
+///           max(expr, ...)
+///
+bool AMDGPUAsmParser::parsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) {
+  using AGVK = AMDGPUVariadicMCExpr::VariadicKind;
+
+  if (isToken(AsmToken::Identifier)) {
+    StringRef TokenId = getTokenStr();
+    AGVK VK = StringSwitch<AGVK>(TokenId)
+                  .Case("max", AGVK::AGVK_Max)
+                  .Case("or", AGVK::AGVK_Or)
+                  .Default(AGVK::AGVK_None);
+
+    if (VK != AGVK::AGVK_None && peekToken().is(AsmToken::LParen)) {
+      SmallVector<const MCExpr *, 4> Exprs;
+      uint64_t CommaCount = 0;
+      lex(); // Eat 'max'/'or'
+      lex(); // Eat '('
+      while (true) {
+        if (trySkipToken(AsmToken::RParen)) {
+          if (Exprs.empty()) {
+            Error(getToken().getLoc(),
+                  "empty " + Twine(TokenId) + " expression");
+            return true;
+          }
+          if (CommaCount + 1 != Exprs.size()) {
+            Error(getToken().getLoc(),
+                  "mismatch of commas in " + Twine(TokenId) + " expression");
+            return true;
+          }
+          Res = AMDGPUVariadicMCExpr::create(VK, Exprs, getContext());
+          return false;
+        }
+        const MCExpr *Expr;
+        if (getParser().parseExpression(Expr, EndLoc))
+          return true;
+        Exprs.push_back(Expr);
+        bool LastTokenWasComma = trySkipToken(AsmToken::Comma);
+        if (LastTokenWasComma)
+          CommaCount++;
+        if (!LastTokenWasComma && !isToken(AsmToken::RParen)) {
+          Error(getToken().getLoc(),
+                "unexpected token in " + Twine(TokenId) + " expression");
+          return true;
+        }
+      }
+    }
+  }
+  return getParser().parsePrimaryExpr(Res, EndLoc, nullptr);
+}
+
 ParseStatus AMDGPUAsmParser::parseOModSI(OperandVector &Operands) {
   StringRef Name = getTokenStr();
   if (Name == "mul") {

llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.cpp

@@ -0,0 +1,94 @@
+//===- AMDGPUMCExpr.cpp - AMDGPU specific MC expression classes -----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPUMCExpr.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCValue.h"
+#include "llvm/Support/Allocator.h"
+#include "llvm/Support/raw_ostream.h"
+#include <optional>
+
+using namespace llvm;
+
+const AMDGPUVariadicMCExpr *
+AMDGPUVariadicMCExpr::create(VariadicKind Kind, ArrayRef<const MCExpr *> Args,
+                             MCContext &Ctx) {
+  return new (Ctx) AMDGPUVariadicMCExpr(Kind, Args);
+}
+
+const MCExpr *AMDGPUVariadicMCExpr::getSubExpr(size_t Index) const {
+  assert(Index < Args.size() &&
+         "Indexing out of bounds AMDGPUVariadicMCExpr sub-expr");
+  return Args[Index];
+}
+
+void AMDGPUVariadicMCExpr::printImpl(raw_ostream &OS,
+                                     const MCAsmInfo *MAI) const {
+  switch (Kind) {
+  default:
+    llvm_unreachable("Unknown AMDGPUVariadicMCExpr kind.");
+  case AGVK_Or:
+    OS << "or(";
+    break;
+  case AGVK_Max:
+    OS << "max(";
+    break;
+  }
+  for (auto It = Args.begin(); It != Args.end(); ++It) {
+    (*It)->print(OS, MAI, /*InParens=*/false);
+    if ((It + 1) != Args.end())
+      OS << ", ";
+  }
+  OS << ')';
+}
+
+static int64_t op(AMDGPUVariadicMCExpr::VariadicKind Kind, int64_t Arg1,
+                  int64_t Arg2) {
+  switch (Kind) {
+  default:
+    llvm_unreachable("Unknown AMDGPUVariadicMCExpr kind.");
+  case AMDGPUVariadicMCExpr::AGVK_Max:
+    return std::max(Arg1, Arg2);
+  case AMDGPUVariadicMCExpr::AGVK_Or:
+    return Arg1 | Arg2;
+  }
+}
+
+bool AMDGPUVariadicMCExpr::evaluateAsRelocatableImpl(
+    MCValue &Res, const MCAsmLayout *Layout, const MCFixup *Fixup) const {
+  std::optional<int64_t> Total;
+
+  for (const MCExpr *Arg : Args) {
+    MCValue ArgRes;
+    if (!Arg->evaluateAsRelocatable(ArgRes, Layout, Fixup) ||
+        !ArgRes.isAbsolute())
+      return false;
+
+    if (!Total.has_value())
+      Total = ArgRes.getConstant();
+    Total = op(Kind, *Total, ArgRes.getConstant());
+  }
+
+  Res = MCValue::get(*Total);
+  return true;
+}
+
+void AMDGPUVariadicMCExpr::visitUsedExpr(MCStreamer &Streamer) const {
+  for (const MCExpr *Arg : Args)
+    Streamer.visitUsedExpr(*Arg);
+}
+
+MCFragment *AMDGPUVariadicMCExpr::findAssociatedFragment() const {
+  for (const MCExpr *Arg : Args) {
+    if (Arg->findAssociatedFragment())
+      return Arg->findAssociatedFragment();
+  }
+  return nullptr;
+}

llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.h

@@ -0,0 +1,74 @@
+//===- AMDGPUMCExpr.h - AMDGPU specific MC expression classes ---*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_AMDGPU_MCTARGETDESC_AMDGPUMCEXPR_H
+#define LLVM_LIB_TARGET_AMDGPU_MCTARGETDESC_AMDGPUMCEXPR_H
+
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/MC/MCExpr.h"
+
+namespace llvm {
+
+/// AMDGPU target specific variadic MCExpr operations.
+///
+/// Takes in a minimum of 1 argument to be used with an operation. The supported
+/// operations are:
+///   - (bitwise) or
+///   - max
+///
+/// \note If the 'or'/'max' operations are provided only a single argument, the
+/// operation will act as a no-op and simply resolve as the provided argument.
+///
+class AMDGPUVariadicMCExpr : public MCTargetExpr {
+public:
+  enum VariadicKind { AGVK_None, AGVK_Or, AGVK_Max };
+
+private:
+  VariadicKind Kind;
+  SmallVector<const MCExpr *, 2> Args;
+
+  AMDGPUVariadicMCExpr(VariadicKind Kind, ArrayRef<const MCExpr *> Args)
+      : Kind(Kind), Args(Args) {
+    assert(Args.size() >= 1 && "Needs a minimum of one expression.");
+    assert(Kind != AGVK_None &&
+           "Cannot construct AMDGPUVariadicMCExpr of kind none.");
+  }
+
+public:
+  static const AMDGPUVariadicMCExpr *
+  create(VariadicKind Kind, ArrayRef<const MCExpr *> Args, MCContext &Ctx);
+
+  static const AMDGPUVariadicMCExpr *createOr(ArrayRef<const MCExpr *> Args,
+                                              MCContext &Ctx) {
+    return create(VariadicKind::AGVK_Or, Args, Ctx);
+  }
+
+  static const AMDGPUVariadicMCExpr *createMax(ArrayRef<const MCExpr *> Args,
+                                               MCContext &Ctx) {
+    return create(VariadicKind::AGVK_Max, Args, Ctx);
+  }
+
+  VariadicKind getKind() const { return Kind; }
+  const MCExpr *getSubExpr(size_t Index) const;
+
+  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;
+  void fixELFSymbolsInTLSFixups(MCAssembler &) const override{};
+
+  static bool classof(const MCExpr *E) {
+    return E->getKind() == MCExpr::Target;
+  }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_LIB_TARGET_AMDGPU_MCTARGETDESC_AMDGPUMCEXPR_H

llvm/lib/Target/AMDGPU/MCTargetDesc/CMakeLists.txt

@@ -5,6 +5,7 @@ add_llvm_component_library(LLVMAMDGPUDesc
   AMDGPUInstPrinter.cpp
   AMDGPUMCAsmInfo.cpp
   AMDGPUMCCodeEmitter.cpp
+  AMDGPUMCExpr.cpp
   AMDGPUMCTargetDesc.cpp
   AMDGPUTargetStreamer.cpp
   R600InstPrinter.cpp