[llvm] [AMDGPU] Add AMDGPU specific variadic operation MCExprs (PR #82022)

Janek van Oirschot via llvm-commits llvm-commits at lists.llvm.org
Mon Feb 19 06:31:44 PST 2024


https://github.com/JanekvO updated https://github.com/llvm/llvm-project/pull/82022

>From a47ee7ba1bac1bd0c8a4384d5f3bef7011286fea Mon Sep 17 00:00:00 2001
From: Janek van Oirschot <janek.vanoirschot at amd.com>
Date: Fri, 16 Feb 2024 17:01:44 +0000
Subject: [PATCH 1/2] AMDGPU Variadic MCExprs

---
 .../AMDGPU/AsmParser/AMDGPUAsmParser.cpp      | 49 ++++++++++
 .../AMDGPU/MCTargetDesc/AMDGPUMCExpr.cpp      | 92 +++++++++++++++++++
 .../Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.h | 64 +++++++++++++
 .../Target/AMDGPU/MCTargetDesc/CMakeLists.txt |  1 +
 llvm/test/MC/AMDGPU/mcexpr_amd.s              | 92 +++++++++++++++++++
 llvm/test/MC/AMDGPU/mcexpr_amd_err.s          | 26 ++++++
 6 files changed, 324 insertions(+)
 create mode 100644 llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.cpp
 create mode 100644 llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.h
 create mode 100644 llvm/test/MC/AMDGPU/mcexpr_amd.s
 create mode 100644 llvm/test/MC/AMDGPU/mcexpr_amd_err.s

diff --git a/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp b/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
index 79ad6ddf7861fc..c878d9d26988e9 100644
--- a/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
+++ b/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"
@@ -1745,6 +1746,7 @@ class AMDGPUAsmParser : public MCTargetAsmParser {
 
 public:
   void onBeginOfFile() override;
+  bool parsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) override;
 
   ParseStatus parseCustomOperand(OperandVector &Operands, unsigned MCK);
 
@@ -8130,6 +8132,53 @@ 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::AMDGPUVariadicKind;
+
+  auto parseVariadicExpr = [&](AGVK Kind, const MCExpr *&res, SMLoc &EndLoc) {
+    std::vector<const MCExpr *> Exprs;
+    while (true) {
+      if (isToken(AsmToken::RParen)) {
+        if (Exprs.empty()) {
+          Error(getToken().getLoc(), "empty max/or expression");
+          return true;
+        }
+        lex();
+        res = AMDGPUVariadicMCExpr::create(Kind, Exprs, getContext());
+        return false;
+      }
+      const MCExpr *Expr;
+      if (getParser().parseExpression(Expr, EndLoc))
+        return true;
+      Exprs.push_back(Expr);
+      if (!trySkipToken(AsmToken::Comma) && !isToken(AsmToken::RParen)) {
+        Error(getToken().getLoc(), "unexpected token in max/or expression");
+        return true;
+      }
+    }
+  };
+
+  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)) {
+      lex(); // Eat 'max'/'or'
+      lex(); // Eat '('
+      return parseVariadicExpr(VK, Res, EndLoc);
+    }
+  }
+  return getParser().parsePrimaryExpr(Res, EndLoc, nullptr);
+}
+
 ParseStatus AMDGPUAsmParser::parseOModSI(OperandVector &Operands) {
   StringRef Name = getTokenStr();
   if (Name == "mul") {
diff --git a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.cpp b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.cpp
new file mode 100644
index 00000000000000..3b00de3756d924
--- /dev/null
+++ b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.cpp
@@ -0,0 +1,92 @@
+//===- 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"
+
+using namespace llvm;
+
+const AMDGPUVariadicMCExpr *
+AMDGPUVariadicMCExpr::create(AMDGPUVariadicKind Kind,
+                             const std::vector<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 << ")";
+}
+
+bool AMDGPUVariadicMCExpr::evaluateAsRelocatableImpl(
+    MCValue &Res, const MCAsmLayout *Layout, const MCFixup *Fixup) const {
+  int64_t total = 0;
+
+  auto Op = [this](int64_t Arg1, int64_t Arg2) -> int64_t {
+    switch (Kind) {
+    default:
+      llvm_unreachable("Unknown AMDGPUVariadicMCExpr kind.");
+    case AGVK_Max:
+      return Arg1 > Arg2 ? Arg1 : Arg2;
+    case AGVK_Or:
+      return (!!Arg1) || (!!Arg2);
+    }
+  };
+
+  for (const MCExpr *Arg : Args) {
+    MCValue ArgRes;
+    if (!Arg->evaluateAsRelocatable(ArgRes, Layout, Fixup))
+      return false;
+    if (!ArgRes.isAbsolute())
+      return false;
+    total = Op(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;
+}
diff --git a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.h b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.h
new file mode 100644
index 00000000000000..acd1dc47934bad
--- /dev/null
+++ b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.h
@@ -0,0 +1,64 @@
+//===- 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/MC/MCExpr.h"
+
+namespace llvm {
+
+class AMDGPUMCExpr : public MCTargetExpr {
+  static bool classof(const MCExpr *E) {
+    return E->getKind() == MCExpr::Target;
+  }
+  void fixELFSymbolsInTLSFixups(MCAssembler &) const override{};
+};
+
+class AMDGPUVariadicMCExpr : public AMDGPUMCExpr {
+public:
+  enum AMDGPUVariadicKind { AGVK_None, AGVK_Or, AGVK_Max };
+
+private:
+  AMDGPUVariadicKind Kind;
+  std::vector<const MCExpr *> Args;
+
+  AMDGPUVariadicMCExpr(AMDGPUVariadicKind Kind,
+                       const std::vector<const MCExpr *> &Args)
+      : Kind(Kind), Args(Args) {
+    assert(Args.size() >= 1 && "Can't take the maximum of 0 expressions.");
+  }
+
+public:
+  static const AMDGPUVariadicMCExpr *
+  create(AMDGPUVariadicKind Kind, const std::vector<const MCExpr *> &Args,
+         MCContext &Ctx);
+
+  static const AMDGPUVariadicMCExpr *
+  createOr(const std::vector<const MCExpr *> &Args, MCContext &Ctx) {
+    return create(AMDGPUVariadicKind::AGVK_Or, Args, Ctx);
+  }
+
+  static const AMDGPUVariadicMCExpr *
+  createMax(const std::vector<const MCExpr *> &Args, MCContext &Ctx) {
+    return create(AMDGPUVariadicKind::AGVK_Max, Args, Ctx);
+  }
+
+  AMDGPUVariadicKind 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;
+};
+
+} // end namespace llvm
+
+#endif // LLVM_LIB_TARGET_AMDGPU_MCTARGETDESC_AMDGPUMCEXPR_H
\ No newline at end of file
diff --git a/llvm/lib/Target/AMDGPU/MCTargetDesc/CMakeLists.txt b/llvm/lib/Target/AMDGPU/MCTargetDesc/CMakeLists.txt
index 5dc76071b0594e..0842a58f794b32 100644
--- a/llvm/lib/Target/AMDGPU/MCTargetDesc/CMakeLists.txt
+++ b/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
diff --git a/llvm/test/MC/AMDGPU/mcexpr_amd.s b/llvm/test/MC/AMDGPU/mcexpr_amd.s
new file mode 100644
index 00000000000000..a201c35e8d2caf
--- /dev/null
+++ b/llvm/test/MC/AMDGPU/mcexpr_amd.s
@@ -0,0 +1,92 @@
+// RUN: llvm-mc -triple amdgcn-amd-amdhsa < %s | FileCheck --check-prefix=ASM %s
+// RUN: llvm-mc -triple amdgcn-amd-amdhsa -filetype=obj < %s > %t
+// RUN: llvm-objdump --syms %t | FileCheck --check-prefix=OBJDUMP %s
+
+// OBJDUMP: SYMBOL TABLE:
+// OBJDUMP-NEXT: 0000000000000000 l       *ABS*  0000000000000000 zero
+// OBJDUMP-NEXT: 0000000000000001 l       *ABS*  0000000000000000 one
+// OBJDUMP-NEXT: 0000000000000002 l       *ABS*  0000000000000000 two
+// OBJDUMP-NEXT: 0000000000000003 l       *ABS*  0000000000000000 three
+// OBJDUMP-NEXT: 0000000000000005 l       *ABS*  0000000000000000 max_expression_all
+// OBJDUMP-NEXT: 0000000000000005 l       *ABS*  0000000000000000 five
+// OBJDUMP-NEXT: 0000000000000004 l       *ABS*  0000000000000000 four
+// OBJDUMP-NEXT: 0000000000000002 l       *ABS*  0000000000000000 max_expression_two
+// OBJDUMP-NEXT: 0000000000000001 l       *ABS*  0000000000000000 max_expression_one
+// OBJDUMP-NEXT: 000000000000000a l       *ABS*  0000000000000000 max_literals
+// OBJDUMP-NEXT: 000000000000000f l       *ABS*  0000000000000000 max_with_max_sym
+// OBJDUMP-NEXT: 000000000000000f l       *ABS*  0000000000000000 max
+// OBJDUMP-NEXT: 0000000000000003 l       *ABS*  0000000000000000 max_with_subexpr
+// OBJDUMP-NEXT: 0000000000000006 l       *ABS*  0000000000000000 max_as_subexpr
+// OBJDUMP-NEXT: 0000000000000005 l       *ABS*  0000000000000000 max_recursive_subexpr
+// OBJDUMP-NEXT: 0000000000000001 l       *ABS*  0000000000000000 or_expression_all
+// OBJDUMP-NEXT: 0000000000000001 l       *ABS*  0000000000000000 or_expression_two
+// OBJDUMP-NEXT: 0000000000000001 l       *ABS*  0000000000000000 or_expression_one
+// OBJDUMP-NEXT: 0000000000000001 l       *ABS*  0000000000000000 or_literals
+// OBJDUMP-NEXT: 0000000000000000 l       *ABS*  0000000000000000 or_false
+// OBJDUMP-NEXT: 0000000000000001 l       *ABS*  0000000000000000 or_with_or_sym
+// OBJDUMP-NEXT: 00000000000000ff l       *ABS*  0000000000000000 or
+// OBJDUMP-NEXT: 0000000000000001 l       *ABS*  0000000000000000 or_with_subexpr
+// OBJDUMP-NEXT: 0000000000000002 l       *ABS*  0000000000000000 or_as_subexpr
+// OBJDUMP-NEXT: 0000000000000001 l       *ABS*  0000000000000000 or_recursive_subexpr
+
+// ASM: .set zero, 0
+// ASM: .set one, 1
+// ASM: .set two, 2
+// ASM: .set three, 3
+
+.set zero, 0
+.set one, 1
+.set two, 2
+.set three, 3
+
+// ASM: .set max_expression_all, max(1, 2, five, 3, four)
+// ASM: .set max_expression_two, 2
+// ASM: .set max_expression_one, 1
+// ASM: .set max_literals, 10
+// ASM: .set max_with_max_sym, max(max, 4, 3, 1, 2)
+
+.set max_expression_all, max(one, two, five, three, four)
+.set max_expression_two, max(one, two)
+.set max_expression_one, max(one)
+.set max_literals, max(1,2,3,4,5,6,7,8,9,10)
+.set max_with_max_sym, max(max, 4, 3, one, two)
+
+// ASM: .set max_with_subexpr, 3
+// ASM: .set max_as_subexpr, 1+(max(4, 3, five))
+// ASM: .set max_recursive_subexpr, max(max(1, four), 3, max_expression_all)
+
+.set max_with_subexpr, max(((one | 3) << 3) / 8)
+.set max_as_subexpr, 1 + max(4, 3, five)
+.set max_recursive_subexpr, max(max(one, four), three, max_expression_all)
+
+// ASM: .set or_expression_all, or(1, 2, five, 3, four)
+// ASM: .set or_expression_two, 1
+// ASM: .set or_expression_one, 1
+// ASM: .set or_literals, 1
+// ASM: .set or_false, 0
+// ASM: .set or_with_or_sym, or(or, 4, 3, 1, 2)
+
+.set or_expression_all, or(one, two, five, three, four)
+.set or_expression_two, or(one, two)
+.set or_expression_one, or(one)
+.set or_literals, or(1,2,3,4,5,6,7,8,9,10)
+.set or_false, or(zero, 0, (2-2), 5 > 6)
+.set or_with_or_sym, or(or, 4, 3, one, two)
+
+// ASM: .set or_with_subexpr, 1
+// ASM: .set or_as_subexpr, 1+(or(4, 3, five))
+// ASM: .set or_recursive_subexpr, or(or(1, four), 3, or_expression_all)
+
+.set or_with_subexpr, or(((one | 3) << 3) / 8)
+.set or_as_subexpr, 1 + or(4, 3, five)
+.set or_recursive_subexpr, or(or(one, four), three, or_expression_all)
+
+// ASM: .set four, 4
+// ASM: .set five, 5
+// ASM: .set max, 15
+// ASM: .set or, 255
+
+.set four, 4
+.set five, 5
+.set max, 0xF
+.set or, 0xFF
diff --git a/llvm/test/MC/AMDGPU/mcexpr_amd_err.s b/llvm/test/MC/AMDGPU/mcexpr_amd_err.s
new file mode 100644
index 00000000000000..ffe1918399a7cc
--- /dev/null
+++ b/llvm/test/MC/AMDGPU/mcexpr_amd_err.s
@@ -0,0 +1,26 @@
+// RUN: not llvm-mc -triple amdgcn-amd-amdhsa %s 2>&1 | FileCheck --check-prefix=ASM %s
+
+// ASM: error: empty max/or expression
+// ASM: error: missing expression
+// ASM: error: unknown token in expression
+// ASM: error: missing expression
+// ASM: error: unexpected token in max/or expression
+// ASM: error: missing expression
+// ASM: error: unknown token in expression
+// ASM: error: missing expression
+// ASM: error: unexpected token in max/or expression
+// ASM: error: missing expression
+
+.set one, 1
+.set two, 2
+.set three, 3
+
+.set max_empty, max()
+.set max_post_aux_comma, max(one,)
+.set max_pre_aux_comma, max(,one)
+.set max_missing_paren, max(two
+.set max_expression_one, max(three, four,
+.set max_expression_one, max(four, five
+
+.set four, 4
+.set five, 5

>From db29bc6761fe4ca2691223e37f3b22a8d01e8efd Mon Sep 17 00:00:00 2001
From: Janek van Oirschot <janek.vanoirschot at amd.com>
Date: Mon, 19 Feb 2024 14:24:08 +0000
Subject: [PATCH 2/2] Apply feedback

---
 .../AMDGPU/AsmParser/AMDGPUAsmParser.cpp      | 12 ++---
 .../AMDGPU/MCTargetDesc/AMDGPUMCExpr.cpp      | 30 ++++++-------
 .../Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.h | 45 ++++++++++---------
 llvm/test/MC/AMDGPU/mcexpr_amd.s              | 10 +++++
 4 files changed, 56 insertions(+), 41 deletions(-)

diff --git a/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp b/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
index c878d9d26988e9..2ad05cfdf9c43f 100644
--- a/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
+++ b/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
@@ -8140,16 +8140,16 @@ void AMDGPUAsmParser::onBeginOfFile() {
 bool AMDGPUAsmParser::parsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) {
   using AGVK = AMDGPUVariadicMCExpr::AMDGPUVariadicKind;
 
-  auto parseVariadicExpr = [&](AGVK Kind, const MCExpr *&res, SMLoc &EndLoc) {
-    std::vector<const MCExpr *> Exprs;
+  auto ParseVariadicExpr = [&](AGVK Kind, const MCExpr *&Result,
+                               SMLoc &EndLoc) {
+    SmallVector<const MCExpr *, 4> Exprs;
     while (true) {
-      if (isToken(AsmToken::RParen)) {
+      if (trySkipToken(AsmToken::RParen)) {
         if (Exprs.empty()) {
           Error(getToken().getLoc(), "empty max/or expression");
           return true;
         }
-        lex();
-        res = AMDGPUVariadicMCExpr::create(Kind, Exprs, getContext());
+        Result = AMDGPUVariadicMCExpr::create(Kind, Exprs, getContext());
         return false;
       }
       const MCExpr *Expr;
@@ -8173,7 +8173,7 @@ bool AMDGPUAsmParser::parsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) {
     if (VK != AGVK::AGVK_None && peekToken().is(AsmToken::LParen)) {
       lex(); // Eat 'max'/'or'
       lex(); // Eat '('
-      return parseVariadicExpr(VK, Res, EndLoc);
+      return ParseVariadicExpr(VK, Res, EndLoc);
     }
   }
   return getParser().parsePrimaryExpr(Res, EndLoc, nullptr);
diff --git a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.cpp b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.cpp
index 3b00de3756d924..013f2244449747 100644
--- a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.cpp
+++ b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.cpp
@@ -18,8 +18,7 @@ using namespace llvm;
 
 const AMDGPUVariadicMCExpr *
 AMDGPUVariadicMCExpr::create(AMDGPUVariadicKind Kind,
-                             const std::vector<const MCExpr *> &Args,
-                             MCContext &Ctx) {
+                             ArrayRef<const MCExpr *> Args, MCContext &Ctx) {
   return new (Ctx) AMDGPUVariadicMCExpr(Kind, Args);
 }
 
@@ -41,9 +40,9 @@ void AMDGPUVariadicMCExpr::printImpl(raw_ostream &OS,
     OS << "max(";
     break;
   }
-  for (auto it = Args.begin(); it != Args.end(); ++it) {
-    (*it)->print(OS, MAI, /*InParens=*/false);
-    if ((it + 1) != Args.end())
+  for (auto It = Args.begin(); It != Args.end(); ++It) {
+    (*It)->print(OS, MAI, /*InParens=*/false);
+    if ((It + 1) != Args.end())
       OS << ", ";
   }
   OS << ")";
@@ -51,36 +50,37 @@ void AMDGPUVariadicMCExpr::printImpl(raw_ostream &OS,
 
 bool AMDGPUVariadicMCExpr::evaluateAsRelocatableImpl(
     MCValue &Res, const MCAsmLayout *Layout, const MCFixup *Fixup) const {
-  int64_t total = 0;
+  int64_t Total = INT64_MIN;
 
   auto Op = [this](int64_t Arg1, int64_t Arg2) -> int64_t {
     switch (Kind) {
     default:
       llvm_unreachable("Unknown AMDGPUVariadicMCExpr kind.");
     case AGVK_Max:
-      return Arg1 > Arg2 ? Arg1 : Arg2;
+      return std::max(Arg1, Arg2);
     case AGVK_Or:
-      return (!!Arg1) || (!!Arg2);
+      return Arg1 || Arg2;
     }
   };
 
   for (const MCExpr *Arg : Args) {
     MCValue ArgRes;
-    if (!Arg->evaluateAsRelocatable(ArgRes, Layout, Fixup))
+    if (!Arg->evaluateAsRelocatable(ArgRes, Layout, Fixup) ||
+        !ArgRes.isAbsolute())
       return false;
-    if (!ArgRes.isAbsolute())
-      return false;
-    total = Op(total, ArgRes.getConstant());
+
+    if (Total == INT64_MIN)
+      Total = ArgRes.getConstant();
+    Total = Op(Total, ArgRes.getConstant());
   }
 
-  Res = MCValue::get(total);
+  Res = MCValue::get(Total);
   return true;
 }
 
 void AMDGPUVariadicMCExpr::visitUsedExpr(MCStreamer &Streamer) const {
-  for (const MCExpr *Arg : Args) {
+  for (const MCExpr *Arg : Args)
     Streamer.visitUsedExpr(*Arg);
-  }
 }
 
 MCFragment *AMDGPUVariadicMCExpr::findAssociatedFragment() const {
diff --git a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.h b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.h
index acd1dc47934bad..a1657adf8ca7c6 100644
--- a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.h
+++ b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCExpr.h
@@ -9,43 +9,44 @@
 #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 {
 
-class AMDGPUMCExpr : public MCTargetExpr {
-  static bool classof(const MCExpr *E) {
-    return E->getKind() == MCExpr::Target;
-  }
-  void fixELFSymbolsInTLSFixups(MCAssembler &) const override{};
-};
-
-class AMDGPUVariadicMCExpr : public AMDGPUMCExpr {
+/// AMDGPU target specific variadic MCExpr operations.
+///
+/// Takes in a minimum of 1 argument to be used with an operation. The supported
+/// operations are:
+///   - (logic) or
+///   - max
+///
+class AMDGPUVariadicMCExpr : public MCTargetExpr {
 public:
   enum AMDGPUVariadicKind { AGVK_None, AGVK_Or, AGVK_Max };
 
 private:
   AMDGPUVariadicKind Kind;
-  std::vector<const MCExpr *> Args;
+  SmallVector<const MCExpr *, 2> Args;
 
-  AMDGPUVariadicMCExpr(AMDGPUVariadicKind Kind,
-                       const std::vector<const MCExpr *> &Args)
+  AMDGPUVariadicMCExpr(AMDGPUVariadicKind Kind, ArrayRef<const MCExpr *> Args)
       : Kind(Kind), Args(Args) {
-    assert(Args.size() >= 1 && "Can't take the maximum of 0 expressions.");
+    assert(Args.size() >= 1 && "Needs a minimum of one expression.");
   }
 
 public:
-  static const AMDGPUVariadicMCExpr *
-  create(AMDGPUVariadicKind Kind, const std::vector<const MCExpr *> &Args,
-         MCContext &Ctx);
+  static const AMDGPUVariadicMCExpr *create(AMDGPUVariadicKind Kind,
+                                            ArrayRef<const MCExpr *> Args,
+                                            MCContext &Ctx);
 
-  static const AMDGPUVariadicMCExpr *
-  createOr(const std::vector<const MCExpr *> &Args, MCContext &Ctx) {
+  static const AMDGPUVariadicMCExpr *createOr(ArrayRef<const MCExpr *> Args,
+                                              MCContext &Ctx) {
     return create(AMDGPUVariadicKind::AGVK_Or, Args, Ctx);
   }
 
-  static const AMDGPUVariadicMCExpr *
-  createMax(const std::vector<const MCExpr *> &Args, MCContext &Ctx) {
+  static const AMDGPUVariadicMCExpr *createMax(ArrayRef<const MCExpr *> Args,
+                                               MCContext &Ctx) {
     return create(AMDGPUVariadicKind::AGVK_Max, Args, Ctx);
   }
 
@@ -57,8 +58,12 @@ class AMDGPUVariadicMCExpr : public AMDGPUMCExpr {
                                  const MCFixup *Fixup) const override;
   void visitUsedExpr(MCStreamer &Streamer) const override;
   MCFragment *findAssociatedFragment() const override;
+  static bool classof(const MCExpr *E) {
+    return E->getKind() == MCExpr::Target;
+  }
+  void fixELFSymbolsInTLSFixups(MCAssembler &) const override{};
 };
 
 } // end namespace llvm
 
-#endif // LLVM_LIB_TARGET_AMDGPU_MCTARGETDESC_AMDGPUMCEXPR_H
\ No newline at end of file
+#endif // LLVM_LIB_TARGET_AMDGPU_MCTARGETDESC_AMDGPUMCEXPR_H
diff --git a/llvm/test/MC/AMDGPU/mcexpr_amd.s b/llvm/test/MC/AMDGPU/mcexpr_amd.s
index a201c35e8d2caf..0ebcbc08363a8a 100644
--- a/llvm/test/MC/AMDGPU/mcexpr_amd.s
+++ b/llvm/test/MC/AMDGPU/mcexpr_amd.s
@@ -15,6 +15,9 @@
 // OBJDUMP-NEXT: 000000000000000a l       *ABS*  0000000000000000 max_literals
 // OBJDUMP-NEXT: 000000000000000f l       *ABS*  0000000000000000 max_with_max_sym
 // OBJDUMP-NEXT: 000000000000000f l       *ABS*  0000000000000000 max
+// OBJDUMP-NEXT: ffffffffffffffff l       *ABS*  0000000000000000 neg_one
+// OBJDUMP-NEXT: ffffffffffffffff l       *ABS*  0000000000000000 max_neg_numbers
+// OBJDUMP-NEXT: ffffffffffffffff l       *ABS*  0000000000000000 max_neg_number
 // OBJDUMP-NEXT: 0000000000000003 l       *ABS*  0000000000000000 max_with_subexpr
 // OBJDUMP-NEXT: 0000000000000006 l       *ABS*  0000000000000000 max_as_subexpr
 // OBJDUMP-NEXT: 0000000000000005 l       *ABS*  0000000000000000 max_recursive_subexpr
@@ -51,6 +54,13 @@
 .set max_literals, max(1,2,3,4,5,6,7,8,9,10)
 .set max_with_max_sym, max(max, 4, 3, one, two)
 
+// ASM: .set max_neg_numbers, -1
+// ASM: .set max_neg_number, -1
+
+.set neg_one, -1
+.set max_neg_numbers, max(-5, -4, -3, -2, neg_one)
+.set max_neg_number, max(neg_one)
+
 // ASM: .set max_with_subexpr, 3
 // ASM: .set max_as_subexpr, 1+(max(4, 3, five))
 // ASM: .set max_recursive_subexpr, max(max(1, four), 3, max_expression_all)



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