[mips][ias] Handle more complicated expressions for memory operands

[sdardis]

Summary

This patch teaches ias for mips to handle expressions such as
(8*4)+(8*31)($sp). Such expression typically occur from the expansion
of multiple macro definitions.

This partially resolves PR/30383.

[sdardis]

Whitespace, variable name changed.

[vkalintiris]

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

4447–4453 ↗

(On Diff #71652)

We should test the comparison/equality operators in MC/Mips/memory-offsets.s as well. Can you check that we follow the GNU assembler behaviour for these?

[sdardis]

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

4447–4453 ↗

(On Diff #71652)

I remember why I didn't test them in memory-offsets.s now. IAS will resolve the result of the comparison to '1' or '0'. GAS behaves oddly and gives 0 or -1. Given the differences, I think I should drop them altogether as I'm struggling to comprehend why someone would use a relational operator in a memory offset.

[sdardis]

Removed comparison operator handling.

[vkalintiris]

LGTM.

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

4447–4453 ↗

(On Diff #71652)

I think we should drop them too. Maybe we should add a comment at the top of the switch statement to remember the difference.

[sdardis]

Thanks for the review.

llvm/trunk/lib/Target/Mips/AsmParser/MipsAsmParser.cpp

if (Tok.isNot(AsmToken::LParen)) {
         // Zero register assumed, add a memory operand with ZERO as its base.
         // "Base" will be managed by k_Memory.
         auto Base = MipsOperand::createGPRReg(
             0, "0", getContext().getRegisterInfo(), S, E, *this);
         Operands.push_back(
             MipsOperand::CreateMem(std::move(Base), IdVal, S, E, *this));
         return MatchOperand_Success;
       }
-      Error(Parser.getTok().getLoc(), "'(' expected");
+      MCBinaryExpr::Opcode Opcode;
+      // GAS and LLVM treat comparison operators different. GAS will generate -1
+      // or 0, while LLVM will generate 0 or 1. Since a comparsion operator is
+      // highly unlikely to be found in a memory offset expression, we don't
+      // handle them.
+      switch (Tok.getKind()) {
+      case AsmToken::Plus:
+        Opcode = MCBinaryExpr::Add;
+        Parser.Lex();
+        break;
+      case AsmToken::Minus:
+        Opcode = MCBinaryExpr::Sub;
+        Parser.Lex();
+        break;
+      case AsmToken::Star:
+        Opcode = MCBinaryExpr::Mul;
+        Parser.Lex();
+        break;
+      case AsmToken::Pipe:
+        Opcode = MCBinaryExpr::Or;
+        Parser.Lex();
+        break;
+      case AsmToken::Amp:
+        Opcode = MCBinaryExpr::And;
+        Parser.Lex();
+        break;
+      case AsmToken::LessLess:
+        Opcode = MCBinaryExpr::Shl;
+        Parser.Lex();
+        break;
+      case AsmToken::GreaterGreater:
+        Opcode = MCBinaryExpr::LShr;
+        Parser.Lex();
+        break;
+      case AsmToken::Caret:
+        Opcode = MCBinaryExpr::Xor;
+        Parser.Lex();
+        break;
+      case AsmToken::Slash:
+        Opcode = MCBinaryExpr::Div;
+        Parser.Lex();
+        break;
+      case AsmToken::Percent:
+        Opcode = MCBinaryExpr::Mod;
+        Parser.Lex();
+        break;
+      default:
+        Error(Parser.getTok().getLoc(), "'(' or expression expected");
+        return MatchOperand_ParseFail;
+      }
+      const MCExpr * NextExpr;
+      if (getParser().parseExpression(NextExpr))
         return MatchOperand_ParseFail;
+      IdVal = MCBinaryExpr::create(Opcode, IdVal, NextExpr, getContext());
     }
 
     Parser.Lex(); // Eat the '(' token.
   }
 
   Res = parseAnyRegister(Operands);
   if (Res != MatchOperand_Success)
     return Res;

llvm/trunk/test/MC/Mips/memory-offsets.s

+# RUN: llvm-mc -arch=mips -mcpu=mips32 -show-encoding %s | FileCheck %s
+
+# Check that parseMemOperand handles expressions such as <int>, (<int>),
+# <expr>, <expr> op <expr>, (<expr>) op (<expr>).
+
+    .global __start
+    .ent    __start
+__start:
+    lw $31, ($29)                       # CHECK: lw  $ra, 0($sp)      # encoding: [0x8f,0xbf,0x00,0x00]
+    lw $31, 0($29)                      # CHECK: lw  $ra, 0($sp)      # encoding: [0x8f,0xbf,0x00,0x00]
+    lw $31, (8)($29)                    # CHECK: lw  $ra, 8($sp)      # encoding: [0x8f,0xbf,0x00,0x08]
+    lw $31, 3 + (4 * 8)($29)            # CHECK: lw  $ra, 35($sp)     # encoding: [0x8f,0xbf,0x00,0x23]
+    lw $31, (8 + 8)($29)                # CHECK: lw  $ra, 16($sp)     # encoding: [0x8f,0xbf,0x00,0x10]
+    lw $31, (8 << 4)($29)               # CHECK: lw  $ra, 128($sp)    # encoding: [0x8f,0xbf,0x00,0x80]
+    lw $31, (32768 >> 2)($29)           # CHECK: lw  $ra, 8192($sp)   # encoding: [0x8f,0xbf,0x20,0x00]
+    lw $31, 32768 >> 2($29)             # CHECK: lw  $ra, 8192($sp)   # encoding: [0x8f,0xbf,0x20,0x00]
+    lw $31, 2 << 3($29)                 # CHECK: lw  $ra, 16($sp)     # encoding: [0x8f,0xbf,0x00,0x10]
+    lw $31, (2 << 3)($29)               # CHECK: lw  $ra, 16($sp)     # encoding: [0x8f,0xbf,0x00,0x10]
+    lw $31, 4 - (4 * 8)($29)            # CHECK: lw  $ra, -28($sp)    # encoding: [0x8f,0xbf,0xff,0xe4]
+    lw $31, 4 | 8 ($29)                 # CHECK: lw  $ra, 12($sp)     # encoding: [0x8f,0xbf,0x00,0x0c]
+    lw $31, 4 || 8 ($29)                # CHECK: lw  $ra, 1($sp)      # encoding: [0x8f,0xbf,0x00,0x01]
+    lw $31, 8 & 8 ($29)                 # CHECK: lw  $ra, 8($sp)      # encoding: [0x8f,0xbf,0x00,0x08]
+    lw $31, (8 * 4) ^ (8 * 31)($29)     # CHECK: lw  $ra, 216($sp)    # encoding: [0x8f,0xbf,0x00,0xd8]
+    lw $31, (8 * 4) / (8 * 31)($29)     # CHECK: lw  $ra, 0($sp)      # encoding: [0x8f,0xbf,0x00,0x00]
+    lw $31, (8 * 4) % (8 * 31)($29)     # CHECK: lw  $ra, 32($sp)     # encoding: [0x8f,0xbf,0x00,0x20]
+    lw $31, (8 * 4) % (8)($29)          # CHECK: lw  $ra, 0($sp)      # encoding: [0x8f,0xbf,0x00,0x00]
+    lw $31, (8 * 4) + (8 * 31) ($29)    # CHECK: lw  $ra, 280($sp)    # encoding: [0x8f,0xbf,0x01,0x18]
+    lw $31, (8*4) + (8*31) + (8*32 + __start) ($29) # CHECK:  lui $ra, %hi((248+((8*32)+__start))+32) # encoding: [0x3c,0x1f,A,A]
+                                                    # CHECK:                                #   fixup A - offset: 0, value: %hi((248+((8*32)+__start))+32), kind: fixup_Mips_HI16
+                                                    # CHECK:  addu  $ra, $ra, $sp           # encoding: [0x03,0xfd,0xf8,0x21]
+                                                    # CHECK:  lw  $ra, %lo((248+((8*32)+__start))+32)($ra) # encoding: [0x8f,0xff,A,A]
+                                                    # CHECK:                                #   fixup A - offset: 0, value: %lo((248+((8*32)+__start))+32), kind: fixup_Mips_LO16
+    .end __start