[llvm] [TableGen] Bug fix for tied optional operands resolution (PR #83588)

[Alfie Richards via llvm-commits]

https://github.com/AlfieRichardsArm created https://github.com/llvm/llvm-project/pull/83588

This fixes tied operand resolution when there are optional operands before it.

>From 0d58b59df8b49e03be865c3e1768c5740685d534 Mon Sep 17 00:00:00 2001
From: Alfie Richards <alfie.richards at arm.com>
Date: Fri, 1 Mar 2024 15:30:40 +0000
Subject: [PATCH] [TableGen] Bug fix for tied optional operands resolution

---
 llvm/utils/TableGen/AsmMatcherEmitter.cpp | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/llvm/utils/TableGen/AsmMatcherEmitter.cpp b/llvm/utils/TableGen/AsmMatcherEmitter.cpp
index febd96086df27b..e0602a71707a73 100644
--- a/llvm/utils/TableGen/AsmMatcherEmitter.cpp
+++ b/llvm/utils/TableGen/AsmMatcherEmitter.cpp
@@ -1986,9 +1986,9 @@ emitConvertFuncs(CodeGenTarget &Target, StringRef ClassName,
   }
   CvtOS << "  assert(Kind < CVT_NUM_SIGNATURES && \"Invalid signature!\");\n";
   CvtOS << "  const uint8_t *Converter = ConversionTable[Kind];\n";
-  CvtOS << "  unsigned OpIdx;\n";
   CvtOS << "  Inst.setOpcode(Opcode);\n";
   CvtOS << "  for (const uint8_t *p = Converter; *p; p += 2) {\n";
+  CvtOS << "    unsigned OpIdx;\n";
   if (HasOptionalOperands) {
     // When optional operands are involved, formal and actual operand indices
     // may differ. Map the former to the latter by subtracting the number of
@@ -1999,16 +1999,17 @@ emitConvertFuncs(CodeGenTarget &Target, StringRef ClassName,
   }
   CvtOS << "    switch (*p) {\n";
   CvtOS << "    default: llvm_unreachable(\"invalid conversion entry!\");\n";
-  CvtOS << "    case CVT_Reg:\n";
+  CvtOS << "    case CVT_Reg:{\n";
   CvtOS << "      static_cast<" << TargetOperandClass
         << " &>(*Operands[OpIdx]).addRegOperands(Inst, 1);\n";
   CvtOS << "      break;\n";
+  CvtOS << "    }\n";
   CvtOS << "    case CVT_Tied: {\n";
-  CvtOS << "      assert(OpIdx < (size_t)(std::end(TiedAsmOperandTable) -\n";
+  CvtOS << "      assert(*(p + 1) < (size_t)(std::end(TiedAsmOperandTable) -\n";
   CvtOS
       << "                              std::begin(TiedAsmOperandTable)) &&\n";
   CvtOS << "             \"Tied operand not found\");\n";
-  CvtOS << "      unsigned TiedResOpnd = TiedAsmOperandTable[OpIdx][0];\n";
+  CvtOS << "      unsigned TiedResOpnd = TiedAsmOperandTable[*(p + 1)][0];\n";
   CvtOS << "      if (TiedResOpnd != (uint8_t)-1)\n";
   CvtOS << "        Inst.addOperand(Inst.getOperand(TiedResOpnd));\n";
   CvtOS << "      break;\n";