[llvm] [NFC][LLVM][TableGen] Use `decodeULEB128` for `OPC_SoftFail` emission (PR #136220)

[Rahul Joshi via llvm-commits]

https://github.com/jurahul created https://github.com/llvm/llvm-project/pull/136220

- Use `decodeULEB128` to decode +ve/-ve mask in OPC_SoftFail case.
- Use current I/E iterators as inputs to `decodeULEB128`.

>From fbee99a9cff146105c8d5c1cf602f71cc1c92f8f Mon Sep 17 00:00:00 2001
From: Rahul Joshi <rjoshi at nvidia.com>
Date: Thu, 17 Apr 2025 15:59:56 -0700
Subject: [PATCH] [NFC][LLVM][TableGen] Use `decodeULEB128` for `OPC_SoftFail`
 emission

- Use `decodeULEB128` to decode +ve/-ve mask in OPC_SoftFail case.
- Use current I/E iterators as inputs to `decodeULEB128`.
---
 llvm/utils/TableGen/DecoderEmitter.cpp | 39 ++++++++++----------------
 1 file changed, 15 insertions(+), 24 deletions(-)

diff --git a/llvm/utils/TableGen/DecoderEmitter.cpp b/llvm/utils/TableGen/DecoderEmitter.cpp
index 9c6015cc24576..7961e19a11eac 100644
--- a/llvm/utils/TableGen/DecoderEmitter.cpp
+++ b/llvm/utils/TableGen/DecoderEmitter.cpp
@@ -849,8 +849,7 @@ void DecoderEmitter::emitTable(formatted_raw_ostream &OS, DecoderTable &Table,
 
       // ULEB128 encoded start value.
       const char *ErrMsg = nullptr;
-      unsigned Start = decodeULEB128(Table.data() + Pos + 1, nullptr,
-                                     Table.data() + Table.size(), &ErrMsg);
+      unsigned Start = decodeULEB128(&*I, nullptr, &*E, &ErrMsg);
       assert(ErrMsg == nullptr && "ULEB128 value too large!");
       emitULEB128(I, OS);
 
@@ -904,8 +903,7 @@ void DecoderEmitter::emitTable(formatted_raw_ostream &OS, DecoderTable &Table,
       ++I;
       // Decode the Opcode value.
       const char *ErrMsg = nullptr;
-      unsigned Opc = decodeULEB128(Table.data() + Pos + 1, nullptr,
-                                   Table.data() + Table.size(), &ErrMsg);
+      unsigned Opc = decodeULEB128(&*I, nullptr, &*E, &ErrMsg);
       assert(ErrMsg == nullptr && "ULEB128 value too large!");
 
       OS << Indent << "MCD::OPC_" << (IsTry ? "Try" : "") << "Decode, ";
@@ -935,30 +933,23 @@ void DecoderEmitter::emitTable(formatted_raw_ostream &OS, DecoderTable &Table,
     case MCD::OPC_SoftFail: {
       ++I;
       OS << Indent << "MCD::OPC_SoftFail";
-      // Positive mask
-      uint64_t Value = 0;
-      unsigned Shift = 0;
-      do {
-        OS << ", " << (unsigned)*I;
-        Value += ((uint64_t)(*I & 0x7f)) << Shift;
-        Shift += 7;
-      } while (*I++ >= 128);
-      if (Value > 127) {
+      // Decode the positive mask.
+      const char *ErrMsg = nullptr;
+      uint64_t PositiveMask = decodeULEB128(&*I, nullptr, &*E, &ErrMsg);
+      assert(ErrMsg == nullptr && "ULEB128 value too large!");
+      emitULEB128(I, OS);
+      if (PositiveMask > 127) {
         OS << " /* 0x";
-        OS.write_hex(Value);
+        OS.write_hex(PositiveMask);
         OS << " */";
       }
-      // Negative mask
-      Value = 0;
-      Shift = 0;
-      do {
-        OS << ", " << (unsigned)*I;
-        Value += ((uint64_t)(*I & 0x7f)) << Shift;
-        Shift += 7;
-      } while (*I++ >= 128);
-      if (Value > 127) {
+      // Decode the negative mask.
+      uint64_t NegativeMask = decodeULEB128(&*I, nullptr, &*E, &ErrMsg);
+      assert(ErrMsg == nullptr && "ULEB128 value too large!");
+      emitULEB128(I, OS);
+      if (NegativeMask > 127) {
         OS << " /* 0x";
-        OS.write_hex(Value);
+        OS.write_hex(NegativeMask);
         OS << " */";
       }
       OS << ",\n";