[llvm] [TableGen][DecoderEmitter] Remove no longer needed MaxFilterWidth (NFC) (PR #155382)

[Sergei Barannikov via llvm-commits]

https://github.com/s-barannikov created https://github.com/llvm/llvm-project/pull/155382

11c61581 made the variable redundant.
Also remove `Target`, which is apparently unused.

>From 8490a196e547449167b6b6b22a899f2a2847fe79 Mon Sep 17 00:00:00 2001
From: Sergei Barannikov <barannikov88 at gmail.com>
Date: Tue, 26 Aug 2025 12:19:16 +0300
Subject: [PATCH] [TableGen][DecoderEmitter] Remove MaxFilterWidth variable

It is no longer needed after 11c61581.
Also remove `Target`, which is apparently unused.
---
 llvm/utils/TableGen/DecoderEmitter.cpp | 21 ++++-----------------
 1 file changed, 4 insertions(+), 17 deletions(-)

diff --git a/llvm/utils/TableGen/DecoderEmitter.cpp b/llvm/utils/TableGen/DecoderEmitter.cpp
index 885cd8a7d428f..9105d24f66d6d 100644
--- a/llvm/utils/TableGen/DecoderEmitter.cpp
+++ b/llvm/utils/TableGen/DecoderEmitter.cpp
@@ -483,12 +483,6 @@ class FilterChooser {
   // Links to the FilterChooser above us in the decoding tree.
   const FilterChooser *Parent;
 
-  /// Some targets (ARM) specify more encoding bits in Inst that Size allows.
-  /// This field allows us to ignore the extra bits.
-  unsigned MaxFilterWidth;
-
-  const CodeGenTarget &Target;
-
   /// If the selected filter matches multiple encodings, then this is the
   /// starting position and the width of the filtered range.
   unsigned StartBit;
@@ -522,16 +516,12 @@ class FilterChooser {
 public:
   /// Constructs a top-level filter chooser.
   FilterChooser(ArrayRef<InstructionEncoding> Encodings,
-                ArrayRef<unsigned> EncodingIDs, unsigned MaxFilterWidth,
-                const CodeGenTarget &Target)
-      : Encodings(Encodings), EncodingIDs(EncodingIDs), Parent(nullptr),
-        MaxFilterWidth(MaxFilterWidth), Target(Target) {
+                ArrayRef<unsigned> EncodingIDs)
+      : Encodings(Encodings), EncodingIDs(EncodingIDs), Parent(nullptr) {
     // Sort encoding IDs once.
     stable_sort(this->EncodingIDs, LessEncodingIDByWidth(Encodings));
     // Filter width is the width of the smallest encoding.
     unsigned FilterWidth = Encodings[this->EncodingIDs.front()].getBitWidth();
-    // Cap it as necessary.
-    FilterWidth = std::min(FilterWidth, MaxFilterWidth);
     FilterBits = KnownBits(FilterWidth);
     doFilter();
   }
@@ -540,15 +530,12 @@ class FilterChooser {
   FilterChooser(ArrayRef<InstructionEncoding> Encodings,
                 ArrayRef<unsigned> EncodingIDs, const KnownBits &FilterBits,
                 const FilterChooser &Parent)
-      : Encodings(Encodings), EncodingIDs(EncodingIDs), Parent(&Parent),
-        MaxFilterWidth(Parent.MaxFilterWidth), Target(Parent.Target) {
+      : Encodings(Encodings), EncodingIDs(EncodingIDs), Parent(&Parent) {
     // Inferior filter choosers are created from sorted array of encoding IDs.
     assert(is_sorted(EncodingIDs, LessEncodingIDByWidth(Encodings)));
     assert(!FilterBits.hasConflict() && "Broken filter");
     // Filter width is the width of the smallest encoding.
     unsigned FilterWidth = Encodings[EncodingIDs.front()].getBitWidth();
-    // Cap it as necessary.
-    FilterWidth = std::min(FilterWidth, MaxFilterWidth);
     this->FilterBits = FilterBits.anyext(FilterWidth);
     doFilter();
   }
@@ -2562,7 +2549,7 @@ namespace {
     auto [DecoderNamespace, HwModeID, Size] = Key;
     const unsigned BitWidth = IsVarLenInst ? MaxInstLen : 8 * Size;
     // Emit the decoder for this (namespace, hwmode, width) combination.
-    FilterChooser FC(Encodings, EncodingIDs, BitWidth, Target);
+    FilterChooser FC(Encodings, EncodingIDs);
 
     // The decode table is cleared for each top level decoder function. The
     // predicates and decoders themselves, however, are shared across all