[llvm] [TableGen][NFC] Factor early-out range check. (PR #123645)

[Jason Eckhardt via llvm-commits]

https://github.com/nvjle updated https://github.com/llvm/llvm-project/pull/123645

>From d919d4d28a2d2343abf68d14ea908d514986ebbf Mon Sep 17 00:00:00 2001
From: Jason Eckhardt <jeckhardt at nvidia.com>
Date: Mon, 20 Jan 2025 10:35:06 -0600
Subject: [PATCH 1/2] [TableGen][NFC] Factor early-out range check.

Combine the EarlyOut and IsContiguous range check.
Also avoid "comparison is always false" warnings in emitted code when
the lower-bound check is against 0.
---
 .../utils/TableGen/SearchableTableEmitter.cpp | 41 ++++++++-----------
 1 file changed, 18 insertions(+), 23 deletions(-)

diff --git a/llvm/utils/TableGen/SearchableTableEmitter.cpp b/llvm/utils/TableGen/SearchableTableEmitter.cpp
index 38b6f2b3951375..5788e6eb56a683 100644
--- a/llvm/utils/TableGen/SearchableTableEmitter.cpp
+++ b/llvm/utils/TableGen/SearchableTableEmitter.cpp
@@ -392,37 +392,32 @@ void SearchableTableEmitter::emitLookupFunction(const GenericTable &Table,
     }
   }
 
-  if (IsContiguous) {
+  if (Index.EarlyOut || IsContiguous) {
     const GenericField &Field = Index.Fields[0];
     std::string FirstRepr = primaryRepresentation(
         Index.Loc, Field, IndexRows[0]->getValueInit(Field.Name));
     std::string LastRepr = primaryRepresentation(
         Index.Loc, Field, IndexRows.back()->getValueInit(Field.Name));
-    OS << "  if ((" << Field.Name << " < " << FirstRepr << ") ||\n";
-    OS << "      (" << Field.Name << " > " << LastRepr << "))\n";
-    OS << "    return nullptr;\n";
-    OS << "  auto Table = ArrayRef(" << IndexName << ");\n";
-    OS << "  size_t Idx = " << Index.Fields[0].Name << " - " << FirstRepr
-       << ";\n";
-    OS << "  return ";
-    if (IsPrimary)
-      OS << "&Table[Idx]";
+    if (getNumericKey(Index, IndexRows[0]) == 0)
+      OS << "  if (";
     else
-      OS << "&" << Table.Name << "[Table[Idx]._index]";
-    OS << ";\n";
-    OS << "}\n";
-    return;
-  }
-
-  if (Index.EarlyOut) {
-    const GenericField &Field = Index.Fields[0];
-    std::string FirstRepr = primaryRepresentation(
-        Index.Loc, Field, IndexRows[0]->getValueInit(Field.Name));
-    std::string LastRepr = primaryRepresentation(
-        Index.Loc, Field, IndexRows.back()->getValueInit(Field.Name));
-    OS << "  if ((" << Field.Name << " < " << FirstRepr << ") ||\n";
+      OS << "  if ((" << Field.Name << " < " << FirstRepr << ") ||\n";
     OS << "      (" << Field.Name << " > " << LastRepr << "))\n";
     OS << "    return nullptr;\n\n";
+
+    if (IsContiguous) {
+      OS << "  auto Table = ArrayRef(" << IndexName << ");\n";
+      OS << "  size_t Idx = " << Index.Fields[0].Name << " - " << FirstRepr
+         << ";\n";
+      OS << "  return ";
+      if (IsPrimary)
+        OS << "&Table[Idx]";
+      else
+        OS << "&" << Table.Name << "[Table[Idx]._index]";
+      OS << ";\n";
+      OS << "}\n";
+      return;
+    }
   }
 
   OS << "  struct KeyType {\n";

>From 5a5e07274b4227b6089d0f50ef87f1ca5ab59790 Mon Sep 17 00:00:00 2001
From: Jason Eckhardt <jeckhardt at nvidia.com>
Date: Mon, 20 Jan 2025 14:38:24 -0600
Subject: [PATCH 2/2] wip

---
 .../utils/TableGen/SearchableTableEmitter.cpp | 20 +++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/llvm/utils/TableGen/SearchableTableEmitter.cpp b/llvm/utils/TableGen/SearchableTableEmitter.cpp
index 5788e6eb56a683..2ee996bffb3813 100644
--- a/llvm/utils/TableGen/SearchableTableEmitter.cpp
+++ b/llvm/utils/TableGen/SearchableTableEmitter.cpp
@@ -211,20 +211,21 @@ class SearchableTableEmitter {
 // known, return that numeric value.
 int64_t SearchableTableEmitter::getNumericKey(const SearchIndex &Index,
                                               const Record *Rec) {
-  assert(Index.Fields.size() == 1);
+  const GenericField &Field = Index.Fields[0];
 
   // To be consistent with compareBy and primaryRepresentation elsewhere,
   // we check for IsInstruction before Enum-- these fields are not exclusive.
-  if (Index.Fields[0].IsInstruction) {
-    const Record *TheDef = Rec->getValueAsDef(Index.Fields[0].Name);
+  if (Field.IsInstruction) {
+    const Record *TheDef = Rec->getValueAsDef(Field.Name);
     return Target->getInstrIntValue(TheDef);
   }
-  if (Index.Fields[0].Enum) {
-    const Record *EnumEntry = Rec->getValueAsDef(Index.Fields[0].Name);
-    return Index.Fields[0].Enum->EntryMap[EnumEntry]->second;
+  if (Field.Enum) {
+    const Record *EnumEntry = Rec->getValueAsDef(Field.Name);
+    return Field.Enum->EntryMap[EnumEntry]->second;
   }
+  assert(isa<BitsRecTy>(Field.RecType) && "unexpected field type");
 
-  return getInt(Rec, Index.Fields[0].Name);
+  return getInt(Rec, Field.Name);
 }
 
 /// Less-than style comparison between \p LHS and \p RHS according to the
@@ -405,10 +406,9 @@ void SearchableTableEmitter::emitLookupFunction(const GenericTable &Table,
     OS << "      (" << Field.Name << " > " << LastRepr << "))\n";
     OS << "    return nullptr;\n\n";
 
-    if (IsContiguous) {
+    if (IsContiguous && !Index.EarlyOut) {
       OS << "  auto Table = ArrayRef(" << IndexName << ");\n";
-      OS << "  size_t Idx = " << Index.Fields[0].Name << " - " << FirstRepr
-         << ";\n";
+      OS << "  size_t Idx = " << Field.Name << " - " << FirstRepr << ";\n";
       OS << "  return ";
       if (IsPrimary)
         OS << "&Table[Idx]";