[llvm] [TableGen][DecoderEmitter] Add option to emit type-specialized code (PR #146593)

[Sergei Barannikov via llvm-commits]

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@@ -2106,99 +2192,196 @@ populateInstruction(const CodeGenTarget &Target, const Record &EncodingDef,
   return Bits.getNumBits();
 }
 
-// emitFieldFromInstruction - Emit the templated helper function
-// fieldFromInstruction().
-// On Windows we make sure that this function is not inlined when
-// using the VS compiler. It has a bug which causes the function
-// to be optimized out in some circumstances. See llvm.org/pr38292
-static void emitFieldFromInstruction(formatted_raw_ostream &OS) {
-  OS << R"(
-// Helper functions for extracting fields from encoded instructions.
-// InsnType must either be integral or an APInt-like object that must:
-// * be default-constructible and copy-constructible
-// * Support extractBitsAsZExtValue(numBits, startBit)
-// * Support the ~, &, ==, and != operators with other objects of the same type
-// * Support the != and bitwise & with uint64_t
-template <typename InsnType>
+// Emit the templated helper function fieldFromInstruction().
+//
+// On Windows we make sure that this function is not inlined when using the VS
+// compiler. It has a bug which causes the function to be optimized out in some
+// circumstances. See llvm.org/pr38292
+//
+// There are 4 variants of this function that can be generated under different
+// conditions:
+//
+// 1. Integer types (for non-templated code when using integer types and when
+//                   generating templated code).
+// 2. bitset types (for non-templated code with bitset type).
+// 3. APInt type (for variable length instructions).
+// 4. Non-Integer `InsnType` (when generating templated code)
+
+static void emitFieldFromInstruction(formatted_raw_ostream &OS,
+                                     bool GenerateIntType,
+                                     bool GenerateBitsetType,
+                                     bool GenerateAPIntType,
+                                     bool GenerateTemplateType) {
+  if (GenerateIntType) {
+    OS << R"(
+// Helper macro to disable inlining of `fieldFromInstruction` for integer types.
 #if defined(_MSC_VER) && !defined(__clang__)
-__declspec(noinline)
+#define DEC_EMIT_NO_INLINE __declspec(noinline)
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s-barannikov wrote:

Adding the macro doesn't seem necessary?

https://github.com/llvm/llvm-project/pull/146593