[llvm] [X86] Support 2nd EVEX compression described in X86CompressEVEX.cpp (PR #77202)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-x86

Author: Shengchen Kan (KanRobert)

<details>
<summary>Changes</summary>

Promoted instruction (EVEX) -> pre-promotion instruction (legacy/VEX)


---
Full diff: https://github.com/llvm/llvm-project/pull/77202.diff


1 Files Affected:

- (modified) llvm/utils/TableGen/X86CompressEVEXTablesEmitter.cpp (+6-2) 


``````````diff
diff --git a/llvm/utils/TableGen/X86CompressEVEXTablesEmitter.cpp b/llvm/utils/TableGen/X86CompressEVEXTablesEmitter.cpp
index b03bcb6bc26b30..c519c07b243c24 100644
--- a/llvm/utils/TableGen/X86CompressEVEXTablesEmitter.cpp
+++ b/llvm/utils/TableGen/X86CompressEVEXTablesEmitter.cpp
@@ -167,12 +167,16 @@ void X86CompressEVEXTablesEmitter::run(raw_ostream &OS) {
   for (const CodeGenInstruction *Inst : PreCompressionInsts) {
     const Record *Rec = Inst->TheDef;
     uint8_t Opcode =
-        byteFromBitsInit(Inst->TheDef->getValueAsBitsInit("Opcode"));
+        byteFromBitsInit(Rec->getValueAsBitsInit("Opcode"));
+    StringRef Name = Rec->getName();
     const CodeGenInstruction *NewInst = nullptr;
-    if (ManualMap.find(Rec->getName()) != ManualMap.end()) {
+    if (ManualMap.find(Name) != ManualMap.end()) {
       Record *NewRec = Records.getDef(ManualMap.at(Rec->getName()));
       assert(NewRec && "Instruction not found!");
       NewInst = &Target.getInstruction(NewRec);
+    } else if (Name.ends_with("_EVEX")) {
+      if (auto *NewRec = Records.getDef(Name.drop_back(5)))
+        NewInst = &Target.getInstruction(NewRec);
     } else {
       // For each pre-compression instruction look for a match in the appropriate
       // vector (instructions with the same opcode) using function object

``````````

</details>


https://github.com/llvm/llvm-project/pull/77202