[llvm] [utils/TableGen/X86CompressEVEXTablesEmitter.cpp] Make sure the tablegen output for the `checkPredicate` function is deterministic (PR #84533)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-x86

Author: Argyrios Kyrtzidis (akyrtzi)

<details>
<summary>Changes</summary>

The output for the `checkPredicate` function was depending on a `std::map` iteration that was not deterministic from run to run, so the contents of `X86GenCompressEVEXTables.inc` were not deterministic.

Make a change to sort the entries before iterating over them.

---
Full diff: https://github.com/llvm/llvm-project/pull/84533.diff


1 Files Affected:

- (modified) llvm/utils/TableGen/X86CompressEVEXTablesEmitter.cpp (+15-3) 


``````````diff
diff --git a/llvm/utils/TableGen/X86CompressEVEXTablesEmitter.cpp b/llvm/utils/TableGen/X86CompressEVEXTablesEmitter.cpp
index b96d16b9797cf3..326a9dfbcfefaa 100644
--- a/llvm/utils/TableGen/X86CompressEVEXTablesEmitter.cpp
+++ b/llvm/utils/TableGen/X86CompressEVEXTablesEmitter.cpp
@@ -82,15 +82,27 @@ void X86CompressEVEXTablesEmitter::printTable(const std::vector<Entry> &Table,
 
 void X86CompressEVEXTablesEmitter::printCheckPredicate(
     const PredicateInstMap &PredicateInsts, raw_ostream &OS) {
+  // Create a sorted list of the map entries so that the tablegen output is
+  // deterministic.
+  typedef std::pair<StringRef, const std::vector<const CodeGenInstruction *> *>
+      PredicateInstsTy;
+  std::vector<PredicateInstsTy> SortedPredicateInsts;
+  for (const auto &[Key, Val] : PredicateInsts) {
+    SortedPredicateInsts.push_back({Key->getValueAsString("CondString"), &Val});
+  }
+  llvm::sort(SortedPredicateInsts,
+             [](const PredicateInstsTy &LHS, const PredicateInstsTy &RHS) {
+               return LHS.first < RHS.first;
+             });
 
   OS << "static bool checkPredicate(unsigned Opc, const X86Subtarget "
         "*Subtarget) {\n"
      << "  switch (Opc) {\n"
      << "  default: return true;\n";
-  for (const auto &[Key, Val] : PredicateInsts) {
-    for (const auto &Inst : Val)
+  for (const auto &[Key, Val] : SortedPredicateInsts) {
+    for (const auto &Inst : *Val)
       OS << "  case X86::" << Inst->TheDef->getName() << ":\n";
-    OS << "    return " << Key->getValueAsString("CondString") << ";\n";
+    OS << "    return " << Key << ";\n";
   }
 
   OS << "  }\n";

``````````

</details>


https://github.com/llvm/llvm-project/pull/84533