[TableGen] Use MapVector to remove non-determinism

This fixes found non-determinism when `LLVM_REVERSE_ITERATION`
option is `ON`.

Fixes #79420.

Reviewers: ilovepi, MaskRay

Reviewed By: MaskRay

Pull Request: #79411

(cherry picked from commit 41fe98a)

Author: wangpc-pp

llvm/test/TableGen/address-space-patfrags.td

@@ -46,7 +46,7 @@ def inst_d : Instruction {
   let InOperandList = (ins GPR32:$src0, GPR32:$src1);
 }
 
-// SDAG: case 1: {
+// SDAG: case 0: {
 // SDAG-NEXT: // Predicate_pat_frag_b
 // SDAG-NEXT: // Predicate_truncstorei16_addrspace
 // SDAG-NEXT: SDNode *N = Node;
@@ -69,7 +69,7 @@ def : Pat <
 >;
 
 
-// SDAG: case 6: {
+// SDAG: case 4: {
 // SDAG: // Predicate_pat_frag_a
 // SDAG-NEXT: SDNode *N = Node;
 // SDAG-NEXT: (void)N;

llvm/utils/TableGen/DAGISelMatcherEmitter.cpp

@@ -57,7 +57,8 @@ class MatcherTableEmitter {
 
   // We de-duplicate the predicates by code string, and use this map to track
   // all the patterns with "identical" predicates.
-  StringMap<TinyPtrVector<TreePattern *>> NodePredicatesByCodeToRun;
+  MapVector<std::string, TinyPtrVector<TreePattern *>, StringMap<unsigned>>
+      NodePredicatesByCodeToRun;
 
   std::vector<std::string> PatternPredicates;