Revert "[OpenMP][SIMD][FIX] Use conservative "omp simd ordered" lowering" (llvm#126079)

Reverts llvm#123867 to fix the test failures
https://lab.llvm.org/buildbot/#/builders/144/builds/17521

Author: alexey-bataev

clang/lib/CodeGen/CGStmtOpenMP.cpp

@@ -2457,86 +2457,10 @@ static void emitSimdlenSafelenClause(CodeGenFunction &CGF,
   }
 }
 
-// Check for the presence of an `OMPOrderedDirective`,
-// i.e., `ordered` in `#pragma omp ordered simd`.
-//
-// Consider the following source code:
-// ```
-// __attribute__((noinline)) void omp_simd_loop(float X[ARRAY_SIZE][ARRAY_SIZE])
-// {
-//     for (int r = 1; r < ARRAY_SIZE; ++r) {
-//         for (int c = 1; c < ARRAY_SIZE; ++c) {
-// #pragma omp simd
-//             for (int k = 2; k < ARRAY_SIZE; ++k) {
-// #pragma omp ordered simd
-//                 X[r][k] = X[r][k - 2] + sinf((float)(r / c));
-//             }
-//         }
-//     }
-// }
-// ```
-//
-// Suppose we are in `CodeGenFunction::EmitOMPSimdInit(const OMPLoopDirective
-// &D)`. By examining `D.dump()` we have the following AST containing
-// `OMPOrderedDirective`:
-//
-// ```
-// OMPSimdDirective 0x1c32950
-// `-CapturedStmt 0x1c32028
-//   |-CapturedDecl 0x1c310e8
-//   | |-ForStmt 0x1c31e30
-//   | | |-DeclStmt 0x1c31298
-//   | | | `-VarDecl 0x1c31208  used k 'int' cinit
-//   | | |   `-IntegerLiteral 0x1c31278 'int' 2
-//   | | |-<<<NULL>>>
-//   | | |-BinaryOperator 0x1c31308 'int' '<'
-//   | | | |-ImplicitCastExpr 0x1c312f0 'int' <LValueToRValue>
-//   | | | | `-DeclRefExpr 0x1c312b0 'int' lvalue Var 0x1c31208 'k' 'int'
-//   | | | `-IntegerLiteral 0x1c312d0 'int' 256
-//   | | |-UnaryOperator 0x1c31348 'int' prefix '++'
-//   | | | `-DeclRefExpr 0x1c31328 'int' lvalue Var 0x1c31208 'k' 'int'
-//   | | `-CompoundStmt 0x1c31e18
-//   | |   `-OMPOrderedDirective 0x1c31dd8
-//   | |     |-OMPSimdClause 0x1c31380
-//   | |     `-CapturedStmt 0x1c31cd0
-// ```
-//
-// Note the presence of `OMPOrderedDirective` above:
-// It's (transitively) nested in a `CapturedStmt` representing the pragma
-// annotated compound statement. Thus, we need to consider this nesting and
-// include checking the `getCapturedStmt` in this case.
-static bool hasOrderedDirective(const Stmt *S) {
-  if (isa<OMPOrderedDirective>(S))
-    return true;
-
-  if (const auto *CS = dyn_cast<CapturedStmt>(S))
-    return hasOrderedDirective(CS->getCapturedStmt());
-
-  for (const Stmt *Child : S->children()) {
-    if (Child && hasOrderedDirective(Child))
-      return true;
-  }
-
-  return false;
-}
-
-static void applyConservativeSimdOrderedDirective(const Stmt &AssociatedStmt,
-                                                  LoopInfoStack &LoopStack) {
-  // Check for the presence of an `OMPOrderedDirective`
-  // i.e., `ordered` in `#pragma omp ordered simd`
-  bool HasOrderedDirective = hasOrderedDirective(&AssociatedStmt);
-  // If present then conservatively disable loop vectorization
-  // analogously to how `emitSimdlenSafelenClause` does.
-  if (HasOrderedDirective)
-    LoopStack.setParallel(/*Enable=*/false);
-}
-
 void CodeGenFunction::EmitOMPSimdInit(const OMPLoopDirective &D) {
   // Walk clauses and process safelen/lastprivate.
   LoopStack.setParallel(/*Enable=*/true);
   LoopStack.setVectorizeEnable();
-  const Stmt *AssociatedStmt = D.getAssociatedStmt();
-  applyConservativeSimdOrderedDirective(*AssociatedStmt, LoopStack);
   emitSimdlenSafelenClause(*this, D);
   if (const auto *C = D.getSingleClause<OMPOrderClause>())
     if (C->getKind() == OMPC_ORDER_concurrent)