diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
--- a/clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -11968,16 +11968,16 @@
                                               llvm::Function *Fn) {
   ASTContext &C = CGM.getContext();
   FD = FD->getMostRecentDecl();
-  // Map params to their positions in function decl.
-  llvm::DenseMap<const Decl *, unsigned> ParamPositions;
-  if (isa<CXXMethodDecl>(FD))
-    ParamPositions.try_emplace(FD, 0);
-  unsigned ParamPos = ParamPositions.size();
-  for (const ParmVarDecl *P : FD->parameters()) {
-    ParamPositions.try_emplace(P->getCanonicalDecl(), ParamPos);
-    ++ParamPos;
-  }
   while (FD) {
+    // Map params to their positions in function decl.
+    llvm::DenseMap<const Decl *, unsigned> ParamPositions;
+    if (isa<CXXMethodDecl>(FD))
+      ParamPositions.try_emplace(FD, 0);
+    unsigned ParamPos = ParamPositions.size();
+    for (const ParmVarDecl *P : FD->parameters()) {
+      ParamPositions.try_emplace(P->getCanonicalDecl(), ParamPos);
+      ++ParamPos;
+    }
     for (const auto *Attr : FD->specific_attrs<OMPDeclareSimdDeclAttr>()) {
       llvm::SmallVector<ParamAttrTy, 8> ParamAttrs(ParamPositions.size());
       // Mark uniform parameters.
@@ -11989,6 +11989,7 @@
         } else {
           const auto *PVD = cast<ParmVarDecl>(cast<DeclRefExpr>(E)->getDecl())
                                 ->getCanonicalDecl();
+          assert(ParamPositions.find(PVD) != ParamPositions.end());
           Pos = ParamPositions[PVD];
         }
         ParamAttrs[Pos].Kind = Uniform;
@@ -12005,6 +12006,7 @@
         } else {
           const auto *PVD = cast<ParmVarDecl>(cast<DeclRefExpr>(E)->getDecl())
                                 ->getCanonicalDecl();
+          assert(ParamPositions.find(PVD) != ParamPositions.end());
           Pos = ParamPositions[PVD];
           ParmTy = PVD->getType();
         }
@@ -12030,6 +12032,7 @@
         } else {
           const auto *PVD = cast<ParmVarDecl>(cast<DeclRefExpr>(E)->getDecl())
                                 ->getCanonicalDecl();
+          assert(ParamPositions.find(PVD) != ParamPositions.end());
           Pos = ParamPositions[PVD];
           if (auto *P = dyn_cast<PointerType>(PVD->getType()))
             PtrRescalingFactor = CGM.getContext()
@@ -12048,6 +12051,8 @@
               if (const auto *StridePVD =
                       dyn_cast<ParmVarDecl>(DRE->getDecl())) {
                 ParamAttr.Kind = LinearWithVarStride;
+                assert(ParamPositions.find(StridePVD->getCanonicalDecl()) !=
+                       ParamPositions.end());
                 ParamAttr.StrideOrArg = llvm::APSInt::getUnsigned(
                     ParamPositions[StridePVD->getCanonicalDecl()]);
               }
diff --git a/clang/test/OpenMP/declare_simd_codegen.cpp b/clang/test/OpenMP/declare_simd_codegen.cpp
--- a/clang/test/OpenMP/declare_simd_codegen.cpp
+++ b/clang/test/OpenMP/declare_simd_codegen.cpp
@@ -153,6 +153,23 @@
 // CHECK-DAG: "_ZGVdN4v__Z5add_1Pf"
 // CHECK-DAG: "_ZGVeN8v__Z5add_1Pf"
 
+// CHECK-NOT: _ZGVbN2vv__Z5add_1Pf
+// CHECK-NOT: _ZGVcN4vv__Z5add_1Pf
+// CHECK-NOT: _ZGVdN4vv__Z5add_1Pf
+// CHECK-NOT: _ZGVeN8vv__Z5add_1Pf
+// CHECK-NOT: _ZGVbM32vv__Z5add_1Pf
+// CHECK-NOT: _ZGVcM32vv__Z5add_1Pf
+// CHECK-NOT: _ZGVdM32vv__Z5add_1Pf
+// CHECK-NOT: _ZGVeM32vv__Z5add_1Pf
+// CHECK-NOT: _ZGVbN4l32v__Z5add_1Pf
+// CHECK-NOT: _ZGVcN8l32v__Z5add_1Pf
+// CHECK-NOT: _ZGVdN8l32v__Z5add_1Pf
+// CHECK-NOT: _ZGVeN16l32v__Z5add_1Pf
+// CHECK-NOT: _ZGVbM4l32v__Z5add_1Pf
+// CHECK-NOT: _ZGVcM8l32v__Z5add_1Pf
+// CHECK-NOT: _ZGVdM8l32v__Z5add_1Pf
+// CHECK-NOT: _ZGVeM16l32v__Z5add_1Pf
+
 // CHECK-DAG: "_ZGVbM2va16va16vv__Z1hIiEvPT_S1_S1_S1_"
 // CHECK-DAG: "_ZGVbN2va16va16vv__Z1hIiEvPT_S1_S1_S1_"
 // CHECK-DAG: "_ZGVcM4va16va16vv__Z1hIiEvPT_S1_S1_S1_"