diff --git a/clang/test/Index/auto-function-param.cpp b/clang/test/Index/auto-function-param.cpp
new file mode 100644
index 0000000000000..bb32b72e6f7a2
--- /dev/null
+++ b/clang/test/Index/auto-function-param.cpp
@@ -0,0 +1,24 @@
+// Test case for auto function parameter reported as CXType_Auto
+// This test verifies that auto parameters in function declarations
+// are properly reported as CXType_Auto in the libclang C API
+// See issue #172072
+
+// RUN: c-index-test -test-type %s | FileCheck %s
+
+// Function with auto parameter
+int bar(auto p) {
+  return p;
+}
+
+// CHECK: FunctionDecl=bar:{{.*}} CXType_FunctionProto
+// CHECK: ParmDecl=p:{{.*}} CXType_Auto
+// C++20 constrained auto parameter
+template<typename T>
+concept Integral = __is_integral(T);
+
+int baz(Integral auto q) {
+  return q;
+}
+
+// CHECK: FunctionDecl=baz:{{.*}} CXType_FunctionProto
+// CHECK: ParmDecl=q:{{.*}} CXType_Auto
\ No newline at end of file
diff --git a/clang/tools/libclang/CIndex.cpp b/clang/tools/libclang/CIndex.cpp
index 32e84248c1b27..bb0816b0447a9 100644
--- a/clang/tools/libclang/CIndex.cpp
+++ b/clang/tools/libclang/CIndex.cpp
@@ -1789,6 +1789,15 @@ bool CursorVisitor::VisitAdjustedTypeLoc(AdjustedTypeLoc TL) {
   return Visit(TL.getOriginalLoc());
 }
 
+bool CursorVisitor::VisitAutoTypeLoc(AutoTypeLoc TL) {
+  // AutoTypeLoc represents the location of an auto type specifier.
+  // We do not visit children because the auto type itself is complete.
+  // This handler ensures that auto function parameters are properly
+  // reported as CXType_Auto in the libclang C API, rather than being
+  // incorrectly reported as TypeRef/unexposed.
+  return false;
+}
+
 bool CursorVisitor::VisitDeducedTemplateSpecializationTypeLoc(
     DeducedTemplateSpecializationTypeLoc TL) {
   if (VisitTemplateName(TL.getTypePtr()->getTemplateName(),
diff --git a/clang/tools/libclang/CXType.cpp b/clang/tools/libclang/CXType.cpp
index 3feb56334d79c..9115108efd24d 100644
--- a/clang/tools/libclang/CXType.cpp
+++ b/clang/tools/libclang/CXType.cpp
@@ -150,6 +150,14 @@ CXType cxtype::MakeCXType(QualType T, CXTranslationUnit TU) {
       return MakeCXType(PTT->getInnerType(), TU);
     }
 
+    // Handle auto in function parameters (including constrained auto)
+    if (auto *TTP = T->getAs<TemplateTypeParmType>()) {
+      auto *D = TTP->getDecl();
+      if (D && D->isImplicit()) {
+        TK = CXType_Auto;
+      }
+    }
+
     ASTContext &Ctx = cxtu::getASTUnit(TU)->getASTContext();
     if (Ctx.getLangOpts().ObjC) {
       QualType UnqualT = T.getUnqualifiedType();
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 9ba1c06b6d3fa..757f7952a2ca0 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -2912,6 +2912,7 @@ uint64_t LoopVectorizationCostModel::getPredBlockCostDivisor(
   uint64_t BBFreq = getBFI().getBlockFreq(BB).getFrequency();
   assert(HeaderFreq >= BBFreq &&
          "Header has smaller block freq than dominated BB?");
+  assert(BBFreq != 0 && "BlockFrequencyInfo should never return zero frequency");
   return std::round((double)HeaderFreq / BBFreq);
 }