diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -5083,13 +5083,16 @@
   if (const ComplexType *CTy = Ty->getAs<ComplexType>())
     Ty = CTy->getElementType();
 
+  auto FloatUsesVector = [this](QualType Ty){
+    return Ty->isRealFloatingType() && &getContext().getFloatTypeSemantics(
+                                           Ty) == &llvm::APFloat::IEEEquad();
+  };
+
   // Only vector types of size 16 bytes need alignment (larger types are
   // passed via reference, smaller types are not aligned).
   if (Ty->isVectorType()) {
     return CharUnits::fromQuantity(getContext().getTypeSize(Ty) == 128 ? 16 : 8);
-  } else if (Ty->isRealFloatingType() &&
-             &getContext().getFloatTypeSemantics(Ty) ==
-                 &llvm::APFloat::IEEEquad()) {
+  } else if (FloatUsesVector(Ty)) {
     // According to ABI document section 'Optional Save Areas': If extended
     // precision floating-point values in IEEE BINARY 128 QUADRUPLE PRECISION
     // format are supported, map them to a single quadword, quadword aligned.
@@ -5116,7 +5119,9 @@
 
   // With special case aggregates, only vector base types need alignment.
   if (AlignAsType) {
-    return CharUnits::fromQuantity(AlignAsType->isVectorType() ? 16 : 8);
+    bool UsesVector = AlignAsType->isVectorType() ||
+                      FloatUsesVector(QualType(AlignAsType, 0));
+    return CharUnits::fromQuantity(UsesVector ? 16 : 8);
   }
 
   // Otherwise, we only need alignment for any aggregate type that
diff --git a/clang/test/CodeGen/ppc64le-varargs-f128.c b/clang/test/CodeGen/ppc64le-varargs-f128.c
--- a/clang/test/CodeGen/ppc64le-varargs-f128.c
+++ b/clang/test/CodeGen/ppc64le-varargs-f128.c
@@ -17,8 +17,11 @@
 
 #include <stdarg.h>
 
+typedef struct { long double x; } ldbl128_s;
+
 void foo_ld(long double);
 void foo_fq(__float128);
+void foo_ls(ldbl128_s);
 
 // Verify cases when OpenMP target's and host's long-double semantics differ.
 
@@ -99,3 +102,29 @@
   foo_ld(va_arg(ap, long double));
   va_end(ap);
 }
+
+// IEEE-LABEL: define{{.*}} void @long_double_struct
+// IEEE: %[[AP1:[0-9a-zA-Z_.]+]] = bitcast i8** %[[AP:[0-9a-zA-Z_.]+]] to i8*
+// IEEE: call void @llvm.va_start(i8* %[[AP1]])
+// IEEE: %[[CUR:[0-9a-zA-Z_.]+]] = load i8*, i8** %[[AP]]
+// IEEE: %[[P0:[0-9a-zA-Z_.]+]] = ptrtoint i8* %[[CUR]] to i64
+// IEEE: %[[P1:[0-9a-zA-Z_.]+]] = add i64 %[[P0]], 15
+// IEEE: %[[P2:[0-9a-zA-Z_.]+]] = and i64 %[[P1]], -16
+// IEEE: %[[ALIGN:[0-9a-zA-Z_.]+]] = inttoptr i64 %[[P2]] to i8*
+// IEEE: %[[V0:[0-9a-zA-Z_.]+]] = getelementptr inbounds i8, i8* %[[ALIGN]], i64 16
+// IEEE: store i8* %[[V0]], i8** %[[AP]], align 8
+// IEEE: %[[V1:[0-9a-zA-Z_.]+]] = bitcast i8* %[[ALIGN]] to %struct.ldbl128_s*
+// IEEE: %[[V2:[0-9a-zA-Z_.]+]] = bitcast %struct.ldbl128_s* %[[TMP:[0-9a-zA-Z_.]+]] to i8*
+// IEEE: %[[V3:[0-9a-zA-Z_.]+]] = bitcast %struct.ldbl128_s* %[[V1]] to i8*
+// IEEE: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 16 %[[V2]], i8* align 16 %[[V3]], i64 16, i1 false)
+// IEEE: %[[COERCE:[0-9a-zA-Z_.]+]] = getelementptr inbounds %struct.ldbl128_s, %struct.ldbl128_s* %[[TMP]], i32 0, i32 0
+// IEEE: %[[V4:[0-9a-zA-Z_.]+]] = load fp128, fp128* %[[COERCE]], align 16
+// IEEE: call void @foo_ls(fp128 inreg %[[V4]])
+// IEEE: %[[AP2:[0-9a-zA-Z_.]+]] = bitcast i8** %[[AP]] to i8*
+// IEEE: call void @llvm.va_end(i8* %[[AP2]])
+void long_double_struct(int n, ...) {
+  va_list ap;
+  va_start(ap, n);
+  foo_ls(va_arg(ap, ldbl128_s));
+  va_end(ap);
+}