diff --git a/clang/lib/Basic/Targets/AArch64.h b/clang/lib/Basic/Targets/AArch64.h
--- a/clang/lib/Basic/Targets/AArch64.h
+++ b/clang/lib/Basic/Targets/AArch64.h
@@ -96,7 +96,7 @@
       Constraint += 2;
       break;
     default:
-      R = std::string(1, *Constraint);
+      R = TargetInfo::convertConstraint(Constraint);
       break;
     }
     return R;
diff --git a/clang/test/CodeGen/inline-asm-p-constraint.c b/clang/test/CodeGen/inline-asm-p-constraint.c
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGen/inline-asm-p-constraint.c
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple aarch64-linux-gnu | FileCheck %s
+void foo(void* ptr) {
+  asm volatile("prfm pldl1keep, %a0\n" : : "p" (ptr));
+  // CHECK:     call void asm sideeffect "prfm pldl1keep, ${0:a}\0A", "r"(i8* %0)
+  // CHECK-NOT: call void asm sideeffect "prfm pldl1keep, ${0:a}\0A", "p"(i8* %0)
+}