diff --git a/clang/lib/Basic/Targets/RISCV.h b/clang/lib/Basic/Targets/RISCV.h
--- a/clang/lib/Basic/Targets/RISCV.h
+++ b/clang/lib/Basic/Targets/RISCV.h
@@ -31,6 +31,7 @@
   bool HasD = false;
   bool HasC = false;
   bool HasB = false;
+  bool HasP = false;
   bool HasV = false;
   bool HasZba = false;
   bool HasZbb = false;
diff --git a/clang/lib/Basic/Targets/RISCV.cpp b/clang/lib/Basic/Targets/RISCV.cpp
--- a/clang/lib/Basic/Targets/RISCV.cpp
+++ b/clang/lib/Basic/Targets/RISCV.cpp
@@ -149,6 +149,9 @@
     Builder.defineMacro("__riscv_bitmanip");
   }
 
+  if (HasP)
+    Builder.defineMacro("__riscv_p", "90000");
+
   if (HasV) {
     Builder.defineMacro("__riscv_v", "1000000");
     Builder.defineMacro("__riscv_vector");
@@ -210,6 +213,7 @@
       .Case("d", HasD)
       .Case("c", HasC)
       .Case("experimental-b", HasB)
+      .Case("experimental-p", HasP)
       .Case("experimental-v", HasV)
       .Case("experimental-zba", HasZba)
       .Case("experimental-zbb", HasZbb)
@@ -244,6 +248,8 @@
       HasC = true;
     else if (Feature == "+experimental-b")
       HasB = true;
+    else if (Feature == "+experimental-p")
+      HasP = true;
     else if (Feature == "+experimental-v")
       HasV = true;
     else if (Feature == "+experimental-zba")
diff --git a/clang/test/Preprocessor/riscv-target-features.c b/clang/test/Preprocessor/riscv-target-features.c
--- a/clang/test/Preprocessor/riscv-target-features.c
+++ b/clang/test/Preprocessor/riscv-target-features.c
@@ -109,6 +109,12 @@
 // CHECK-DOUBLE-NOT: __riscv_float_abi_soft
 // CHECK-DOUBLE-NOT: __riscv_float_abi_single
 
+// RUN: %clang -target riscv32-unknown-linux-gnu -menable-experimental-extensions -march=rv32ip0p9 -x c -E -dM %s \
+// RUN: -o - | FileCheck --check-prefix=CHECK-P-EXT %s
+// RUN: %clang -target riscv64-unknown-linux-gnu -menable-experimental-extensions -march=rv64ip0p9 -x c -E -dM %s \
+// RUN: -o - | FileCheck --check-prefix=CHECK-P-EXT %s
+// CHECK-P-EXT: __riscv_p 90000
+
 // RUN: %clang -target riscv32-unknown-linux-gnu -menable-experimental-extensions \
 // RUN:   -march=rv32iv1p0 -x c -E -dM %s \
 // RUN:   -o - | FileCheck --check-prefix=CHECK-V-EXT %s