diff --git a/llvm/docs/RISCVUsage.rst b/llvm/docs/RISCVUsage.rst
--- a/llvm/docs/RISCVUsage.rst
+++ b/llvm/docs/RISCVUsage.rst
@@ -109,9 +109,11 @@
      ``Zicbom``       Assembly Support
      ``Zicbop``       Assembly Support
      ``Zicboz``       Assembly Support
+     ``Zicntr``       (`See Note <#riscv-i2p1-note>`__)
      ``Zicsr``        (`See Note <#riscv-i2p1-note>`__)
      ``Zifencei``     (`See Note <#riscv-i2p1-note>`__)
      ``Zihintpause``  Assembly Support
+     ``Zihpm``        (`See Note <#riscv-i2p1-note>`__)
      ``Zkn``          Supported
      ``Zknd``         Supported (`See note <#riscv-scalar-crypto-note2>`__)
      ``Zkne``         Supported (`See note <#riscv-scalar-crypto-note2>`__)
@@ -165,8 +167,8 @@
 
 .. _riscv-i2p1-note:
 
-``zicsr``, ``zifencei``
-  Between versions 2.0 and 2.1 of the base I specification, a backwards incompatible change was made to remove selected instructions and CSRs from the base ISA.  These instructions were grouped into a set of new extensions, but were no longer required by the base ISA.  This change is described in "Preface to Document Version 20190608-Base-Ratified" from the specification document.  LLVM currently implements version 2.1 of the base specification. To maintain compatibility, instructions from these extensions are accepted without being in the ``-march`` string.  LLVM also allows the explicit specification of the extensions in an ``-march`` string.
+``zicntr``, ``zicsr``, ``zifencei``, ``zihpm``
+  Between versions 2.0 and 2.1 of the base I specification, a backwards incompatible change was made to remove selected instructions and CSRs from the base ISA.  These instructions were grouped into a set of new extensions, but were no longer required by the base ISA.  This change is partially described in "Preface to Document Version 20190608-Base-Ratified" from the specification document (the ``zicntr`` and ``zihpm`` bits are not mentioned).  LLVM currently implements version 2.1 of the base specification. To maintain compatibility, instructions from these extensions are accepted without being in the ``-march`` string.  LLVM also allows the explicit specification of the extensions in an ``-march`` string.
 
 Experimental Extensions
 =======================
diff --git a/llvm/lib/Support/RISCVISAInfo.cpp b/llvm/lib/Support/RISCVISAInfo.cpp
--- a/llvm/lib/Support/RISCVISAInfo.cpp
+++ b/llvm/lib/Support/RISCVISAInfo.cpp
@@ -107,8 +107,10 @@
     {"zicbom", RISCVExtensionVersion{1, 0}},
     {"zicboz", RISCVExtensionVersion{1, 0}},
     {"zicbop", RISCVExtensionVersion{1, 0}},
+    {"zicntr", RISCVExtensionVersion{1, 0}},
     {"zicsr", RISCVExtensionVersion{2, 0}},
     {"zifencei", RISCVExtensionVersion{2, 0}},
+    {"zihpm", RISCVExtensionVersion{1, 0}},
 
     {"zawrs", RISCVExtensionVersion{1, 0}},
 
diff --git a/llvm/lib/Target/RISCV/RISCVFeatures.td b/llvm/lib/Target/RISCV/RISCVFeatures.td
--- a/llvm/lib/Target/RISCV/RISCVFeatures.td
+++ b/llvm/lib/Target/RISCV/RISCVFeatures.td
@@ -86,6 +86,14 @@
                                    AssemblerPredicate<(all_of FeatureStdExtZifencei),
                                    "'Zifencei' (fence.i)">;
 
+def FeatureStdExtZicntr
+    : SubtargetFeature<"zicntr", "HasStdExtZicntr", "true",
+                       "'zicntr' (Base Counters and Timers)">;
+
+def FeatureStdExtZihpm
+    : SubtargetFeature<"zihpm", "HasStdExtZihpm", "true",
+                       "'zihpm' (Hardware Performance Counters)">;
+
 def FeatureStdExtZfhmin
     : SubtargetFeature<"zfhmin", "HasStdExtZfhmin", "true",
                        "'Zfhmin' (Half-Precision Floating-Point Minimal)",
diff --git a/llvm/test/CodeGen/RISCV/attributes.ll b/llvm/test/CodeGen/RISCV/attributes.ll
--- a/llvm/test/CodeGen/RISCV/attributes.ll
+++ b/llvm/test/CodeGen/RISCV/attributes.ll
@@ -54,6 +54,8 @@
 ; RUN: llc -mtriple=riscv32 -mattr=+experimental-zcf %s -o - | FileCheck --check-prefixes=CHECK,RV32ZCF %s
 ; RUN: llc -mtriple=riscv32 -mattr=+zicsr %s -o - | FileCheck --check-prefixes=CHECK,RV32ZICSR %s
 ; RUN: llc -mtriple=riscv32 -mattr=+zifencei %s -o - | FileCheck --check-prefixes=CHECK,RV32ZIFENCEI %s
+; RUN: llc -mtriple=riscv32 -mattr=+zicntr %s -o - | FileCheck --check-prefixes=CHECK,RV32ZICNTR %s
+; RUN: llc -mtriple=riscv32 -mattr=+zihpm %s -o - | FileCheck --check-prefixes=CHECK,RV32ZIHPM %s
 ; RUN: llc -mtriple=riscv32 -mattr=+experimental-zfa %s -o - | FileCheck --check-prefixes=CHECK,RV32ZFA %s
 ; RUN: llc -mtriple=riscv32 -mattr=+zve32x -mattr=+experimental-zvbb %s -o - | FileCheck --check-prefix=RV32ZVBB %s
 ; RUN: llc -mtriple=riscv32 -mattr=+zve64x -mattr=+experimental-zvbc %s -o - | FileCheck --check-prefix=RV32ZVBC %s
@@ -130,6 +132,8 @@
 ; RUN: llc -mtriple=riscv64 -mattr=+experimental-zcd %s -o - | FileCheck --check-prefixes=CHECK,RV64ZCD %s
 ; RUN: llc -mtriple=riscv64 -mattr=+zicsr %s -o - | FileCheck --check-prefixes=CHECK,RV64ZICSR %s
 ; RUN: llc -mtriple=riscv64 -mattr=+zifencei %s -o - | FileCheck --check-prefixes=CHECK,RV64ZIFENCEI %s
+; RUN: llc -mtriple=riscv64 -mattr=+zicntr %s -o - | FileCheck --check-prefixes=CHECK,RV64ZICNTR %s
+; RUN: llc -mtriple=riscv64 -mattr=+zihpm %s -o - | FileCheck --check-prefixes=CHECK,RV64ZIHPM %s
 ; RUN: llc -mtriple=riscv64 -mattr=+experimental-zfa %s -o - | FileCheck --check-prefixes=CHECK,RV64ZFA %s
 ; RUN: llc -mtriple=riscv64 -mattr=+zve32x -mattr=+experimental-zvbb %s -o - | FileCheck --check-prefix=RV64ZVBB %s
 ; RUN: llc -mtriple=riscv64 -mattr=+zve64x -mattr=+experimental-zvbc %s -o - | FileCheck --check-prefix=RV64ZVBC %s
@@ -201,6 +205,8 @@
 ; RV32ZCF: .attribute 5, "rv32i2p1_zcf1p0"
 ; RV32ZICSR: .attribute 5, "rv32i2p1_zicsr2p0"
 ; RV32ZIFENCEI: .attribute 5, "rv32i2p1_zifencei2p0"
+; RV32ZICNTR: .attribute 5, "rv32i2p1_zicntr1p0"
+; RV32ZIHPM: .attribute 5, "rv32i2p1_zihpm1p0"
 ; RV32ZFA: .attribute 5, "rv32i2p1_f2p2_zicsr2p0_zfa0p2"
 ; RV32ZVBB: .attribute 5, "rv32i2p1_zicsr2p0_zvbb0p5_zve32x1p0_zvl32b1p0"
 ; RV32ZVBC: .attribute 5, "rv32i2p1_zicsr2p0_zvbc0p5_zve32x1p0_zve64x1p0_zvl32b1p0_zvl64b1p0"
@@ -276,6 +282,8 @@
 ; RV64ZCD: .attribute 5, "rv64i2p1_zcd1p0"
 ; RV64ZICSR: .attribute 5, "rv64i2p1_zicsr2p0"
 ; RV64ZIFENCEI: .attribute 5, "rv64i2p1_zifencei2p0"
+; RV64ZICNTR: .attribute 5, "rv64i2p1_zicntr1p0"
+; RV64ZIHPM: .attribute 5, "rv64i2p1_zihpm1p0"
 ; RV64ZFA: .attribute 5, "rv64i2p1_f2p2_zicsr2p0_zfa0p2"
 ; RV64ZVBB: .attribute 5, "rv64i2p1_zicsr2p0_zvbb0p5_zve32x1p0_zvl32b1p0"
 ; RV64ZVBC: .attribute 5, "rv64i2p1_zicsr2p0_zvbc0p5_zve32x1p0_zve64x1p0_zvl32b1p0_zvl64b1p0"