[RISCV] Add support for RISC-V Pointer Masking (#79929)

This patch implements the v0.8.1 specification. This patch reports
version 0.8 in llvm since `RISCVISAInfo::ExtensionVersion` only has a
`Major` and `Minor` version number. This patch includes includes support
of the `Ssnpm`, `Smnpm`, `Smmpm`, `Sspm` and `Supm` extensions that make
up RISC-V pointer masking.

All of these extensions require emitting attribute containing correct
`march` string.

`Ssnpm`, `Smnpm`, `Smmpm` extensions introduce a 2-bit WARL field (PMM).
The extension does not specify how PMM is set, and therefore this patch
does not need to address this. One example of how it *could* be set is
using the Zicsr instructions to update the PMM bits of the described
registers.

The full specification can be found at
https://github.com/riscv/riscv-j-extension/blob/master/zjpm-spec.pdf

clang/test/Preprocessor/riscv-target-features.c

@@ -159,6 +159,11 @@
 
 // Experimental extensions
 
+// CHECK-NOT: __riscv_smmpm{{.*$}}
+// CHECK-NOT: __riscv_smnpm{{.*$}}
+// CHECK-NOT: __riscv_ssnpm{{.*$}}
+// CHECK-NOT: __riscv_sspm{{.*$}}
+// CHECK-NOT: __riscv_supm{{.*$}}
 // CHECK-NOT: __riscv_zaamo {{.*$}}
 // CHECK-NOT: __riscv_zacas {{.*$}}
 // CHECK-NOT: __riscv_zalasr {{.*$}}
@@ -1567,6 +1572,46 @@
 // RUN:   -o - | FileCheck --check-prefix=CHECK-ZICFISS-EXT %s
 // CHECK-ZICFISS-EXT: __riscv_zicfiss 4000{{$}}
 
+// RUN: %clang --target=riscv32 -menable-experimental-extensions \
+// RUN:   -march=rv32i_ssnpm0p8 -E -dM %s \
+// RUN:   -o - | FileCheck --check-prefix=CHECK-SSNPM-EXT %s
+// RUN: %clang --target=riscv64 -menable-experimental-extensions \
+// RUN:   -march=rv64i_ssnpm0p8 -E -dM %s \
+// RUN:   -o - | FileCheck --check-prefix=CHECK-SSNPM-EXT %s
+// CHECK-SSNPM-EXT: __riscv_ssnpm 8000{{$}}
+
+// RUN: %clang --target=riscv32 -menable-experimental-extensions \
+// RUN:   -march=rv32i_smnpm0p8 -E -dM %s \
+// RUN:   -o - | FileCheck --check-prefix=CHECK-SMNPM-EXT %s
+// RUN: %clang --target=riscv64 -menable-experimental-extensions \
+// RUN:   -march=rv64i_smnpm0p8 -E -dM %s \
+// RUN:   -o - | FileCheck --check-prefix=CHECK-SMNPM-EXT %s
+// CHECK-SMNPM-EXT: __riscv_smnpm 8000{{$}}
+
+// RUN: %clang --target=riscv32 -menable-experimental-extensions \
+// RUN:   -march=rv32i_smmpm0p8 -E -dM %s \
+// RUN:   -o - | FileCheck --check-prefix=CHECK-SMMPM-EXT %s
+// RUN: %clang --target=riscv64 -menable-experimental-extensions \
+// RUN:   -march=rv64i_smmpm0p8 -E -dM %s \
+// RUN:   -o - | FileCheck --check-prefix=CHECK-SMMPM-EXT %s
+// CHECK-SMMPM-EXT: __riscv_smmpm 8000{{$}}
+
+// RUN: %clang --target=riscv32 -menable-experimental-extensions \
+// RUN:   -march=rv32i_sspm0p8 -E -dM %s \
+// RUN:   -o - | FileCheck --check-prefix=CHECK-SSPM-EXT %s
+// RUN: %clang --target=riscv64 \
+// RUN:   -march=rv64i_sspm0p8 -E -dM %s -menable-experimental-extensions \
+// RUN:   -o - | FileCheck --check-prefix=CHECK-SSPM-EXT %s
+// CHECK-SSPM-EXT: __riscv_sspm 8000{{$}}
+
+// RUN: %clang --target=riscv32 -menable-experimental-extensions \
+// RUN:   -march=rv32i_supm0p8 -E -dM %s \
+// RUN:   -o - | FileCheck --check-prefix=CHECK-SUPM-EXT %s
+// RUN: %clang --target=riscv64 \
+// RUN:   -march=rv64i_supm0p8 -E -dM %s -menable-experimental-extensions \
+// RUN:   -o - | FileCheck --check-prefix=CHECK-SUPM-EXT %s
+// CHECK-SUPM-EXT: __riscv_supm 8000{{$}}
+
 // Misaligned
 
 // RUN: %clang --target=riscv32-unknown-linux-gnu -march=rv32i -E -dM %s \

llvm/docs/RISCVUsage.rst

@@ -243,6 +243,9 @@ LLVM supports (to various degrees) a number of experimental extensions.  All exp
 
 The primary goal of experimental support is to assist in the process of ratification by providing an existence proof of an implementation, and simplifying efforts to validate the value of a proposed extension against large code bases.  Experimental extensions are expected to either transition to ratified status, or be eventually removed.  The decision on whether to accept an experimental extension is currently done on an entirely case by case basis; if you want to propose one, attending the bi-weekly RISC-V sync-up call is strongly advised.
 
+``experimental-ssnpm``, ``experimental-smnpm``, ``experimental-smmpm``, ``experimental-sspm``, ``experimental-supm``
+  LLVM implements the `v0.8.1 draft specification <https://github.com/riscv/riscv-j-extension/blob/master/zjpm-spec.pdf>`
+
 ``experimental-zabha``
   LLVM implements assembler support for the `v1.0-rc1 draft specification <https://github.com/riscv/riscv-zabha/tree/v1.0-rc1>`_.
 

llvm/docs/ReleaseNotes.rst

@@ -101,6 +101,7 @@ Changes to the RISC-V Backend
 * The names of the majority of the S-prefixed (supervisor-level) extension
   names in the RISC-V profiles specification are now recognised.
 * Codegen support was added for the Zimop (May-Be-Operations) extension.
+* The experimental Ssnpm, Smnpm, Smmpm, Sspm, and Supm 0.8.1 Pointer Masking extensions are supported.
 
 Changes to the WebAssembly Backend
 ----------------------------------

llvm/lib/Support/RISCVISAInfo.cpp

@@ -211,6 +211,12 @@ static const RISCVSupportedExtension SupportedExtensions[] = {
 // NOTE: This table should be sorted alphabetically by extension name.
 // clang-format off
 static const RISCVSupportedExtension SupportedExperimentalExtensions[] = {
+    {"smmpm", {0, 8}},
+    {"smnpm", {0, 8}},
+    {"ssnpm", {0, 8}},
+    {"sspm", {0, 8}},
+    {"supm", {0, 8}},
+
     {"zaamo", {0, 2}},
     {"zabha", {1, 0}},
     {"zacas", {1, 0}},

llvm/lib/Target/RISCV/RISCVFeatures.td

@@ -876,6 +876,40 @@ def FeatureStdExtSvpbmt
     : SubtargetFeature<"svpbmt", "HasStdExtSvpbmt", "true",
                        "'Svpbmt' (Page-Based Memory Types)">;
 
+// Pointer Masking extensions
+
+// A supervisor-level extension that provides pointer masking for the next lower
+// privilege mode (U-mode), and for VS- and VU-modes if the H extension is
+// present.
+def FeatureStdExtSsnpm
+    : SubtargetFeature<"experimental-ssnpm", "HasStdExtSsnpm", "true",
+                       "'Ssnpm' (Supervisor-level Pointer Masking for next lower privilege mode)">;
+
+// A machine-level extension that provides pointer masking for the next lower
+// privilege mode (S/HS if S-mode is implemented, or U-mode otherwise).
+def FeatureStdExtSmnpm
+    : SubtargetFeature<"experimental-smnpm", "HasStdExtSmnpm", "true",
+                       "'Smnpm' (Machine-level Pointer Masking for next lower privilege mode)">;
+
+// A machine-level extension that provides pointer masking for M-mode.
+def FeatureStdExtSmmpm
+    : SubtargetFeature<"experimental-smmpm", "HasStdExtSmmpm", "true",
+                       "'Smmpm' (Machine-level Pointer Masking for M-mode)">;
+
+// An extension that indicates that there is pointer-masking support available
+// in supervisor mode, with some facility provided in the supervisor execution
+// environment to control pointer masking.
+def FeatureStdExtSspm
+    : SubtargetFeature<"experimental-sspm", "HasStdExtSspm", "true",
+                       "'Sspm' (Indicates Supervisor-mode Pointer Masking)">;
+
+// An extension that indicates that there is pointer-masking support available
+// in user mode, with some facility provided in the application execution
+// environment to control pointer masking.
+def FeatureStdExtSupm
+    : SubtargetFeature<"experimental-supm", "HasStdExtSupm", "true",
+                       "'Supm' (Indicates User-mode Pointer Masking)">;
+
 //===----------------------------------------------------------------------===//
 // Vendor extensions
 //===----------------------------------------------------------------------===//

llvm/test/CodeGen/RISCV/attributes.ll

@@ -116,6 +116,11 @@
 ; RUN: llc -mtriple=riscv32 -mattr=+experimental-zalrsc %s -o - | FileCheck --check-prefix=RV32ZALRSC %s
 ; RUN: llc -mtriple=riscv32 -mattr=+experimental-zicfilp %s -o - | FileCheck --check-prefix=RV32ZICFILP %s
 ; RUN: llc -mtriple=riscv32 -mattr=+experimental-zabha %s -o - | FileCheck --check-prefix=RV32ZABHA %s
+; RUN: llc -mtriple=riscv32 -mattr=+experimental-ssnpm  %s -o - | FileCheck --check-prefix=RV32SSNPM %s
+; RUN: llc -mtriple=riscv32 -mattr=+experimental-smnpm  %s -o - | FileCheck --check-prefix=RV32SMNPM %s
+; RUN: llc -mtriple=riscv32 -mattr=+experimental-smmpm %s -o - | FileCheck --check-prefix=RV32SMMPM %s
+; RUN: llc -mtriple=riscv32 -mattr=+experimental-sspm %s -o - | FileCheck --check-prefix=RV32SSPM %s
+; RUN: llc -mtriple=riscv32 -mattr=+experimental-supm %s -o - | FileCheck --check-prefix=RV32SUPM %s
 
 ; RUN: llc -mtriple=riscv64 %s -o - | FileCheck %s
 ; RUN: llc -mtriple=riscv64 -mattr=+m %s -o - | FileCheck --check-prefixes=CHECK,RV64M %s
@@ -239,6 +244,11 @@
 ; RUN: llc -mtriple=riscv64 -mattr=+experimental-zalrsc %s -o - | FileCheck --check-prefix=RV64ZALRSC %s
 ; RUN: llc -mtriple=riscv64 -mattr=+experimental-zicfilp %s -o - | FileCheck --check-prefix=RV64ZICFILP %s
 ; RUN: llc -mtriple=riscv64 -mattr=+experimental-zabha %s -o - | FileCheck --check-prefix=RV64ZABHA %s
+; RUN: llc -mtriple=riscv64 -mattr=+experimental-ssnpm  %s -o - | FileCheck --check-prefix=RV64SSNPM %s
+; RUN: llc -mtriple=riscv64 -mattr=+experimental-smnpm  %s -o - | FileCheck --check-prefix=RV64SMNPM %s
+; RUN: llc -mtriple=riscv64 -mattr=+experimental-smmpm %s -o - | FileCheck --check-prefix=RV64SMMPM %s
+; RUN: llc -mtriple=riscv64 -mattr=+experimental-sspm %s -o - | FileCheck --check-prefix=RV64SSPM %s
+; RUN: llc -mtriple=riscv64 -mattr=+experimental-supm %s -o - | FileCheck --check-prefix=RV64SUPM %s
 
 ; CHECK: .attribute 4, 16
 
@@ -357,6 +367,11 @@
 ; RV32ZALRSC: .attribute 5, "rv32i2p1_zalrsc0p2"
 ; RV32ZICFILP: .attribute 5, "rv32i2p1_zicfilp0p4"
 ; RV32ZABHA: .attribute 5, "rv32i2p1_a2p1_zabha1p0"
+; RV32SSNPM: .attribute 5, "rv32i2p1_ssnpm0p8"
+; RV32SMNPM: .attribute 5, "rv32i2p1_smnpm0p8"
+; RV32SMMPM: .attribute 5, "rv32i2p1_smmpm0p8"
+; RV32SSPM: .attribute 5, "rv32i2p1_sspm0p8"
+; RV32SUPM: .attribute 5, "rv32i2p1_supm0p8"
 
 ; RV64M: .attribute 5, "rv64i2p1_m2p0"
 ; RV64ZMMUL: .attribute 5, "rv64i2p1_zmmul1p0"
@@ -479,6 +494,11 @@
 ; RV64ZALRSC: .attribute 5, "rv64i2p1_zalrsc0p2"
 ; RV64ZICFILP: .attribute 5, "rv64i2p1_zicfilp0p4"
 ; RV64ZABHA: .attribute 5, "rv64i2p1_a2p1_zabha1p0"
+; RV64SSNPM: .attribute 5, "rv64i2p1_ssnpm0p8"
+; RV64SMNPM: .attribute 5, "rv64i2p1_smnpm0p8"
+; RV64SMMPM: .attribute 5, "rv64i2p1_smmpm0p8"
+; RV64SSPM: .attribute 5, "rv64i2p1_sspm0p8"
+; RV64SUPM: .attribute 5, "rv64i2p1_supm0p8"
 
 define i32 @addi(i32 %a) {
   %1 = add i32 %a, 1

llvm/unittests/Support/RISCVISAInfoTest.cpp

@@ -881,6 +881,11 @@ Experimental extensions
     ztso                0.1
     zvfbfmin            1.0
     zvfbfwma            1.0
+    smmpm               0.8
+    smnpm               0.8
+    ssnpm               0.8
+    sspm                0.8
+    supm                0.8
 
 Use -march to specify the target's extension.
 For example, clang -march=rv32i_v1p0)";