Initial support for RISC-V (JuliaLang#56105)

Rebase and extension of @alexfanqi's initial work on porting Julia to RISC-V. Requires LLVM 19. Tested on a VisionFive2, built with: ```make MARCH := rv64gc_zba_zbb MCPU := sifive-u74 USE_BINARYBUILDER:=0 DEPS_GIT = llvm override LLVM_VER=19.1.1 override LLVM_BRANCH=julia-release/19.x override LLVM_SHA1=julia-release/19.x ``` ```julia-repl ❯ ./julia _ _ _ _(_)_ | Documentation: https://docs.julialang.org (_) | (_) (_) | _ _ _| |_ __ _ | Type "?" for help, "]?" for Pkg help. | | | | | | |/ _` | | | | |_| | | | (_| | | Version 1.12.0-DEV.1374 (2024-10-14) _/ |\__'_|_|_|\__'_| | riscv/25092a3982* (fork: 1 commits, 0 days) |__/ | julia> versioninfo(; verbose=true) Julia Version 1.12.0-DEV.1374 Commit 25092a3* (2024-10-14 09:57 UTC) Platform Info: OS: Linux (riscv64-unknown-linux-gnu) uname: Linux 6.11.3-1-riscv64 #1 SMP Debian 6.11.3-1 (2024-10-10) riscv64 unknown CPU: unknown: speed user nice sys idle irq #1 1500 MHz 922 s 0 s 265 s 160953 s 0 s #2 1500 MHz 457 s 0 s 280 s 161521 s 0 s #3 1500 MHz 452 s 0 s 270 s 160911 s 0 s #4 1500 MHz 638 s 15 s 301 s 161340 s 0 s Memory: 7.760246276855469 GB (7474.08203125 MB free) Uptime: 16260.13 sec Load Avg: 0.25 0.23 0.1 WORD_SIZE: 64 LLVM: libLLVM-19.1.1 (ORCJIT, sifive-u74) Threads: 1 default, 0 interactive, 1 GC (on 4 virtual cores) Environment: HOME = /home/tim PATH = /home/tim/.local/bin:/usr/local/bin:/usr/bin:/bin:/usr/games TERM = xterm-256color julia> ccall(:jl_dump_host_cpu, Nothing, ()) CPU: sifive-u74 Features: +zbb,+d,+i,+f,+c,+a,+zba,+m,-zvbc,-zksed,-zvfhmin,-zbkc,-zkne,-zksh,-zfh,-zfhmin,-zknh,-v,-zihintpause,-zicboz,-zbs,-zvknha,-zvksed,-zfa,-ztso,-zbc,-zvknhb,-zihintntl,-zknd,-zvbb,-zbkx,-zkt,-zvkt,-zicond,-zvksh,-zvfh,-zvkg,-zvkb,-zbkb,-zvkned julia> @code_native debuginfo=:none 1+2. .text .attribute 4, 16 .attribute 5, "rv64i2p1_m2p0_a2p1_f2p2_d2p2_c2p0_zicsr2p0_zifencei2p0_zmmul1p0_zba1p0_zbb1p0" .file "+" .globl "julia_+_3003" .p2align 1 .type "julia_+_3003",@function "julia_+_3003": addi sp, sp, -16 sd ra, 8(sp) sd s0, 0(sp) addi s0, sp, 16 fcvt.d.l fa5, a0 ld ra, 8(sp) ld s0, 0(sp) fadd.d fa0, fa5, fa0 addi sp, sp, 16 ret .Lfunc_end0: .size "julia_+_3003", .Lfunc_end0-"julia_+_3003" .type ".L+Core.Float64#3005",@object .section .data.rel.ro,"aw",@progbits .p2align 3, 0x0 ".L+Core.Float64#3005": .quad ".L+Core.Float64#3005.jit" .size ".L+Core.Float64#3005", 8 .set ".L+Core.Float64#3005.jit", 272467692544 .size ".L+Core.Float64#3005.jit", 8 .section ".note.GNU-stack","",@progbits ``` Lots of bugs guaranteed, but with this we at least have a functional build and REPL for further development by whoever is interested. Also requires Linux 6.4+, since the fallback processor detection used here relies on LLVM's `sys::getHostCPUFeatures`, which for RISC-V is implemented using hwprobe introduced in 6.4. We could probably add a fallback that parses `/proc/cpuinfo`, either by building a CPU database much like how we've done for AArch64, or by parsing the actual ISA string contained there. That would probably also be a good place to add support for profiles, which are supposedly the way forward to package RISC-V binaries. That can happen in follow-up PRs though. For now, on older kernels, use the `-C` arg to Julia to specify an ISA. Co-authored-by: Alex Fan <alex.fan.q@gmail.com>
N5N3 · Oct 16, 2024 · a98f371 · a98f371
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diff --git a/Make.inc b/Make.inc
@@ -938,8 +938,12 @@ endif
 
 #If nothing is set default to native unless we are cross-compiling
 ifeq ($(MARCH)$(MCPU)$(MTUNE)$(JULIA_CPU_TARGET)$(XC_HOST),)
-ifeq ($(ARCH),aarch64) #ARM recommends only setting MCPU for AArch64
+ifeq ($(ARCH),aarch64)
+# ARM recommends only setting MCPU for AArch64
 MCPU=native
+else ifneq (,$(findstring riscv64,$(ARCH)))
+# RISC-V doesn't have a native option
+$(error Building for RISC-V requires a specific MARCH to be set))
 else
 MARCH=native
 MTUNE=native
@@ -995,6 +999,9 @@ endif
 ifneq (,$(findstring arm,$(ARCH)))
 DIST_ARCH:=arm
 endif
+ifneq (,$(findstring riscv64,$(ARCH)))
+DIST_ARCH:=riscv64
+endif
 
 JULIA_BINARYDIST_FILENAME := julia-$(JULIA_COMMIT)-$(DIST_OS)$(DIST_ARCH)
 endif
@@ -1018,8 +1025,12 @@ ifneq ($(MARCH),)
 CC += -march=$(MARCH)
 CXX += -march=$(MARCH)
 FC += -march=$(MARCH)
+# On RISC-V, don't forward the MARCH ISA string to JULIA_CPU_TARGET,
+# as it's always incompatible with LLVM's CPU target name parser.
+ifeq (,$(findstring riscv64,$(ARCH)))
 JULIA_CPU_TARGET ?= $(MARCH)
 endif
+endif
 
 # Set MCPU-specific flags
 ifneq ($(MCPU),)

diff --git a/base/binaryplatforms.jl b/base/binaryplatforms.jl
@@ -597,7 +597,7 @@ const arch_mapping = Dict(
     "armv7l" => "arm(v7l)?", # if we just see `arm-linux-gnueabihf`, we assume it's `armv7l`
     "armv6l" => "armv6l",
     "powerpc64le" => "p(ower)?pc64le",
-    "riscv64" => "riscv64",
+    "riscv64" => "(rv64|riscv64)",
 )
 # Keep this in sync with `CPUID.ISAs_by_family`
 # These are the CPUID side of the microarchitectures targeted by GCC flags in BinaryBuilder.jl
@@ -631,6 +631,9 @@ const arch_march_isa_mapping = let
             "a64fx" => get_set("aarch64", "a64fx"),
             "apple_m1" => get_set("aarch64", "apple_m1"),
         ],
+        "riscv64" => [
+            "riscv64" => get_set("riscv64", "riscv64")
+        ],
         "powerpc64le" => [
             "power8" => get_set("powerpc64le", "power8"),
         ],

diff --git a/base/cpuid.jl b/base/cpuid.jl
@@ -61,6 +61,9 @@ const ISAs_by_family = Dict(
         "a64fx" => ISA(Set((JL_AArch64_v8_2a, JL_AArch64_lse, JL_AArch64_crc, JL_AArch64_rdm, JL_AArch64_sha2, JL_AArch64_ccpp, JL_AArch64_complxnum, JL_AArch64_fullfp16, JL_AArch64_sve))),
         "apple_m1" => ISA(Set((JL_AArch64_v8_5a, JL_AArch64_lse, JL_AArch64_crc, JL_AArch64_rdm, JL_AArch64_aes, JL_AArch64_sha2, JL_AArch64_sha3, JL_AArch64_ccpp, JL_AArch64_complxnum, JL_AArch64_fp16fml, JL_AArch64_fullfp16, JL_AArch64_dotprod, JL_AArch64_rcpc, JL_AArch64_altnzcv))),
     ],
+    "riscv64" => [
+        "riscv64" => ISA(Set{UInt32}()),
+    ],
     "powerpc64le" => [
         # We have no way to test powerpc64le features yet, so we're only going to declare the lowest ISA:
         "power8" => ISA(Set{UInt32}()),

diff --git a/cli/trampolines/trampolines_riscv64.S b/cli/trampolines/trampolines_riscv64.S
@@ -0,0 +1,20 @@
+// This file is a part of Julia. License is MIT: https://julialang.org/license
+
+#include "common.h"
+#include "../../src/jl_exported_funcs.inc"
+
+#define SEP ;
+
+#define XX(name) \
+.global CNAME(name) SEP \
+.cfi_startproc SEP \
+.p2align    2 SEP \
+ CNAME(name)##: SEP \
+    auipc t3, %pcrel_hi(CNAMEADDR(name)) SEP \
+    ld t3, %pcrel_lo(CNAME(name))(t3) SEP \
+    jr t3 SEP \
+.cfi_endproc SEP \
+
+JL_RUNTIME_EXPORTED_FUNCS(XX)
+JL_CODEGEN_EXPORTED_FUNCS(XX)
+#undef XX
diff --git a/contrib/generate_precompile.jl b/contrib/generate_precompile.jl
@@ -202,12 +202,15 @@ if Artifacts !== nothing
     using Artifacts, Base.BinaryPlatforms, Libdl
     artifacts_toml = abspath(joinpath(Sys.STDLIB, "Artifacts", "test", "Artifacts.toml"))
     artifact_hash("HelloWorldC", artifacts_toml)
-    oldpwd = pwd(); cd(dirname(artifacts_toml))
-    macroexpand(Main, :(@artifact_str("HelloWorldC")))
-    cd(oldpwd)
     artifacts = Artifacts.load_artifacts_toml(artifacts_toml)
     platforms = [Artifacts.unpack_platform(e, "HelloWorldC", artifacts_toml) for e in artifacts["HelloWorldC"]]
     best_platform = select_platform(Dict(p => triplet(p) for p in platforms))
+    if best_platform !== nothing
+      # @artifact errors for unsupported platforms
+      oldpwd = pwd(); cd(dirname(artifacts_toml))
+      macroexpand(Main, :(@artifact_str("HelloWorldC")))
+      cd(oldpwd)
+    end
     dlopen("libjulia$(Base.isdebugbuild() ? "-debug" : "")", RTLD_LAZY | RTLD_DEEPBIND)
     """
 end

diff --git a/contrib/normalize_triplet.py b/contrib/normalize_triplet.py
@@ -14,6 +14,7 @@
     'i686': "i\\d86",
     'aarch64': "(arm|aarch)64",
     'armv7l': "arm(v7l)?",
+    'riscv64': "(rv64|riscv64)",
     'powerpc64le': "p(ower)?pc64le",
 }
 platform_mapping = {

diff --git a/doc/src/devdocs/build/build.md b/doc/src/devdocs/build/build.md
@@ -148,6 +148,7 @@ Notes for various operating systems:
 Notes for various architectures:
 
 * [ARM](https://github.com/JuliaLang/julia/blob/master/doc/src/devdocs/build/arm.md)
+* [RISC-V](https://github.com/JuliaLang/julia/blob/master/doc/src/devdocs/build/riscv.md)
 
 ## Required Build Tools and External Libraries
 

diff --git a/doc/src/devdocs/build/riscv.md b/doc/src/devdocs/build/riscv.md
@@ -0,0 +1,103 @@
+# RISC-V (Linux)
+
+Julia has experimental support for 64-bit RISC-V (RV64) processors running
+Linux. This file provides general guidelines for compilation, in addition to
+instructions for specific devices.
+
+A list of [known issues](https://github.com/JuliaLang/julia/labels/system:riscv)
+for RISC-V is available. If you encounter difficulties, please create an issue
+including the output from `cat /proc/cpuinfo`.
+
+
+## Compiling Julia
+
+For now, Julia will need to be compiled entirely from source, i.e., including
+all of its dependencies. This can be accomplished with the following
+`Make.user`:
+
+```make
+USE_BINARYBUILDER := 0
+```
+
+Additionally, it is required to indicate what architecture, and optionally which
+CPU to build for. This can be done by setting the `MARCH` and `MCPU` variables
+in `Make.user`
+
+The `MARCH` variable needs to be set to a RISC-V ISA string, which can be found by
+looking at the documentation of your device, or by inspecting `/proc/cpuinfo`. Only
+use flags that your compiler supports, e.g., run `gcc -march=help` to see a list of
+supported flags. A common value is `rv64gc`, which is a good starting point.
+
+The `MCPU` variable is optional, and can be used to further optimize the
+generated code for a specific CPU. If you are unsure, it is recommended to leave
+it unset. You can find a list of supported values by running `gcc --target-help`.
+
+For example, if you are using a StarFive VisionFive2, which contains a JH7110
+processor based on the SiFive U74, you can set these flags as follows:
+
+```make
+MARCH := rv64gc_zba_zbb
+MCPU := sifive-u74
+```
+
+If you prefer a portable build, you could use:
+
+```make
+MARCH := rv64gc
+
+# also set JULIA_CPU_TARGET to the expanded form of rv64gc
+# (it normally copies the value of MCPU, which we don't set)
+JULIA_CPU_TARGET := generic-rv64,i,m,a,f,d,zicsr,zifencei,c
+```
+
+### Cross-compilation
+
+A native build on a RISC-V device may take a very long time, so it's also
+possible to cross-compile Julia on a faster machine.
+
+First, get a hold of a RISC-V cross-compilation toolchain that provides
+support for C, C++ and Fortran. This can be done by checking-out the
+[riscv-gnu-toolchain](https://github.com/riscv-collab/riscv-gnu-toolchain)
+repository and building it as follows:
+
+```sh
+sudo mkdir /opt/riscv && sudo chown $USER /opt/riscv
+./configure --prefix=/opt/riscv --with-languages=c,c++,fortran
+make linux -j$(nproc)
+```
+
+Then, install the QEMU user-mode emulator for RISC-V, along with `binfmt`
+support to enable execution of RISC-V binaries on the host machine. The
+exact steps depend on your distribution, e.g., on Arch Linux it involves
+installing the `qemu-user-static` and `qemu-user-static-binfmt` packages.
+Note that to actually execute RISC-V binaries, QEMU will need to be able to
+find the RISC-V system root, which can be achieved by setting the
+`QEMU_LD_PREFIX` environment variable to the path of the root filesystem.
+
+Finally, compile Julia with the following `Make.user` variables (in addition to
+the ones from the previous section):
+
+```make
+XC_HOST=riscv64-unknown-linux-gnu
+OS=Linux
+export QEMU_LD_PREFIX=/opt/riscv/sysroot
+```
+
+Note that you will have to execute `make` with `PATH` set to include the
+cross-compilation toolchain, e.g., by running:
+
+```sh
+PATH=/opt/riscv/bin:$PATH make -j$(nproc)
+```
+
+Because of the RISC-V sysroot we use being very barren, you may need to
+add additional libraries that the Julia build system currently expects
+to be available system-wide. For example, the build currently relies on
+a system-provided `libz`, so you may need to copy this library from the
+Julia build into the system root:
+
+```sh
+make -C deps install-zlib
+cp -v usr/lib/libz.*   /opt/riscv/sysroot/usr/lib
+cp -v usr/include/z*.h /opt/riscv/sysroot/usr/include
+```