Add RISC-V 64-bit JIT backend, tests, and CI integration

Implement jit_riscv64.erl backend with full JIT compilation support:
- RV64IMAC calling convention (a0=context, s1-s11 callee-saved)
- All required backend exports (new, stream, call_primitive,
  move_to_native_register, jump_to_label, cond_jump_to_label, etc.)
- Register value caching to avoid redundant loads
- Branch patching with compressed instruction support
- DWARF debug info integration (jit_dwarf.erl machine type,
  jit_dwarf.hrl register constant)

C-side integration:
- Architecture detection in jit.h (__riscv with __riscv_xlen == 64)
- Struct offset static assertions in jit.c
- Atom registration for riscv64 in nifs.c and defaultatoms.def
- CMake JIT_TARGET_ARCH=riscv64 support

CI pipeline:
- Cross-compiled plain, JIT, and JIT+DWARF builds
- Uses crossbuild-essential-riscv64 with QEMU user emulation

Test infrastructure:
- jit_riscv64_tests.erl for backend operation tests
- jit_tests_common.erl binutils support for riscv64-linux-gnu
- Registration in tests.erl and CMakeLists.txt

Author: claude

.github/workflows/build-and-test.yaml

@@ -411,6 +411,47 @@ jobs:
           arch: "s390x"
           library-arch: s390x-linux-gnu
 
+        # riscv64 build
+        - os: "ubuntu-24.04"
+          cc: "riscv64-linux-gnu-gcc"
+          cxx: "riscv64-linux-gnu-g++"
+          cflags: "-O2"
+          otp: "28"
+          elixir_version: "1.17"
+          rebar3_version: "3.24.0"
+          cmake_opts_other: "-DAVM_WARNINGS_ARE_ERRORS=ON -DCMAKE_TOOLCHAIN_FILE=${RUNNER_TEMP}/riscv64_toolchain.cmake"
+          compiler_pkgs: "crossbuild-essential-riscv64 libc6-dbg:riscv64 zlib1g-dev:riscv64 libmbedtls-dev:riscv64 qemu-user qemu-user-binfmt binfmt-support"
+          arch: "riscv64"
+          library-arch: riscv64-linux-gnu
+
+        # riscv64 build + jit
+        - os: "ubuntu-24.04"
+          cc: "riscv64-linux-gnu-gcc"
+          cxx: "riscv64-linux-gnu-g++"
+          cflags: "-O2"
+          otp: "28"
+          elixir_version: "1.17"
+          rebar3_version: "3.24.0"
+          cmake_opts_other: "-DAVM_DISABLE_JIT=OFF -DAVM_JIT_TARGET_ARCH=riscv64 -DCMAKE_TOOLCHAIN_FILE=${RUNNER_TEMP}/riscv64_toolchain.cmake"
+          compiler_pkgs: "crossbuild-essential-riscv64 libc6-dbg:riscv64 zlib1g-dev:riscv64 libmbedtls-dev:riscv64 qemu-user qemu-user-binfmt binfmt-support"
+          arch: "riscv64"
+          library-arch: riscv64-linux-gnu
+          jit_target_arch: "riscv64"
+
+        # JIT + DWARF build (riscv64)
+        - os: "ubuntu-24.04"
+          cc: "riscv64-linux-gnu-gcc"
+          cxx: "riscv64-linux-gnu-g++"
+          cflags: "-O2"
+          otp: "28"
+          elixir_version: "1.17"
+          rebar3_version: "3.24.0"
+          cmake_opts_other: "-DAVM_DISABLE_JIT=OFF -DAVM_DISABLE_JIT_DWARF=OFF -DAVM_JIT_TARGET_ARCH=riscv64 -DCMAKE_TOOLCHAIN_FILE=${RUNNER_TEMP}/riscv64_toolchain.cmake"
+          compiler_pkgs: "crossbuild-essential-riscv64 libc6-dbg:riscv64 zlib1g-dev:riscv64 libmbedtls-dev:riscv64 qemu-user qemu-user-binfmt binfmt-support"
+          arch: "riscv64"
+          library-arch: riscv64-linux-gnu
+          jit_target_arch: "riscv64"
+
         # riscv32-ilp32 build
         - os: "ubuntu-24.04"
           cc: "riscv32-unknown-linux-gnu-gcc"

CMakeLists.txt

@@ -61,12 +61,14 @@ if (NOT AVM_DISABLE_JIT AND NOT DEFINED AVM_JIT_TARGET_ARCH)
         set(AVM_JIT_TARGET_ARCH "aarch64")
     elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^cortex-m.+$")
         set(AVM_JIT_TARGET_ARCH "armv6m")
+    elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^riscv64$")
+        set(AVM_JIT_TARGET_ARCH "riscv64")
     else()
         message(FATAL_ERROR "JIT is not supported on ${CMAKE_SYSTEM_PROCESSOR}")
     endif()
 endif()
 
-set(AVM_PRECOMPILED_TARGETS "x86_64;aarch64;armv6m;armv6m+float32;riscv32" CACHE STRING "Targets to precompile code to if AVM_DISABLE_JIT is OFF or AVM_ENABLE_PRECOMPILED is ON")
+set(AVM_PRECOMPILED_TARGETS "x86_64;aarch64;armv6m;armv6m+float32;riscv32;riscv64" CACHE STRING "Targets to precompile code to if AVM_DISABLE_JIT is OFF or AVM_ENABLE_PRECOMPILED is ON")
 
 if((${CMAKE_SYSTEM_NAME} STREQUAL "Darwin") OR
    (${CMAKE_SYSTEM_NAME} STREQUAL "Linux") OR

libs/jit/include/jit.hrl

@@ -28,6 +28,7 @@
 -define(JIT_ARCH_AARCH64, 2).
 -define(JIT_ARCH_ARMV6M, 3).
 -define(JIT_ARCH_RISCV32, 4).
+-define(JIT_ARCH_RISCV64, 5).
 
 -define(JIT_VARIANT_PIC, 1).
 -define(JIT_VARIANT_FLOAT32, 2).

libs/jit/src/CMakeLists.txt

@@ -36,6 +36,8 @@ set(ERLANG_MODULES
     jit_armv6m_asm
     jit_riscv32
     jit_riscv32_asm
+    jit_riscv64
+    jit_riscv64_asm
     jit_x86_64
     jit_x86_64_asm
 )

libs/jit/src/jit_dwarf.erl

@@ -343,7 +343,8 @@ elf(_State, _NativeCode) ->
 backend_to_machine_type(jit_x86_64) -> ?EM_X86_64;
 backend_to_machine_type(jit_aarch64) -> ?EM_AARCH64;
 backend_to_machine_type(jit_armv6m) -> ?EM_ARM;
-backend_to_machine_type(jit_riscv32) -> ?EM_RISCV.
+backend_to_machine_type(jit_riscv32) -> ?EM_RISCV;
+backend_to_machine_type(jit_riscv64) -> ?EM_RISCV.
 
 %% Map JIT backend to ELF flags
 backend_to_elf_flags(jit_armv6m) ->

libs/jit/src/jit_dwarf.hrl

@@ -105,5 +105,6 @@
 -define(DWARF_X0_REG_AARCH64, 0).
 % a0 register in RISC-V
 -define(DWARF_A0_REG_RISCV32, 10).
+-define(DWARF_A0_REG_RISCV64, 10).
 % r0 register in ARM
 -define(DWARF_R0_REG_ARMV6M, 0).

libs/jit/src/jit_precompile.erl

@@ -119,6 +119,7 @@ compile(Target, Dir, Dwarf, Path) ->
                 "aarch64" -> ?JIT_ARCH_AARCH64;
                 "armv6m" -> ?JIT_ARCH_ARMV6M;
                 "riscv32" -> ?JIT_ARCH_RISCV32;
+                "riscv64" -> ?JIT_ARCH_RISCV64;
                 _ -> error({unsupported_target, Target})
             end,