nix-support: we can build with nix environment

.envrc

@@ -0,0 +1 @@
+use nix

.gitignore

@@ -6,4 +6,5 @@ run/
 bin
 cpu2006_build/
 Makefile.spec
-
+.cache/
+*/logs/*

README.md

@@ -76,6 +76,33 @@ make ARCH=riscv64 \
      build-all -j 29
 ```
 
+# Use Nix to build
+this repo can be built with nix, you do not need to warry about the dependencies.
+
+```shell
+// install nix
+sh <(curl -L https://nixos.org/nix/install) --no-daemon
+
+// prepare spec source
+export SPEC=/spec2006_path
+pushd $SPEC && source shrc && popd
+make copy-all-src
+
+// enter nix shell
+nix-shell
+
+// build
+make build-all -j 29
+```
+shell.nix is prepared to build with jemalloc, if you do not want to use jemalloc, 
+you can use shell_no_jemalloc.nix
+
+```shell
+nix-shell shell_no_jemalloc.nix
+// build
+make build-all -j 29
+```
+
 # Note for GCC >= 14
 
 The old version of xerces-c in 483.xalancbmk [contains a bug](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111544) that will cause compile errors in GCC 14 and later. You may need to apply the following patch to SPEC CPU 2006 source code to get this fixed:

shell.nix

@@ -0,0 +1,90 @@
+let
+  nixpkgs = fetchTarball {
+    url = "https://github.com/NixOS/nixpkgs/tarball/release-23.11";
+    sha256 = "sha256:1f5d2g1p6nfwycpmrnnmc2xmcszp804adp16knjvdkj8nz36y1fg";
+  };
+  pkgs = import nixpkgs {};
+  riscv64Pkgs = pkgs.pkgsCross.riscv64;
+
+  # Custom jemalloc with static libraries
+  customJemalloc = riscv64Pkgs.jemalloc.overrideAttrs (oldAttrs: {
+    configureFlags = (oldAttrs.configureFlags or []) ++ [
+      "--enable-static"
+      "--disable-shared"
+    ];
+    preBuild = ''
+      # Add weak attribute to C++ operators, 作用和jemalloc_cpp.patch效果一样
+      sed -i 's/void \*operator new(size_t)/void *operator new(size_t) __attribute__((weak))/g' src/jemalloc_cpp.cpp
+      sed -i 's/void operator delete(void \*)/void operator delete(void *) __attribute__((weak))/g' src/jemalloc_cpp.cpp
+    '';
+    # Ensure static libraries are installed
+    postInstall = ''
+      ${oldAttrs.postInstall or ""}
+      cp -v lib/libjemalloc.a $out/lib/
+    '';
+  });
+  riscv64Fortran = riscv64Pkgs.wrapCCWith {
+    cc = riscv64Pkgs.stdenv.cc.cc.override {
+      name = "gfortran";
+      langFortran = true;
+      langCC = false;
+      langC = false;
+      profiledCompiler = false;
+    };
+    # fixup wrapped prefix, which only appear if hostPlatform!=targetPlatform
+    #   for more details see <nixpkgs>/pkgs/build-support/cc-wrapper/default.nix
+    stdenvNoCC = riscv64Pkgs.stdenvNoCC.override {
+      hostPlatform = pkgs.stdenv.hostPlatform;
+    };
+  };
+  patchSPEC = let
+    rpath = pkgs.lib.makeLibraryPath [
+      pkgs.libxcrypt-legacy
+    ];
+  in pkgs.writeScriptBin "patchSPEC" ''
+    echo patching ''${SPEC:?env SPEC is not specified, fixupELFs aborted!}/bin
+
+    for file in $(find $SPEC/bin -type f \( -perm /0111 -o -name \*.so\* \) ); do
+      patchelf --set-interpreter "$(cat ${pkgs.stdenv.cc}/nix-support/dynamic-linker)" "$file" || true
+      patchelf --set-rpath ${rpath} $file || true
+    done
+
+    echo patchSPEC: done!
+  '';
+in
+
+pkgs.mkShell {
+  nativeBuildInputs = with pkgs; [
+    pkg-config
+    file
+    riscv64Pkgs.buildPackages.gcc
+    riscv64Pkgs.buildPackages.binutils
+    riscv64Fortran
+    patchSPEC
+  ];
+
+  buildInputs = with riscv64Pkgs; [
+    glibc
+    glibc.static
+    customJemalloc
+  ];
+
+  shellHook = ''
+    echo "Cross-compilation environment for RISC-V 64-bit (GNU) Linux with jemalloc ready"
+    echo "Use 'qemu-riscv64' to run the compiled program"
+
+    export SPEC_LITE=$PWD
+    export ARCH=riscv64
+    export CROSS_COMPILE=riscv64-unknown-linux-gnu-
+    export OPTIMIZE="-O3 -flto"
+    export SUBPROCESS_NUM=5
+
+    export CC=${riscv64Pkgs.stdenv.cc}/bin/riscv64-unknown-linux-gnu-gcc
+    export CXX=${riscv64Pkgs.stdenv.cc}/bin/riscv64-unknown-linux-gnu-g++
+    export LD=${riscv64Pkgs.stdenv.cc}/bin/riscv64-unknown-linux-gnu-ld
+
+    export CFLAGS="$CFLAGS -static -Wno-format-security -I${customJemalloc}/include "
+    export CXXFLAGS="$CXXFLAGS -static -Wno-format-security -I${customJemalloc}/include"
+    export LDFLAGS="$LDFLAGS -static -ljemalloc -L${customJemalloc}/lib"
+  '';
+}

shell_no_jemalloc.nix

@@ -0,0 +1,41 @@
+let
+  nixpkgs = fetchTarball {
+    url = "https://github.com/NixOS/nixpkgs/tarball/release-23.11";
+    sha256 = "sha256:1f5d2g1p6nfwycpmrnnmc2xmcszp804adp16knjvdkj8nz36y1fg";
+  };
+  pkgs = import nixpkgs {};
+  riscv64Pkgs = pkgs.pkgsCross.riscv64;
+in
+
+pkgs.mkShell {
+  nativeBuildInputs = with pkgs; [
+    pkg-config
+    file
+    riscv64Pkgs.buildPackages.gcc
+    riscv64Pkgs.buildPackages.binutils
+  ];
+
+  buildInputs = with riscv64Pkgs; [
+    glibc
+    glibc.static
+  ];
+
+  shellHook = ''
+    echo "Cross-compilation environment for RISC-V 64-bit (GNU) Linux ready"
+    echo "Use 'qemu-riscv64' to run the compiled program"
+
+    export SPEC_LITE=$PWD
+    export ARCH=riscv64
+    export CROSS_COMPILE=riscv64-unknown-linux-gnu-
+    export OPTIMIZE="-O3 -flto"
+    export SUBPROCESS_NUM=5
+
+    export CC=${riscv64Pkgs.stdenv.cc}/bin/riscv64-unknown-linux-gnu-gcc
+    export CXX=${riscv64Pkgs.stdenv.cc}/bin/riscv64-unknown-linux-gnu-g++
+    export LD=${riscv64Pkgs.stdenv.cc}/bin/riscv64-unknown-linux-gnu-ld
+
+    export CFLAGS="$CFLAGS -static -Wno-format-security"
+    export CXXFLAGS="$CXXFLAGS -static -Wno-format-security"
+    export LDFLAGS="$LDFLAGS -static"
+  '';
+}