[bug#54239] [PATCH 2/5] gnu: Add cross-clang.

[Julien Lepiller <julien@lepiller.eu>]

* gnu/packages/llvm.scm (cross-clang): New variable.
---
 gnu/packages/llvm.scm | 125 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 124 insertions(+), 1 deletion(-)

diff --git a/gnu/packages/llvm.scm b/gnu/packages/llvm.scm
index d6e9846699..c02f8e5c7a 100644
--- a/gnu/packages/llvm.scm
+++ b/gnu/packages/llvm.scm
@@ -54,6 +54,7 @@ (define-module (gnu packages llvm)
   #:use-module (guix build-system trivial)
   #:use-module (gnu packages)
   #:use-module (gnu packages base)
+  #:use-module (gnu packages cross-base)
   #:use-module (gnu packages gcc)
   #:use-module (gnu packages bootstrap)           ;glibc-dynamic-linker
   #:use-module (gnu packages check)               ;python-lit
@@ -75,7 +76,8 @@ (define-module (gnu packages llvm)
   #:use-module (ice-9 match)
   #:export (make-lld-wrapper
             system->llvm-target
-            cross-llvm))
+            cross-llvm
+            cross-clang))
 
 (define* (system->llvm-target #:optional
                               (system (or (and=> (%current-target-system)
@@ -1023,6 +1025,127 @@ (define-public clang-runtime clang-runtime-13)
 (define-public clang clang-13)
 (define-public clang-toolchain clang-toolchain-13)
 
+(define* (cross-clang target
+                      #:optional
+                      (libc (cross-libc target))
+                      (xgcc (cross-gcc target
+                              #:xbinutils (cross-binutils target)
+                              #:libc (cross-libc target)))
+                      (clang clang))
+  "Return a cross-clang compiler for target."
+  (package
+    (inherit clang)
+    (version (package-version clang))
+    ;; Support the same variables as clang, even in cross-compilation context.
+    ;; Clang does not make a difference between native and cross-compilation.
+    (search-paths
+     (append
+       (list
+         (search-path-specification
+           (variable "CROSS_LIBRARY_PATH")
+           (files '("lib" "lib64"))))
+       (package-native-search-paths clang)))
+    (native-search-paths '())
+    (arguments
+     (substitute-keyword-arguments (package-arguments clang)
+       ((#:configure-flags _)
+        `(list "-DCLANG_INCLUDE_TESTS=True"
+               (string-append "-DGCC_INSTALL_PREFIX="
+                              (assoc-ref %build-inputs "cross-gcc-lib"))
+               (string-append "-DC_INCLUDE_DIRS="
+                              (assoc-ref %build-inputs "target-libc")
+                              "/include")))
+       ((#:phases phases)
+        `(modify-phases ,phases
+           (add-after 'unpack 'add-missing-libdir
+             (lambda _
+               ;; cross-gcc installs its libraries in <target>/lib instead of
+               ;; lib.
+               (substitute* "lib/Driver/ToolChain.cpp"
+                 (("\"-L\"\\) \\+ LibPath\\)\\);")
+                  ,(string-append "\"-L\") + LibPath));
+  CmdArgs.push_back(Args.MakeArgString(StringRef(\"-L\") + "
+                                 "StringRef(GCC_INSTALL_PREFIX) + StringRef(\"/"
+                                 target "/lib\")));
+  CmdArgs.push_back(Args.MakeArgString(StringRef(\"-rpath=\") + "
+                                 "StringRef(GCC_INSTALL_PREFIX) + StringRef(\"/"
+                                 target "/lib\")));")))))
+           (add-after 'unpack 'support-cross-library-path
+             (lambda _
+               ;; LIBRARY_PATH is only supported for native builds, but we still
+               ;; need it (or CROSS_LIBRARY_PATH to be precise) when
+               ;; cross-compiling
+               (substitute* "lib/Driver/ToolChains/CommonArgs.cpp"
+                 (("LIBRARY_PATH\"")
+                  "LIBRARY_PATH\");
+  } else {
+    addDirectoryList(Args, CmdArgs, \"-L\", \"CROSS_LIBRARY_PATH\""))))
+           (replace 'set-glibc-file-names
+             (lambda* (#:key inputs #:allow-other-keys)
+               (let ((libc (assoc-ref inputs "target-libc"))
+                     (compiler-rt (assoc-ref inputs "clang-runtime"))
+                     (gcc (assoc-ref inputs "cross-gcc")))
+                 (setenv "LIBRARY_PATH"
+                         (string-append
+                           (assoc-ref inputs "libc") "/lib:" (getenv "LIBRARY_PATH")))
+                 ,@(cond
+                    ((version>=? version "6.0")
+                     `(;; Link to libclang_rt files from clang-runtime.
+                       (substitute* "lib/Driver/ToolChain.cpp"
+                         (("getDriver\\(\\)\\.ResourceDir")
+                          (string-append "\"" compiler-rt "\"")))
+
+                       ;; Make "LibDir" refer to <glibc>/lib so that it
+                       ;; uses the right dynamic linker file name.
+                       (substitute* "lib/Driver/ToolChains/Linux.cpp"
+                         (("(^[[:blank:]]+LibDir = ).*" _ declaration)
+                          (string-append declaration "\"" libc "/lib\";\n"))
+
+                         ;; Make clang look for libstdc++ in the right
+                         ;; location.
+                         (("LibStdCXXIncludePathCandidates\\[\\] = \\{")
+                          (string-append
+                           "LibStdCXXIncludePathCandidates[] = { \"" gcc
+                           "/include/c++\","))
+
+                         ;; Make sure libc's libdir is on the search path, to
+                         ;; allow crt1.o & co. to be found.
+                         (("@GLIBC_LIBDIR@")
+                          (string-append libc "/lib")))))
+                    (else
+                     `((substitute* "lib/Driver/Tools.cpp"
+                         ;; Patch the 'getLinuxDynamicLinker' function so that
+                         ;; it uses the right dynamic linker file name.
+                         (("/lib64/ld-linux-x86-64.so.2")
+                          (string-append libc ,(glibc-dynamic-linker))))
+
+                       ;; Link to libclang_rt files from clang-runtime.
+                       ;; This substitution needed slight adjustment in 3.8.
+                       ,@(if (version>=? version "3.8")
+                             '((substitute* "lib/Driver/Tools.cpp"
+                                 (("TC\\.getDriver\\(\\)\\.ResourceDir")
+                                  (string-append "\"" compiler-rt "\""))))
+                             '((substitute* "lib/Driver/ToolChain.cpp"
+                                 (("getDriver\\(\\)\\.ResourceDir")
+                                  (string-append "\"" compiler-rt "\"")))))
+
+                       ;; Make sure libc's libdir is on the search path, to
+                       ;; allow crt1.o & co. to be found.
+                       (substitute* "lib/Driver/ToolChains.cpp"
+                         (("@GLIBC_LIBDIR@")
+                          (string-append libc "/lib")))))))))))))
+    (inputs
+     `(("target-libc" ,libc)
+       ("cross-gcc-lib" ,xgcc "lib")
+       ("cross-gcc" ,xgcc)
+       ,@(package-inputs clang)))
+    (propagated-inputs
+      (modify-inputs (package-propagated-inputs clang)
+        (replace "llvm"
+          (cross-llvm
+            (car (assoc-ref (package-propagated-inputs clang) "llvm"))
+            target))))))
+
 (define-public llvm-for-rocm
   (package
     ;; Actually based on LLVM 13 as of v4.3, but llvm-12 works just fine.
-- 
2.34.0