gnu: Add llvm-13.

* gnu/packages/llvm.scm (llvm-13, clang-runtime-13, clang-13,
clang-toolchain-13): New variables.
(llvm-12): Inherit from llvm-13.
* gnu/packages/patches/clang-13.0-libc-search-path.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.

gnu/local.mk

@@ -946,6 +946,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/clang-10.0-libc-search-path.patch	\
   %D%/packages/patches/clang-11.0-libc-search-path.patch	\
   %D%/packages/patches/clang-12.0-libc-search-path.patch	\
+  %D%/packages/patches/clang-13.0-libc-search-path.patch	\
   %D%/packages/patches/clang-runtime-asan-build-fixes.patch	\
   %D%/packages/patches/clang-runtime-esan-build-fixes.patch	\
   %D%/packages/patches/clang-runtime-9-libsanitizer-mode-field.patch	\

gnu/packages/llvm.scm

@@ -486,17 +486,17 @@ (define (make-clang-toolchain clang)
               ("libc-debug" ,glibc "debug")
               ("libc-static" ,glibc "static")))))
 
-(define-public llvm-12
+(define-public llvm-13
   (package
     (name "llvm")
-    (version "12.0.1")
+    (version "13.0.0")
     (source
      (origin
       (method url-fetch)
       (uri (llvm-uri "llvm" version))
       (sha256
        (base32
-        "1pzx9zrmd7r3481sbhwvkms68fwhffpp4mmz45dgrkjpyl2q96kx"))))
+        "081h2vw757j5xjg2441539j2vhfzzihrgxwza5pq5sj3hrq133a0"))))
     (build-system cmake-build-system)
     (outputs '("out" "opt-viewer"))
     (native-inputs
@@ -506,6 +506,97 @@ (define-public llvm-12
      (list libffi))
     (propagated-inputs
      (list zlib))                 ;to use output from llvm-config
+    (arguments
+     ;; TODO(core-updates): Unconditionally use quasiquote
+     `(#:configure-flags
+       ,#~(#$(if (%current-target-system)
+                 #~quasiquote
+                 #~quote)
+           ;; These options are required for cross-compiling LLVM according to
+           ;; https://llvm.org/docs/HowToCrossCompileLLVM.html.
+           (#$@(if (%current-target-system)
+                   #~(,(string-append "-DLLVM_TABLEGEN="
+                                      #+(file-append this-package
+                                                     "/bin/llvm-tblgen"))
+                      #$(string-append "-DLLVM_DEFAULT_TARGET_TRIPLE="
+                                       (%current-target-system))
+                      #$(string-append "-DLLVM_TARGET_ARCH="
+                                       (system->llvm-target))
+                      #$(string-append "-DLLVM_TARGETS_TO_BUILD="
+                                       (system->llvm-target)))
+                   #~())
+            "-DCMAKE_SKIP_BUILD_RPATH=FALSE"
+            "-DCMAKE_BUILD_WITH_INSTALL_RPATH=FALSE"
+            "-DBUILD_SHARED_LIBS:BOOL=TRUE"
+            "-DLLVM_ENABLE_FFI:BOOL=TRUE"
+            "-DLLVM_REQUIRES_RTTI=1" ; For some third-party utilities
+            "-DLLVM_INSTALL_UTILS=ON")) ; Needed for rustc.
+       ;; Don't use '-g' during the build, to save space.
+       #:build-type "Release"
+       #:phases
+       (modify-phases %standard-phases
+         (add-after 'install 'install-opt-viewer
+           (lambda* (#:key outputs #:allow-other-keys)
+             (let* ((out (assoc-ref outputs "out"))
+                    (opt-viewer-out (assoc-ref outputs "opt-viewer"))
+                    (opt-viewer-share-dir (string-append opt-viewer-out "/share"))
+                    (opt-viewer-dir (string-append opt-viewer-share-dir "/opt-viewer")))
+               (mkdir-p opt-viewer-share-dir)
+               (rename-file (string-append out "/share/opt-viewer")
+                            opt-viewer-dir)))))))
+    (home-page "https://www.llvm.org")
+    (synopsis "Optimizing compiler infrastructure")
+    (description
+     "LLVM is a compiler infrastructure designed for compile-time, link-time,
+runtime, and idle-time optimization of programs from arbitrary programming
+languages.  It currently supports compilation of C and C++ programs, using
+front-ends derived from GCC 4.0.1.  A new front-end for the C family of
+languages is in development.  The compiler infrastructure includes mirror sets
+of programming tools as well as libraries with equivalent functionality.")
+    (license license:asl2.0)))
+
+(define-public clang-runtime-13
+  (clang-runtime-from-llvm
+   llvm-13
+   "0gyvfhnypfmlf7hdgkiz2wh2lgk4nz26aqf361msjs3qdkbh4djc"))
+
+(define-public clang-13
+  (let ((template
+         (clang-from-llvm llvm-13 clang-runtime-13
+                          "0zp1p6syii5iajm8v2c207s80arv00yz5ckfwimn5dng0sxiqqax"
+                          #:patches '("clang-13.0-libc-search-path.patch")
+                          #:tools-extra
+                          (origin
+                            (method url-fetch)
+                            (uri (llvm-uri "clang-tools-extra"
+                                           (package-version llvm-13)))
+                            (sha256
+                             (base32
+                              "1mgalgdgxlxi08yxw7k6yh4iia1bpjmjgn7mrpqas8lbl9h612s2"))))))
+    (package
+      (inherit template)
+      (arguments
+       (substitute-keyword-arguments (package-arguments template)
+         ((#:phases phases '%standard-phases)
+          `(modify-phases ,phases
+             ;; This fails because the target to
+             ;; lib/clang/13.0.0/share/cfi_blacklist.txt is not found.
+             (delete 'validate-runpath))))))))
+
+(define-public clang-toolchain-13
+  (make-clang-toolchain clang-13))
+
+(define-public llvm-12
+  (package
+    (inherit llvm-13)
+    (version "12.0.1")
+    (source
+     (origin
+      (method url-fetch)
+      (uri (llvm-uri "llvm" version))
+      (sha256
+       (base32
+        "1pzx9zrmd7r3481sbhwvkms68fwhffpp4mmz45dgrkjpyl2q96kx"))))
     (arguments
      ;; TODO(core-updates): Unconditionally use quasiquote
      `(#:configure-flags
@@ -553,17 +644,7 @@ (define-public llvm-12
                (mkdir-p opt-viewer-share-dir)
                (rename-file (string-append out "/share/opt-viewer")
                             opt-viewer-dir))
-             #t)))))
+             #t)))))))
-    (home-page "https://www.llvm.org")
-    (synopsis "Optimizing compiler infrastructure")
-    (description
-     "LLVM is a compiler infrastructure designed for compile-time, link-time,
-runtime, and idle-time optimization of programs from arbitrary programming
-languages.  It currently supports compilation of C and C++ programs, using
-front-ends derived from GCC 4.0.1.  A new front-end for the C family of
-languages is in development.  The compiler infrastructure includes mirror sets
-of programming tools as well as libraries with equivalent functionality.")
-    (license license:asl2.0)))  ;with LLVM exceptions, see LICENSE.txt
 
 (define-public clang-runtime-12
   (clang-runtime-from-llvm

gnu/packages/patches/clang-13.0-libc-search-path.patch

@@ -0,0 +1,96 @@
+Clang attempts to guess file names based on the OS and distro (yes!),
+but unfortunately, that doesn't work for us.
+
+This patch makes it easy to insert libc's $libdir so that Clang passes the
+correct absolute file name of crt1.o etc. to 'ld'.  It also disables all
+the distro-specific stuff and removes the hard-coded FHS directory names
+to make sure Clang also works on foreign distros.
+
+diff --git a/lib/Driver/Distro.cpp b/lib/Driver/Distro.cpp
+index ee4fe841..f0313bbe 100644
+--- a/lib/Driver/Distro.cpp
++++ b/lib/Driver/Distro.cpp
+@@ -93,6 +93,10 @@ static Distro::DistroType DetectLsbRelease(llvm::vfs::FileSystem &VFS) {
+ }
+ 
+ static Distro::DistroType DetectDistro(llvm::vfs::FileSystem &VFS) {
++  // The compiler should always behave the same, even when used via Guix on a
++  // foreign distro.
++  return Distro::UnknownDistro;
++
+   Distro::DistroType Version = Distro::UnknownDistro;
+ 
+   // Newer freedesktop.org's compilant systemd-based systems
+diff --git a/lib/Driver/ToolChains/Cuda.cpp b/lib/Driver/ToolChains/Cuda.cpp
+index d14776c5..88bc3ccd 100644
+--- a/lib/Driver/ToolChains/Cuda.cpp
++++ b/lib/Driver/ToolChains/Cuda.cpp
+@@ -119,6 +119,9 @@ CudaInstallationDetector::CudaInstallationDetector(
+     const Driver &D, const llvm::Triple &HostTriple,
+     const llvm::opt::ArgList &Args)
+     : D(D) {
++  // Don't look for CUDA in /usr.
++  return;
++
+   struct Candidate {
+     std::string Path;
+     bool StrictChecking;
+diff --git a/lib/Driver/ToolChains/Linux.cpp b/lib/Driver/ToolChains/Linux.cpp
+--- a/lib/Driver/ToolChains/Linux.cpp
++++ b/lib/Driver/ToolChains/Linux.cpp
+@@ -186,6 +186,10 @@
+ 
+   Generic_GCC::PushPPaths(PPaths);
+ 
++  // Comment out the distro-specific tweaks so that they don't bite when
++  // using Guix on a foreign distro.
++#if 0
++
+   Distro Distro(D.getVFS(), Triple);
+ 
+   if (Distro.IsAlpineLinux() || Triple.isAndroid()) {
+@@ -251,6 +255,7 @@
+ 
+   if (IsAndroid || Distro.IsOpenSUSE())
+     ExtraOpts.push_back("--enable-new-dtags");
++#endif
+ 
+   // The selection of paths to try here is designed to match the patterns which
+   // the GCC driver itself uses, as this is part of the GCC-compatible driver.
+@@ -264,6 +269,7 @@
+ 
+   Generic_GCC::AddMultilibPaths(D, SysRoot, OSLibDir, MultiarchTriple, Paths);
+ 
++#if 0
+   addPathIfExists(D, SysRoot + "/lib/" + MultiarchTriple, Paths);
+   addPathIfExists(D, SysRoot + "/lib/../" + OSLibDir, Paths);
+ 
+@@ -295,9 +301,11 @@
+     addPathIfExists(D, SysRoot + "/" + OSLibDir + "/" + ABIName, Paths);
+     addPathIfExists(D, SysRoot + "/usr/" + OSLibDir + "/" + ABIName, Paths);
+   }
++#endif
+ 
+   Generic_GCC::AddMultiarchPaths(D, SysRoot, OSLibDir, Paths);
+ 
++#if 0
+   // Similar to the logic for GCC above, if we are currently running Clang
+   // inside of the requested system root, add its parent library path to those
+   // searched.
+@@ -305,9 +313,14 @@
+   // directory ('Dir' below) or the ResourceDir.
+   if (StringRef(D.Dir).startswith(SysRoot))
+     addPathIfExists(D, D.Dir + "/../lib", Paths);
++#endif
++
++  // Add libc's lib/ directory to the search path, so that crt1.o, crti.o,
++  // and friends can be found.
++  addPathIfExists(D, "@GLIBC_LIBDIR@", Paths);
+ 
+-  addPathIfExists(D, SysRoot + "/lib", Paths);
+-  addPathIfExists(D, SysRoot + "/usr/lib", Paths);
++  // Add GCC's lib/ directory so libstdc++.so can be found.
++  addPathIfExists(D, GCCInstallation.getParentLibPath(), Paths);
+ }
+ 
+ ToolChain::RuntimeLibType Linux::GetDefaultRuntimeLibType() const {