haskell.compiler.ghc902Binary: bump LLVM by wrapping opt(1) (#440271)

pkgs/development/compilers/ghc/9.0.2-binary.nix

@@ -11,6 +11,7 @@
   numactl,
   libffi,
   llvmPackages,
+  replaceVarsWith,
   coreutils,
   targetPackages,
 
@@ -214,6 +215,20 @@ let
     coreutils # for cat
   ]
   ++ lib.optionals useLLVM [
+    # Allow the use of newer LLVM versions; see the script for details.
+    (replaceVarsWith {
+      name = "subopt";
+      src = ./subopt.bash;
+      dir = "bin";
+      isExecutable = true;
+      preBuild = ''
+        name=opt
+      '';
+      replacements = {
+        inherit (stdenv) shell;
+        opt = lib.getExe' llvmPackages.llvm "opt";
+      };
+    })
     (lib.getBin llvmPackages.llvm)
   ]
   # On darwin, we need unwrapped bintools as well (for otool)

pkgs/development/compilers/ghc/9.2.4-binary.nix

@@ -10,7 +10,6 @@
   libiconv,
   numactl,
   libffi,
-  llvmPackages,
   coreutils,
   targetPackages,
 
@@ -193,8 +192,6 @@ let
       ) binDistUsed.archSpecificLibraries
     )).nixPackage;
 
-  useLLVM = !(import ./common-have-ncg.nix { inherit lib stdenv version; });
-
   libPath = lib.makeLibraryPath (
     # Add arch-specific libraries.
     map ({ nixPackage, ... }: nixPackage) binDistUsed.archSpecificLibraries
@@ -207,9 +204,6 @@ let
     targetPackages.stdenv.cc.bintools
     coreutils # for cat
   ]
-  ++ lib.optionals useLLVM [
-    (lib.getBin llvmPackages.llvm)
-  ]
   # On darwin, we need unwrapped bintools as well (for otool)
   ++ lib.optionals (stdenv.targetPlatform.linker == "cctools") [
     targetPackages.stdenv.cc.bintools.bintools
@@ -217,6 +211,8 @@ let
 
 in
 
+assert import ./common-have-ncg.nix { inherit lib stdenv version; };
+
 stdenv.mkDerivation {
   inherit version;
   pname = "ghc-binary${binDistUsed.variantSuffix}";
@@ -470,7 +466,7 @@ stdenv.mkDerivation {
     targetPrefix = "";
     enableShared = true;
 
-    inherit llvmPackages;
+    llvmPackages = null;
 
     # Our Cabal compiler name
     haskellCompilerName = "ghc-${version}";

pkgs/development/compilers/ghc/9.6.3-binary.nix

@@ -10,7 +10,6 @@
   libiconv,
   numactl,
   libffi,
-  llvmPackages,
   coreutils,
   targetPackages,
 
@@ -192,8 +191,6 @@ let
       ) binDistUsed.archSpecificLibraries
     )).nixPackage;
 
-  useLLVM = !(import ./common-have-ncg.nix { inherit lib stdenv version; });
-
   libPath = lib.makeLibraryPath (
     # Add arch-specific libraries.
     map ({ nixPackage, ... }: nixPackage) binDistUsed.archSpecificLibraries
@@ -206,9 +203,6 @@ let
     targetPackages.stdenv.cc.bintools
     coreutils # for cat
   ]
-  ++ lib.optionals useLLVM [
-    (lib.getBin llvmPackages.llvm)
-  ]
   # On darwin, we need unwrapped bintools as well (for otool)
   ++ lib.optionals (stdenv.targetPlatform.linker == "cctools") [
     targetPackages.stdenv.cc.bintools.bintools
@@ -216,6 +210,8 @@ let
 
 in
 
+assert import ./common-have-ncg.nix { inherit lib stdenv version; };
+
 stdenv.mkDerivation {
   inherit version;
   pname = "ghc-binary${binDistUsed.variantSuffix}";
@@ -449,7 +445,7 @@ stdenv.mkDerivation {
     targetPrefix = "";
     enableShared = true;
 
-    inherit llvmPackages;
+    llvmPackages = null;
 
     # Our Cabal compiler name
     haskellCompilerName = "ghc-${version}";

pkgs/development/compilers/ghc/9.8.4-binary.nix

@@ -9,7 +9,6 @@
   libiconv,
   numactl,
   libffi,
-  llvmPackages,
   coreutils,
   targetPackages,
 
@@ -206,8 +205,6 @@ let
       ) binDistUsed.archSpecificLibraries
     )).nixPackage;
 
-  useLLVM = !(import ./common-have-ncg.nix { inherit lib stdenv version; });
-
   libPath = lib.makeLibraryPath (
     # Add arch-specific libraries.
     map ({ nixPackage, ... }: nixPackage) binDistUsed.archSpecificLibraries
@@ -220,9 +217,6 @@ let
     targetPackages.stdenv.cc.bintools
     coreutils # for cat
   ]
-  ++ lib.optionals useLLVM [
-    (lib.getBin llvmPackages.llvm)
-  ]
   # On darwin, we need unwrapped bintools as well (for otool)
   ++ lib.optionals (stdenv.targetPlatform.linker == "cctools") [
     targetPackages.stdenv.cc.bintools.bintools
@@ -230,6 +224,8 @@ let
 
 in
 
+assert import ./common-have-ncg.nix { inherit lib stdenv version; };
+
 stdenv.mkDerivation {
   inherit version;
   pname = "ghc-binary${binDistUsed.variantSuffix}";
@@ -464,7 +460,7 @@ stdenv.mkDerivation {
     targetPrefix = "";
     enableShared = true;
 
-    inherit llvmPackages;
+    llvmPackages = null;
 
     # Our Cabal compiler name
     haskellCompilerName = "ghc-${version}";

pkgs/development/compilers/ghc/subopt.bash

@@ -0,0 +1,80 @@
+#!@shell@
+
+# This script wraps the LLVM `opt(1)` executable and maps the options
+# passed by old versions of GHC to the equivalents passed by newer
+# versions that support recent versions of LLVM.
+#
+# It achieves the same effect as the following GHC change externally:
+# <https://gitlab.haskell.org/ghc/ghc/-/merge_requests/8999>.
+#
+# This is used solely for bootstrapping newer GHCs from the GHC 9.0.2
+# binary on AArch64, as that is the only architecture supported by that
+# binary distribution that requires LLVM, and our later binary packages
+# all use the native code generator for all supported platforms.
+#
+# No attempt is made to support custom LLVM optimization flags, or the
+# undocumented flag to disable TBAA, or avoid
+# <https://gitlab.haskell.org/ghc/ghc/-/issues/23870>, as these are not
+# required to bootstrap GHC and at worst will produce an error message.
+#
+# It is called `subopt` to reflect the fact that it uses `opt(1)` as a
+# subprocess, and the fact that the GHC build system situation
+# requiring this hack is suboptimal.
+
+set -e
+
+expect() {
+  if [[ $1 != $2 ]]; then
+    printf >&2 'subopt: got %q; expected %q\n' "$1" "$2"
+    return 2
+  fi
+}
+
+if [[ $NIX_DEBUG -ge 1 ]]; then
+  printf >&2 'subopt: before:'
+  printf >&2 ' %q' "$@"
+  printf >&2 '\n'
+fi
+
+args=()
+
+while [[ $# -gt 0 ]]; do
+  case "$1" in
+    -enable-new-pm=0)
+      shift 1
+      ;;
+    -mem2reg)
+      expect "$2" -globalopt
+      expect "$3" -lower-expect
+      expect "$4" -enable-tbaa
+      expect "$5" -tbaa
+      args+=('-passes=function(require<tbaa>),function(mem2reg),globalopt,function(lower-expect)')
+      shift 5
+      ;;
+    -O1)
+      expect "$2" -globalopt
+      expect "$3" -enable-tbaa
+      expect "$4" -tbaa
+      args+=('-passes=default<O1>')
+      shift 4
+      ;;
+    -O2)
+      expect "$2" -enable-tbaa
+      expect "$3" -tbaa
+      args+=('-passes=default<O2>')
+      shift 3
+      ;;
+    *)
+      args+=("$1")
+      shift 1
+      ;;
+  esac
+done
+
+if [[ $NIX_DEBUG -ge 1 ]]; then
+  printf >&2 'subopt: after:'
+  printf >&2 ' %q' "${args[@]}"
+  printf >&2 '\n'
+fi
+
+exec @opt@ "${args[@]}"

pkgs/top-level/haskell-packages.nix

@@ -70,21 +70,16 @@ in
       bb = pkgsBuildBuild.haskell;
     in
     {
+      # Required to bootstrap 9.4.8.
       ghc902Binary = callPackage ../development/compilers/ghc/9.0.2-binary.nix {
-        llvmPackages = pkgs.llvmPackages_12;
+        llvmPackages = pkgs.llvmPackages_20;
       };
 
-      ghc924Binary = callPackage ../development/compilers/ghc/9.2.4-binary.nix {
-        llvmPackages = pkgs.llvmPackages_12;
-      };
+      ghc924Binary = callPackage ../development/compilers/ghc/9.2.4-binary.nix { };
 
-      ghc963Binary = callPackage ../development/compilers/ghc/9.6.3-binary.nix {
-        llvmPackages = pkgs.llvmPackages_15;
-      };
+      ghc963Binary = callPackage ../development/compilers/ghc/9.6.3-binary.nix { };
 
-      ghc984Binary = callPackage ../development/compilers/ghc/9.8.4-binary.nix {
-        llvmPackages = pkgs.llvmPackages_15;
-      };
+      ghc984Binary = callPackage ../development/compilers/ghc/9.8.4-binary.nix { };
 
       ghc948 = callPackage ../development/compilers/ghc/9.4.8.nix {
         bootPkgs =