bintoolsDualAs: Add package

For reasons explained in the commit contents, in order to build the
native gnat package for x86_64-darwin, the native gnatboot package for
x86_64-darwin must have access to both the Clang integrated assembler
and the cctools GNU assembler for that platform.  This commit creates a
package with both of those assemblers that x86_64-darwin gnatboot can
then be wrapped with.

1 files changed, 27 insertions, 3 deletions

diff --git a/pkgs/os-specific/darwin/binutils/default.nix b/pkgs/os-specific/darwin/binutils/default.nix
index c5bc50cafd7..3b1a2636873 100644
--- a/pkgs/os-specific/darwin/binutils/default.nix
+++ b/pkgs/os-specific/darwin/binutils/default.nix
@@ -1,4 +1,4 @@
-{ lib, stdenv, makeWrapper, binutils-unwrapped, cctools, llvm, clang-unwrapped }:
+{ lib, stdenv, makeWrapper, binutils-unwrapped, cctools, llvm, clang-unwrapped, dualAs ? false }:
 
 # Make sure both underlying packages claim to have prepended their binaries
 # with the same targetPrefix.
@@ -15,7 +15,7 @@ in
 
 # TODO: loop over targetPrefixed binaries too
 stdenv.mkDerivation {
-  pname = "${targetPrefix}cctools-binutils-darwin";
+  pname = "${targetPrefix}cctools-binutils-darwin" + lib.optionalString dualAs "-dualas";
   inherit (cctools) version;
   outputs = [ "out" "man" ];
   buildCommand = ''
@@ -59,9 +59,33 @@ stdenv.mkDerivation {
     rm $out/bin/${targetPrefix}as
     makeWrapper "${clang-unwrapped}/bin/clang" "$out/bin/${targetPrefix}as" \
       --add-flags "-x assembler -integrated-as -c"
+  ''
+  # x86-64 Darwin gnatboot emits assembly
+  # with MOVQ as the mnemonic for quadword interunit moves
+  # such as `movq %rbp, %xmm0`.
+  # The clang integrated assembler recognises this as valid,
+  # but unfortunately the cctools-port GNU assembler does not;
+  # it instead uses MOVD as the mnemonic.
+  # The assembly that a GCC build emits is determined at build time
+  # and cannot be changed afterwards.
+  #
+  # To build GNAT on x86-64 Darwin, therefore,
+  # we need both the clang _and_ the cctools-port assemblers to be available:
+  # the former to build at least the stage1 compiler,
+  # and the latter at least to be detectable
+  # as the target for the final compiler.
+  #
+  # We choose to match the Aarch64 case above,
+  # wrapping the clang integrated assembler as `as`.
+  # It then seems sensible to wrap the cctools GNU assembler as `gas`.
+  #
+  + lib.optionalString (stdenv.isx86_64 && dualAs) ''
+    mv $out/bin/${targetPrefix}as $out/bin/${targetPrefix}gas
+    makeWrapper "${clang-unwrapped}/bin/clang" "$out/bin/${targetPrefix}as" \
+      --add-flags "-x assembler -integrated-as -c"
   '';
 
-  nativeBuildInputs = lib.optionals stdenv.isAarch64 [ makeWrapper ];
+  nativeBuildInputs = lib.optionals (stdenv.isAarch64 || dualAs) [ makeWrapper ];
 
   passthru = {
     inherit targetPrefix;