Drop libffi; Stop shipping a copy of libffi

GHC used to depend on an in-flight version of libffi. As libffis releases are more
frequent now, there is no immediate need for this anymore. GHC should be able
to rely on system provided libffi, and not try to become a system library package
manager as well.

Author: angerman

.gitmodules

@@ -100,10 +100,6 @@
 	path = utils/hsc2hs
 	url = https://gitlab.haskell.org/ghc/hsc2hs.git
 	ignore = untracked
-[submodule "libffi-tarballs"]
-	path = libffi-tarballs
-	url = https://gitlab.haskell.org/ghc/libffi-tarballs.git
-	ignore = untracked
 [submodule "gmp-tarballs"]
 	path = libraries/ghc-internal/gmp/gmp-tarballs
 	url = https://gitlab.haskell.org/ghc/gmp-tarballs.git

compiler/GHC/Driver/CodeOutput.hs

@@ -255,12 +255,11 @@ outputJS _ _ _ _ _ = pgmError $ "codeOutput: Hit JavaScript case. We should neve
 -}
 
 {-
-Note [Packaging libffi headers]
+Note [libffi headers]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 The C code emitted by GHC for libffi adjustors must depend upon the ffi_arg type,
-defined in <ffi.h>. For this reason, we must ensure that <ffi.h> is available
-in binary distributions. To do so, we install these headers as part of the
-`rts` package.
+defined in <ffi.h>. On systems where GHC uses the libffi adjustors, the libffi
+library, and headers must be installed.
 -}
 
 outputForeignStubs

libffi-tarballs

@@ -37,7 +37,6 @@
 # localpath                  tag         remotepath                      upstreamurl
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 ghc-tarballs                 windows     ghc-tarballs.git                -
-libffi-tarballs              -           -                               -
 utils/hsc2hs                 -           -                               ssh://[email protected]/haskell/hsc2hs.git
 libraries/array              -           -                               -
 libraries/binary             -           -                               https://github.com/kolmodin/binary.git

packages

@@ -276,9 +276,6 @@ flag librt
 flag libdl
   default: False
   manual: True
-flag use-system-libffi
-  default: False
-  manual: True
 flag libffi-adjustors
   default: False
   manual: True
@@ -402,18 +399,6 @@ library
                         stg/Types.h
 
     else
-      -- If we are using an in-tree libffi then we must declare it as a bundled
-      -- library to ensure that Cabal installs it.
-      if !flag(use-system-libffi)
-        if os(windows)
-          extra-bundled-libraries: Cffi-6
-        else
-          extra-bundled-libraries: Cffi
-
-        install-includes: ffi.h ffitarget.h
-        -- ^ see Note [Packaging libffi headers] in
-        -- GHC.Driver.CodeOutput.
-
       -- Here we declare several flavours to be available when passing the
       -- suitable (combination of) flag(s) when configuring the RTS from hadrian,
       -- using Cabal.
@@ -465,9 +450,6 @@ library
          extra-libraries: rt
       if flag(libdl)
          extra-libraries: dl
-      if flag(use-system-libffi)
-         extra-libraries: ffi
-         extra-libraries-static: ffi
       if os(windows)
          extra-libraries:
             -- for the linker
@@ -634,6 +616,8 @@ library
       -- Adjustor stuff
       if flag(libffi-adjustors)
         c-sources: adjustor/LibffiAdjustor.c
+        extra-libraries: ffi
+        extra-libraries-static: ffi
       else
         -- Use GHC's native adjustors
         if arch(i386)
@@ -646,6 +630,11 @@ library
           else
             asm-sources: adjustor/NativeAmd64Asm.S
             c-sources: adjustor/NativeAmd64.c
+        -- fall back to the LibffiAdjustor if neither i386, or x86_64
+        if !arch(x86_64) && !arch(i386)
+          c-sources: adjustor/LibffiAdjustor.c
+          extra-libraries: ffi
+          extra-libraries-static: ffi
 
       -- Use assembler STG entrypoint on architectures where it is used
       if arch(ppc) || arch(ppc64) || arch(s390x) || arch(riscv64) || arch(loongarch64)