Add gen-dll as replacement for dll-split

Summary:
This tool can be used to generate dll's for any list of object files
given to it. It will then repartition them automatically to fit within
a dll and generates as many dll's as needed to do this. Cyclic dependencies
between these generated dlls are handle automatically so there is no need
to tell it how to partition.

It is also a lot more general than `dll-split` as it is able to split any
package not just `libGHC`. It also uses a trick using GNU style import libraries
to hide the splitting from the rest of the pipeline. Which means come linking time
you don't need to know which dll contains what symbol or how many split dlls were
created.

The import libraries are by default created with libtool. However since libtool is BFD
based it is very slow. So if present and detected by configure the `genlib` tool
from the msys2 project is used. This makes a difference of about ~45 minutes when compiling.

To install `genlib` run `pacman -Sy mingw-w64-$(uname -m)-tools-git`.

More detailed explaination of the process can be found here
https://ghc.haskell.org/trac/ghc/wiki/WindowsDynamicLinking

Test Plan: ./validate

Reviewers: austin, hvr, bgamari, erikd, simonmar

Reviewed By: bgamari

Subscribers: snowleopard, rwbarton, thomie, erikd, #ghc_windows_task_force

GHC Trac Issues: #5987

Differential Revision: https://phabricator.haskell.org/D3883

1 files changed, 31 insertions, 16 deletions

diff --git a/configure.ac b/configure.ac
index dd721447c4..500be7e491 100644
--- a/configure.ac
+++ b/configure.ac
@@ -391,6 +391,8 @@ then
     OBJDUMP="${mingwbin}objdump.exe"
     fp_prog_ar="${mingwbin}ar.exe"
 
+    AC_PATH_PROG([Genlib],[genlib])
+
     # NB. Download the perl binaries if required
     if ! test -d inplace/perl ||
          test inplace/perl -ot ghc-tarballs/perl/ghc-perl*.tar.gz
@@ -420,13 +422,25 @@ then
     AC_PATH_PROG([OBJDUMP],[objdump])
     AC_PATH_PROG([DllWrap],[dllwrap])
     AC_PATH_PROG([Windres],[windres])
+    AC_PATH_PROG([Genlib],[genlib])
 fi
 
 DllWrapCmd="$DllWrap"
 WindresCmd="$Windres"
 
+HAVE_GENLIB=False
+if test "$HostOS" = "mingw32"
+then
+    if test "$Genlib" != ""; then
+        GenlibCmd="$(cygpath -m $Genlib)"
+        HAVE_GENLIB=True
+    fi
+fi
+
 AC_SUBST([DllWrapCmd])
 AC_SUBST([WindresCmd])
+AC_SUBST([GenlibCmd])
+AC_SUBST([HAVE_GENLIB])
 
 FP_ICONV
 FP_GMP
@@ -587,18 +601,6 @@ esac
 ObjdumpCmd="$OBJDUMP"
 AC_SUBST([ObjdumpCmd])
 
-dnl ** Which ar to use?
-dnl --------------------------------------------------------------
-if test "$HostOS" != "mingw32"; then
-    AC_CHECK_TARGET_TOOL([AR], [ar])
-    if test "$AR" = ":"; then
-        AC_MSG_ERROR([cannot find ar in your PATH])
-    fi
-fi
-ArCmd="$AR"
-fp_prog_ar="$AR"
-AC_SUBST([ArCmd])
-
 dnl ** Which ranlib to use?
 dnl --------------------------------------------------------------
 AC_PROG_RANLIB
@@ -610,9 +612,21 @@ RANLIB="$RanlibCmd"
 
 dnl ** which libtool to use?
 dnl --------------------------------------------------------------
-AC_CHECK_TARGET_TOOL([LIBTOOL], [libtool])
-LibtoolCmd="$LIBTOOL"
-LIBTOOL="$LibtoolCmd"
+# The host normalization on Windows breaks autoconf, it no longer
+# thinks that target == host so it never checks the unqualified
+# tools for Windows. I don't know why we do this whole normalization thing
+# as it just breaks everything.. but for now, just check the unqualified one
+# if on Windows.
+if test "$HostOS" = "mingw32"
+then
+    AC_PATH_PROG([LIBTOOL],[libtool])
+    LibtoolCmd="$(cygpath -m $LIBTOOL)"
+else
+    AC_CHECK_TARGET_TOOL([LIBTOOL], [libtool])
+    LibtoolCmd="$LIBTOOL"
+    LIBTOOL="$LibtoolCmd"
+fi
+AC_SUBST([LibtoolCmd])
 
 # Here is where we re-target which specific version of the LLVM
 # tools we are looking for. In the past, GHC supported a number of
@@ -1249,7 +1263,7 @@ checkMake380() {
 checkMake380 make
 checkMake380 gmake
 
-AC_CONFIG_FILES([mk/config.mk mk/install.mk mk/project.mk compiler/ghc.cabal ghc/ghc-bin.cabal utils/runghc/runghc.cabal libraries/ghc-boot/ghc-boot.cabal libraries/ghc-boot-th/ghc-boot-th.cabal libraries/ghci/ghci.cabal settings docs/users_guide/ghc_config.py docs/index.html libraries/prologue.txt distrib/configure.ac])
+AC_CONFIG_FILES([mk/config.mk mk/install.mk mk/project.mk compiler/ghc.cabal ghc/ghc-bin.cabal utils/runghc/runghc.cabal utils/gen-dll/gen-dll.cabal libraries/ghc-boot/ghc-boot.cabal libraries/ghc-boot-th/ghc-boot-th.cabal libraries/ghci/ghci.cabal settings docs/users_guide/ghc_config.py docs/index.html libraries/prologue.txt distrib/configure.ac])
 AC_OUTPUT
 [
 if test "$print_make_warning" = "true"; then
@@ -1302,6 +1316,7 @@ echo "\
    ranlib       : $RanlibCmd
    windres      : $WindresCmd
    dllwrap      : $DllWrapCmd
+   genlib       : $GenlibCmd
    Happy        : $HappyCmd ($HappyVersion)
    Alex         : $AlexCmd ($AlexVersion)
    Perl         : $PerlCmd