Consolidate `TablesNextToCode` and `GhcUnreigsterised` in configure (#15548)

`TablesNextToCode` is now a substituted by configure, where it has the
correct defaults and error handling. Nowhere else needs to duplicate
that, though we may want the compiler to to guard against bogus settings
files.

I renamed it from `GhcEnableTablesNextToCode` to `TablesNextToCode` to:

 - Help me guard against any unfixed usages

 - Remove any lingering connotation that this flag needs to be combined
   with `GhcUnreigsterised`.

Original reviewers:

Original subscribers: TerrorJack, rwbarton, carter

Original Differential Revision: https://phabricator.haskell.org/D5082

1 files changed, 50 insertions, 6 deletions

diff --git a/configure.ac b/configure.ac
index aa48872b4e..0524d140b2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -271,6 +271,55 @@ AC_ARG_ENABLE(unregisterised,
 )
 AC_SUBST(Unregisterised)
 
+dnl ** Do a build with tables next to code?
+dnl
+dnl Whether the target architecture supports placing info tables
+dnl directly before the entry code (see TABLES_NEXT_TO_CODE in the RTS).
+dnl Whether we actually compile for TABLES_NEXT_TO_CODE depends on
+dnl whether we're building unregisterised code or not, which may be
+dnl decided by options to the compiler later.
+dnl
+dnl See https://gitlab.haskell.org/ghc/ghc/wikis/commentary/rts/storage/heap-objects#tables_next_to_code
+dnl --------------------------------------------------------------
+case "$Unregisterised" in
+    NO)
+        case "$TargetArch" in
+            ia64|powerpc64|powerpc64le)
+                TablesNextToCodeDefault=NO
+                ;;
+            *)
+                TablesNextToCodeDefault=YES
+                ;;
+        esac
+        ;;
+    YES)
+        TablesNextToCodeDefault=NO
+        ;;
+esac
+AC_ARG_ENABLE(tables-next-to-code,
+[AC_HELP_STRING([--enable-tables-next-to-code],
+[Build an tables-next-to-code compiler (enabled by default on platforms without registerised support) [default="$TablesNextToCodeDefault"]])],
+[ if test x"$enableval" = x"yes"; then
+        TablesNextToCode=YES
+  else
+        TablesNextToCode=NO
+  fi
+],
+[TablesNextToCode="$TablesNextToCodeDefault"]
+)
+
+fail() {
+    echo >&2
+    echo "$1" >&2
+    exit 1
+}
+
+if test "$TablesNextToCodeDefault" = "NO" && test "$TablesNextToCode" = "YES"; then
+    fail "Error: tables next to code was requested but is not supported"
+fi
+
+AC_SUBST(TablesNextToCode)
+
 dnl ** Does target have runtime linker support?
 dnl --------------------------------------------------------------
 case "$target" in
@@ -286,12 +335,6 @@ AC_SUBST(HaskellHaveRTSLinker)
 # Requires FPTOOLS_SET_PLATFORM_VARS to be run first.
 FP_FIND_ROOT
 
-fail() {
-    echo >&2
-    echo "$1" >&2
-    exit 1
-}
-
 
 if test "$HostOS" = "mingw32"
 then
@@ -1335,6 +1378,7 @@ echo "\
       which is version       : $GccVersion
    Building a cross compiler : $CrossCompiling
    Unregisterised            : $Unregisterised
+   TablesNextToCode          : $TablesNextToCode
    hs-cpp       : $HaskellCPPCmd
    hs-cpp-flags : $HaskellCPPArgs
    ar           : $ArCmd