gnu: chez-scheme-for-racket: Support all systems.

On systems for which Racket's variant of Chez Scheme cannot generate
native code, it can use a 'pbarch' machine type: a variant of the
``portable bytecode'' backend specialized to word size and endianness.
This allows Racket CS to replace Racket BC on those systems while
maintaining comparable performance. (Racket BC lacks JIT support for
those systems anyway.) It also lets us provide a Chez Scheme package on
all systems Guix supports.

This patch adds 'pbarch' support to both 'chez-scheme-for-racket' and
'racket-vm-cs', but it does not change the Racket VM implementation used
for the 'racket' and 'racket-minimal' packages.

* gnu/packages/chez.scm (nix-system->pbarch-machine-type): New variable.
(chez-scheme-for-racket)[inputs]: Use 'libffi' for non-native systems.
[arguments]<#:configure-flags>: Always supply '-m='. Add applicable
flags for non-native systems.
[supported-systems]: Use '%supported-systems'.
[description]: Update.
(chez-scheme-for-racket-bootstrap-bootfiles)[arguments]<#:phases>: Adapt
'build' phase for non-native systems.
* gnu/packages/racket.scm (racket-vm-bc)[description]: Update.
(racket-vm-cs)[description]: Likewise.
[inputs]: Use 'libffi' for non-native systems.
[arguments]<#:configure-flags>: Add applicable flags for non-native
systems.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

2 files changed, 74 insertions, 28 deletions

diff --git a/gnu/packages/chez.scm b/gnu/packages/chez.scm
index 26f653ea9d..5d152b3db5 100644
--- a/gnu/packages/chez.scm
+++ b/gnu/packages/chez.scm
@@ -37,6 +37,7 @@
   #:use-module (gnu packages compression)
   #:use-module (gnu packages ncurses)
   #:use-module (gnu packages ghostscript)
+  #:use-module (gnu packages libffi)
   #:use-module (gnu packages linux)
   #:use-module (gnu packages netpbm)
   #:use-module (gnu packages racket)
@@ -49,6 +50,7 @@
   #:use-module (srfi srfi-26)
   #:export (chez-scheme-for-system
             racket-cs-native-supported-system?
+            nix-system->pbarch-machine-type
             unpack-nanopass+stex))
 
 ;; Commentary:
@@ -231,6 +233,28 @@ future."
     (and=> (assoc-ref %chez-features-table chez-os)
            (cut assoc-ref <> chez-arch))))
 
+(define* (nix-system->pbarch-machine-type #:optional
+                                          (system
+                                           (or (%current-target-system)
+                                               (%current-system)))
+                                          #:key (threads? #t))
+  "Return a string naming the pseudo–machine type used by Racket's variant of
+Chez Scheme to represent the appropriate ``pbarch'' backend for SYSTEM: that
+is, the ``portable bytecode'' backend specialized for SYSTEM's word size and
+endianness.  The result will name the threaded machine type unless THREADS? is
+provided and is #f."
+  (string-append (if threads?
+                     "t"
+                     "")
+                 "pb"
+                 (if (target-64bit? system)
+                     "64"
+                     "32")
+                 ;; missing (guix utils) predicate target-little-endian?
+                 (if (target-ppc32? system)
+                     "b"
+                     "l")))
+
 (define* (racket-cs-native-supported-system? #:optional
                                              (system
                                               (or (%current-target-system)
@@ -449,10 +473,14 @@ and 32-bit PowerPC architectures.")
     ;; When updating, remember to also update %racket-version in racket.scm.
     (source #f) ; avoid problematic cycle with racket.scm
     (inputs
-     (modify-inputs (package-inputs chez-scheme)
-       (delete "libx11" "util-linux:lib")
-        (replace "chez-scheme-bootstrap-bootfiles"
-          chez-scheme-for-racket-bootstrap-bootfiles)))
+     (let ((inputs (modify-inputs (package-inputs chez-scheme)
+                     (replace "chez-scheme-bootstrap-bootfiles"
+                       chez-scheme-for-racket-bootstrap-bootfiles)
+                     (delete "libx11" "util-linux:lib"))))
+       (if (racket-cs-native-supported-system?)
+           inputs
+           (modify-inputs inputs
+             (prepend libffi)))))
     (native-inputs
      (let ((native-inputs (modify-inputs (package-native-inputs chez-scheme)
                             (prepend zuo))))
@@ -473,10 +501,16 @@ and 32-bit PowerPC architectures.")
        ((#:configure-flags cfg-flags #~'())
         #~`("--disable-x11"
             "--threads" ;; ok to potentially duplicate
-            #$@(if (%current-target-system)
-                   (list (string-append "-m="
-                                        (racket-cs-native-supported-system?)))
-                   '())
+            #$(string-append "-m=" (or (racket-cs-native-supported-system?)
+                                       (nix-system->pbarch-machine-type)))
+            ;; ^ could skip -m= for non-cross non-pbarch builds
+            #$@(if (racket-cs-native-supported-system?)
+                   #~()
+                   ;; not inferred on non-native platforms: see
+                   ;; https://racket.discourse.group/t/950/9
+                   #~("--enable-libffi"
+                      "CFLAGS=-g -O2 -D_REENTRANT -pthread"
+                      "LIBS=-lm -ldl -lrt -lffi -lncurses"))
             #$@(if (%current-target-system)
                    (list (string-append "--toolprefix="
                                         (%current-target-system)
@@ -543,10 +577,7 @@ and 32-bit PowerPC architectures.")
               (add-after 'unpack 'chdir
                 (lambda args
                   (chdir "racket/src/ChezScheme"))))))))
-    ;; TODO: How to build pbarch/pbchunks for other systems?
-    ;; See https://racket.discourse.group/t/950
-    (supported-systems (filter racket-cs-native-supported-system?
-                               %supported-systems))
+    (supported-systems %supported-systems)
     (home-page "https://github.com/racket/ChezScheme")
     ;; ^ This is downstream of https://github.com/racket/racket,
     ;; but it's designed to be a friendly landing place for people
@@ -559,13 +590,17 @@ supported by upstream Chez Scheme.
 Main additions to Chez Scheme in the Racket variant:
 @itemize @bullet
 @item
-AArch64 support
+AArch64 code generation
 @item
-Portable bytes (@code{pb}) support, which is mainly useful for bootstrapping
-a build on any supported platform
+Portable bytecode (@code{pb}) mode, which is mainly useful for bootstrapping a
+build on any platform, but can also be used on platforms without native-code
+generation, compiled via Emscripten, linked with @code{libffi}, or used with
+bytecode partially compiled to C
 @item
 Unboxed floating-point arithmetic and flvectors
 @item
+Faster multiplication and division for large exact numbers
+@item
 Type reconstruction during optimization (especially for safe code)
 @item
 Continuation attachments
@@ -576,8 +611,6 @@ accounting
 @item
 Ordered finalization, immobile (but collectable) objects, weak/ephemeron
 generic hash tables, and reference bytevectors
-@item
-Faster multiplication and division for large exact numbers
 @end itemize")
     (license asl2.0)))
 
@@ -655,13 +688,18 @@ source.")))
                          "makefiles/boot.zuo"
                          (search-input-file (or native-inputs inputs)
                                             "/bin/scheme")
-                         #$(racket-cs-native-supported-system?)))
+                         #$(or (racket-cs-native-supported-system?)
+                               (nix-system->pbarch-machine-type))))
                      (else
                       ;; bootstrapping
                       #~(invoke
                          (search-input-file (or native-inputs inputs)
                                             "/opt/racket-vm/bin/racket")
-                         "rktboot/main.rkt"))))))))))
+                         "rktboot/main.rkt"
+                         #$@(if (racket-cs-native-supported-system?)
+                                #~()
+                                (let ((m (nix-system->pbarch-machine-type)))
+                                  #~("--machine" #$m)))))))))))))
     (supported-systems
      (package-supported-systems chez-scheme-for-racket))
     (home-page "https://github.com/racket/ChezScheme")
diff --git a/gnu/packages/racket.scm b/gnu/packages/racket.scm
index 4fcdd2f721..264b44b7fd 100644
--- a/gnu/packages/racket.scm
+++ b/gnu/packages/racket.scm
@@ -311,7 +311,7 @@ One of the early layers implements macros.")
      (version %racket-version)
      (source %racket-origin)
      (inputs (list ncurses ;; <- common to all variants (for #%terminal)
-                   libffi)) ;; <- only for BC variants
+                   libffi)) ;; <- for BC and non-native CS variants
      (native-inputs (cons* zuo ;; <- for all variants
                            libtool ;; <- only for BC variants
                            (if (%current-target-system)
@@ -417,10 +417,8 @@ code to use the 3M garbage collector.")
     (description "The Racket BC (``before Chez'' or ``bytecode'')
 implementation was the default before Racket 8.0.  It uses a compiler written
 in C targeting architecture-independent bytecode, plus a JIT compiler on most
-platforms.  Racket BC has a different C API and supports a slightly different
-set of architectures than the current default runtime system, Racket CS (based
-on ``Chez Scheme'').  It is the recommended implementation for architectures
-that Racket CS doesn't support.
+platforms.  Racket BC has a different C API than the current default runtime
+system, Racket CS (based on ``Chez Scheme'').
 
 This package is the normal implementation of Racket BC with a precise garbage
 collector, 3M (``Moving Memory Manager'').")
@@ -433,9 +431,12 @@ collector, 3M (``Moving Memory Manager'').")
     (inherit racket-vm-bc)
     (name "racket-vm-cs")
     (inputs
-     (modify-inputs (package-inputs racket-vm-cgc)
-       (prepend zlib lz4)
-       (delete "libffi")))
+     (let ((inputs (modify-inputs (package-inputs racket-vm-cgc)
+                     (prepend zlib lz4))))
+       (if (racket-cs-native-supported-system?)
+           (modify-inputs inputs
+             (delete "libffi"))
+           inputs)))
     (native-inputs
      (let ((native-inputs (package-native-inputs racket-vm-cgc)))
        (modify-inputs (if (%current-target-system)
@@ -464,12 +465,19 @@ collector, 3M (``Moving Memory Manager'').")
                                 #+(this-package-native-input
                                    "chez-scheme-for-racket")
                                 "/bin/scheme")
+                 #$@(if (racket-cs-native-supported-system?)
+                        #~()
+                        #~(#$(string-append "--enable-mach="
+                                            (nix-system->pbarch-machine-type))
+                           "--enable-pb"))
                  #$racket-vm-common-configure-flags))))
     (synopsis "Racket CS implementation")
     (description "The Racket CS implementation, which uses ``Chez Scheme'' as
 its core compiler and runtime system, has been the default Racket VM
 implementation since Racket 8.0.  It performs better than the Racket BC
-implementation for most programs.
+implementation for most programs.  On systems for which Racket CS cannot
+generate machine code, this package uses a variant of its ``portable
+bytecode'' backend specialized for word size and endianness.
 
 Using the Racket VM packages directly is not recommended: instead, install the
 @code{racket-minimal} or @code{racket} packages.")