From c03e8e712a79ac2ffe759c97d0908af35c9cac39 Mon Sep 17 00:00:00 2001
From: ivg <ivg@ieee.org>
Date: Fri, 18 Feb 2022 12:34:36 -0500
Subject: [PATCH] selects specific llvm components for linking

Up until now, we were linking all available LLVM components that
resulted in the bloated binary image and linking errors due to
improperly packaged libraries on various distributions, e.g., missing
Polly library, various problems with libterm, and so on, all these
problems arose from components that we do not actually use. Moreover,
the problem were never solved and issues remain open for decades.

The new approach is to link only the selected components. Since the
list of available components is quite extensive (around 200) and there
is no documentation available about their dependencies and intention,
it is quite hard to identify the subset that we really need. The
current default set works fine on llvm-14 but we can refine it later,
once we will discover any problems. The components could be manually
selected via the `./configure` script with the
`--with-llvm-components` option. For example
`--with-llvm-components=all` will enable the old behavior.
---
 oasis/llvm.setup.ml.in | 47 ++++++++++++++++++++++++++++++------------
 1 file changed, 34 insertions(+), 13 deletions(-)

diff --git a/oasis/llvm.setup.ml.in b/oasis/llvm.setup.ml.in
index d0feea53d..cfbe6d3ad 100644
--- a/oasis/llvm.setup.ml.in
+++ b/oasis/llvm.setup.ml.in
@@ -1,3 +1,24 @@
+let default_llvm_components = [
+  "all-targets";
+  "binaryformat";
+  "core";
+  "mc";
+  "debuginfodwarf";
+  "debuginfomsf";
+  "debuginfopdb";
+]
+
+
+let llvm_components () : unit =
+  BaseEnv.var_define
+    ~hide:false
+    ~dump:true
+    ~cli:BaseEnv.CLIWith
+    ~short_desc:(fun () ->
+        "the comma-separated list of required LLVM components")
+    ("llvm_components")
+    (fun () -> String.concat "," default_llvm_components) |>
+  definition_end
 
 let strip_patch ver =
   match String.index_opt ver '.' with
@@ -6,13 +27,15 @@ let strip_patch ver =
 
 let extract config link_static v =
   let link_mode = if link_static then "--link-static" else "" in
-  OASISExec.run_read_one_line ~ctxt config [link_mode; "--"^v]
+  let components = if v = "libs"
+    then String.split_on_char ',' @@ BaseEnv.var_get "llvm_components"
+    else [] in
+  OASISExec.run_read_one_line ~ctxt config @@
+  link_mode :: ("--"^v) :: components
 
-let extract_ldflags config link_static = function
-  | "3.4" -> extract config link_static "ldflags"
-  | _ ->
-    extract config link_static "ldflags" ^
-    " " ^ extract config link_static "system-libs"
+let extract_ldflags config link_static =
+  extract config link_static "ldflags" ^ " " ^
+  extract config link_static "system-libs"
 
 let llvm var () : unit =
   BaseEnv.var_define
@@ -22,12 +45,9 @@ let llvm var () : unit =
     ("llvm_"^var)
     (fun () ->
        let config = BaseEnv.var_get "llvm_config" in
-       let version = strip_patch @@ BaseEnv.var_get "llvm_version" in
-       let link_static = match version with
-         | "3.4" | "3.8" -> false
-         | _ -> BaseEnv.var_get "llvm_static" = "true" in
+       let link_static = BaseEnv.var_get "llvm_static" = "true" in
        if var = "ldflags"
-       then extract_ldflags config link_static version
+       then extract_ldflags config link_static
        else extract config link_static var) |>
   definition_end
 
@@ -36,13 +56,13 @@ let llvm_version () : unit =
     ~hide:false
     ~dump:true
     ~cli:BaseEnv.CLIWith
-    ~short_desc:(fun () -> "llvm version (e.g., 3.4)")
+    ~short_desc:(fun () -> "llvm version (e.g., 10)")
     "llvm_version"
     (fun () ->
        try
          ignore @@ OASISFileUtil.which ~ctxt "llvm-config";
          OASISExec.run_read_one_line ~ctxt "llvm-config" ["--version"]
-       with Not_found -> "3.4") |>
+       with Not_found -> "10") |>
   definition_end
 
 let llvm_config () : unit =
@@ -92,6 +112,7 @@ let llvm_lib () : unit =
 
 let () =
   define [
+    llvm_components;
     llvm_version;
     llvm_config;
     llvm_mainlib;