From 9745fcfbffb6434bacdec69082739c9e0229c6f2 Mon Sep 17 00:00:00 2001
From: Cheng Shao <terrorjack@type.dance>
Date: Tue, 1 Oct 2024 19:09:26 +0000
Subject: [PATCH] driver: add necessary link-time flags for wasm shared libs
This commit adds necessary link-time flags for wasm shared libs, see
added comments for detailed explanation.
---
compiler/GHC/Linker/Dynamic.hs | 33 +++++++++++++++++++++++++++++++--
1 file changed, 31 insertions(+), 2 deletions(-)
diff --git a/compiler/GHC/Linker/Dynamic.hs b/compiler/GHC/Linker/Dynamic.hs
index 58f7a75f4d6..b8aedd90acf 100644
--- a/compiler/GHC/Linker/Dynamic.hs
+++ b/compiler/GHC/Linker/Dynamic.hs
@@ -32,6 +32,7 @@ linkDynLib :: Logger -> TmpFs -> DynFlags -> UnitEnv -> [String] -> [UnitId] ->
linkDynLib logger tmpfs dflags0 unit_env o_files dep_packages
= do
let platform = ue_platform unit_env
+ arch = platformArch platform
os = platformOS platform
-- This is a rather ugly hack to fix dynamically linked
@@ -80,8 +81,13 @@ linkDynLib logger tmpfs dflags0 unit_env o_files dep_packages
--
-- * if -flink-rts is used, we link with the rts.
--
+ -- * on wasm we need to ensure libHSrts*.so is listed in
+ -- WASM_DYLINK_NEEDED, otherwise dyld can't load it.
+ --
+ --
let pkgs_without_rts = filter ((/= rtsUnitId) . unitId) pkgs_with_rts
pkgs
+ | ArchWasm32 <- arch = pkgs_with_rts
| OSMinGW32 <- os = pkgs_with_rts
| gopt Opt_LinkRts dflags = pkgs_with_rts
| otherwise = pkgs_without_rts
@@ -219,7 +225,8 @@ linkDynLib logger tmpfs dflags0 unit_env o_files dep_packages
-- non-PIC intra-package-relocations for
-- performance (where symbolic linking works)
-- See Note [-Bsymbolic assumptions by GHC]
- ["-Wl,-Bsymbolic" | not unregisterised]
+ -- wasm-ld accepts --Bsymbolic instead
+ ["-Wl,-Bsymbolic" | not unregisterised && arch /= ArchWasm32 ]
runLink logger tmpfs linker_config (
map Option verbFlags
@@ -232,7 +239,29 @@ linkDynLib logger tmpfs dflags0 unit_env o_files dep_packages
++ map Option bsymbolicFlag
-- Set the library soname. We use -h rather than -soname as
-- Solaris 10 doesn't support the latter:
- ++ [ Option ("-Wl,-h," ++ takeFileName output_fn) ]
+ -- wasm-ld only accepts -soname and it's of little use anyway
+ ++ [ Option ("-Wl,-h," ++ takeFileName output_fn) | arch /= ArchWasm32 ]
+ -- 1. On wasm, --Bsymbolic is an optimization, not
+ -- a requirement. We build the wasi-sdk sysroot
+ -- shared libs as well as all Haskell shared
+ -- libs with --Bsymbolic, but dyld can handle
+ -- shared libs without --Bsymbolic at
+ -- link-time. Though there will be more
+ -- imports/exports to slow things down.
+ -- 2. --experimental-pic silences wasm-ld warnings
+ -- that PIC is experimental.
+ -- 3. --unresolved-symbols=import-dynamic turns
+ -- unresolved symbols to GOT.mem/GOT.func/env
+ -- imports, which can be gracefully handled by
+ -- dyld as lazy bindings. Ideally we'd only
+ -- enable this for rts since it forward
+ -- references ghc-prim/ghc-internal, but too
+ -- many Haskell packages would be rejected at
+ -- link-time even if their code refers to
+ -- something that will not be called at
+ -- run-time in wasm, so enabling it in the
+ -- driver is a more pragmatic solution.
+ ++ [ Option "-Wl,--Bsymbolic,--experimental-pic,--unresolved-symbols=import-dynamic" | arch == ArchWasm32 ]
++ extra_ld_inputs
++ map Option lib_path_opts
++ map Option pkg_lib_path_opts
--
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