Revert "[clang][WebAssembly] Support wasm32-wasi shared libraries"

This reverts commit a7d11c4.

We just want to update the beta branch with the necessary fixes.
This branch rustc/16.0-2023-06-05 has completed its mission on the
master branch.
So we can revert this commit for beta updates.

Author: dianqk

clang/docs/ReleaseNotes.rst

@@ -1103,12 +1103,6 @@ WebAssembly Support
 ^^^^^^^^^^^^^^^^^^^
 - The -mcpu=generic configuration now enables sign-ext and mutable-globals. These
   proposals are standardized and available in all major engines.
-- Shared library support (and PIC code generation) for WebAssembly is no longer
-  limited to the Emscripten target OS and now works with other targets such as
-  wasm32-wasi.  Note that the `format
-  <https://github.com/WebAssembly/tool-conventions/blob/main/DynamicLinking.md>`_
-  is not yet stable and may change between LLVM versions.  Also, WASI does not
-  yet have facilities to load dynamic libraries.
 
 DWARF Support in Clang
 ----------------------

clang/lib/Driver/ToolChains/WebAssembly.cpp

@@ -101,16 +101,13 @@ void wasm::Linker::ConstructJob(Compilation &C, const JobAction &JA,
           << CM << A->getOption().getName();
     }
   }
-  if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles, options::OPT_shared))
+  if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles))
     CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath(Crt1)));
   if (Entry) {
     CmdArgs.push_back(Args.MakeArgString("--entry"));
     CmdArgs.push_back(Args.MakeArgString(Entry));
   }
 
-  if (Args.hasArg(options::OPT_shared))
-    CmdArgs.push_back(Args.MakeArgString("-shared"));
-
   AddLinkerInputs(ToolChain, Inputs, Args, CmdArgs, JA);
 
   if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {

clang/test/Driver/wasm-toolchain.c

@@ -33,20 +33,6 @@
 // LINK_KNOWN: "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
 // LINK_KNOWN: wasm-ld{{.*}}" "-L/foo/lib/wasm32-wasi" "crt1.o" "[[temp]]" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-o" "a.out"
 
-// -shared should be passed through to `wasm-ld` and not include crt1.o with a known OS.
-
-// RUN: %clang -### -shared --target=wasm32-wasi --sysroot=/foo %s 2>&1 \
-// RUN:   | FileCheck -check-prefix=LINK_KNOWN_SHARED %s
-// LINK_KNOWN_SHARED: "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
-// LINK_KNOWN_SHARED: wasm-ld{{.*}}" "-L/foo/lib/wasm32-wasi" "-shared" "[[temp]]" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-o" "a.out"
-
-// -shared should be passed through to `wasm-ld` and not include crt1.o with an unknown OS.
-
-// RUN: %clang -### -shared --target=wasm32-unknown-unknown --sysroot=/foo %s 2>&1 \
-// RUN:   | FileCheck -check-prefix=LINK_UNKNOWN_SHARED %s
-// LINK_UNKNOWN_SHARED: "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
-// LINK_UNKNOWN_SHARED: wasm-ld{{.*}}" "-shared" "[[temp]]" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-o" "a.out"
-
 // A basic C link command-line with optimization with known OS.
 
 // RUN: %clang -### -O2 --target=wasm32-wasi --sysroot=/foo %s 2>&1 \
@@ -60,18 +46,6 @@
 // RUN:   | FileCheck -check-prefix=COMPILE %s
 // COMPILE: "-cc1" {{.*}} "-internal-isystem" "/foo/include/wasm32-wasi" "-internal-isystem" "/foo/include"
 
-// -fPIC should work on a known OS
-
-// RUN: %clang -### -fPIC --target=wasm32-wasi --sysroot=/foo %s 2>&1 \
-// RUN:   | FileCheck -check-prefix=COMPILE_KNOWN_PIC %s
-// COMPILE_KNOWN_PIC: "-cc1" {{.*}} "-mrelocation-model" "pic" "-pic-level" "2" {{.*}} "-internal-isystem" "/foo/include/wasm32-wasi" "-internal-isystem" "/foo/include"
-
-// -fPIC should work on an unknown OS
-
-// RUN: %clang -### -fPIC --target=wasm32-unknown-unknown --sysroot=/foo %s 2>&1 \
-// RUN:   | FileCheck -check-prefix=COMPILE_UNKNOWN_PIC %s
-// COMPILE_UNKNOWN_PIC: "-cc1" {{.*}} "-mrelocation-model" "pic" "-pic-level" "2"
-
 // Thread-related command line tests.
 
 // '-pthread' sets +atomics, +bulk-memory, +mutable-globals, +sign-ext, and --shared-memory

llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp

@@ -98,6 +98,13 @@ static Reloc::Model getEffectiveRelocModel(std::optional<Reloc::Model> RM,
     return Reloc::Static;
   }
 
+  if (!TT.isOSEmscripten()) {
+    // Relocation modes other than static are currently implemented in a way
+    // that only works for Emscripten, so disable them if we aren't targeting
+    // Emscripten.
+    return Reloc::Static;
+  }
+
   return *RM;
 }