From 5e92a4f1864c49867906624f1b16b14c57ee357a Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
Date: Fri, 16 Oct 2020 01:42:56 -0500
Subject: finalize: add --mutable-sp flag (#3250)

This flag disables the features of `wasm-emscripten-finalize`
the replace the mutable global import of `__stack_pointer`.

See the corresponding emscripten change that depends on this
one: https://github.com/emscripten-core/emscripten/pull/12536
---
 src/tools/wasm-emscripten-finalize.cpp | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

(limited to 'src')

diff --git a/src/tools/wasm-emscripten-finalize.cpp b/src/tools/wasm-emscripten-finalize.cpp
index a2322a8f3..172ce08ce 100644
--- a/src/tools/wasm-emscripten-finalize.cpp
+++ b/src/tools/wasm-emscripten-finalize.cpp
@@ -52,6 +52,7 @@ int main(int argc, const char* argv[]) {
   bool DWARF = false;
   bool sideModule = false;
   bool legacyPIC = true;
+  bool mutableSP = false;
   bool legalizeJavaScriptFFI = true;
   bool bigInt = false;
   bool checkStackOverflow = false;
@@ -110,6 +111,13 @@ int main(int argc, const char* argv[]) {
          [&sideModule](Options* o, const std::string& argument) {
            sideModule = true;
          })
+    .add("--mutable-sp",
+         "",
+         "Allow the import of __stack_pointer as a mutable global",
+         Options::Arguments::Zero,
+         [&mutableSP](Options* o, const std::string& argument) {
+           mutableSP = true;
+         })
     .add("--new-pic-abi",
          "",
          "Use new/llvm PIC abi",
@@ -278,7 +286,7 @@ int main(int argc, const char* argv[]) {
   passRunner.setDebug(options.debug);
   passRunner.setDebugInfo(debugInfo);
 
-  if (checkStackOverflow && !sideModule) {
+  if (checkStackOverflow) {
     if (!standaloneWasm) {
       // In standalone mode we don't set a handler at all.. which means
       // just trap on overflow.
@@ -288,7 +296,7 @@ int main(int argc, const char* argv[]) {
     passRunner.add("stack-check");
   }
 
-  if (sideModule) {
+  if (sideModule && !mutableSP) {
     passRunner.add("replace-stack-pointer");
   }
 
@@ -333,7 +341,9 @@ int main(int argc, const char* argv[]) {
   } else {
     BYN_TRACE("finalizing as regular module\n");
     if (legacyPIC) {
-      generator.internalizeStackPointerGlobal();
+      if (!mutableSP) {
+        generator.internalizeStackPointerGlobal();
+      }
       // For side modules these gets called via __post_instantiate
       if (Function* F = wasm.getFunctionOrNull(ASSIGN_GOT_ENTRIES)) {
         auto* ex = new Export();
-- 
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