[WebAssembly] Forbid use of EM_ASM with setjmp/longjmp

Summary:
We tried to support EM_ASM with setjmp/longjmp in binaryen. But with dynamic
linking thrown into the mix, the code is no longer understandable and cannot
be maintained. We also discovered more bugs in the EM_ASM handling code.

To ensure maintainability and correctness of the binaryen code, EM_ASM will
no longer be supported with setjmp/longjmp. This is probably fine since the
support was added recently and haven't be published.

Reviewers: tlively, sbc100, jgravelle-google, kripken

Reviewed By: tlively, kripken

Subscribers: dschuff, hiraditya, aheejin, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66356

llvm-svn: 369137

1 files changed, 24 insertions, 0 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
index 53aede41213..568382bac15 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
@@ -274,6 +274,7 @@ class WebAssemblyLowerEmscriptenEHSjLj final : public ModulePass {
 
   bool areAllExceptionsAllowed() const { return EHWhitelistSet.empty(); }
   bool canLongjmp(Module &M, const Value *Callee) const;
+  bool isEmAsmCall(Module &M, const Value *Callee) const;
 
   void rebuildSSA(Function &F);
 
@@ -537,6 +538,23 @@ bool WebAssemblyLowerEmscriptenEHSjLj::canLongjmp(Module &M,
   return true;
 }
 
+bool WebAssemblyLowerEmscriptenEHSjLj::isEmAsmCall(Module &M,
+                                                   const Value *Callee) const {
+  // This is an exhaustive list from Emscripten's <emscripten/em_asm.h>.
+  Function *EmAsmConstIntF = M.getFunction("emscripten_asm_const_int");
+  Function *EmAsmConstDoubleF = M.getFunction("emscripten_asm_const_double");
+  Function *EmAsmConstIntSyncMainF =
+      M.getFunction("emscripten_asm_const_int_sync_on_main_thread");
+  Function *EmAsmConstDoubleSyncMainF =
+      M.getFunction("emscripten_asm_const_double_sync_on_main_thread");
+  Function *EmAsmConstAsyncMainF =
+      M.getFunction("emscripten_asm_const_async_on_main_thread");
+
+  return Callee == EmAsmConstIntF || Callee == EmAsmConstDoubleF ||
+         Callee == EmAsmConstIntSyncMainF ||
+         Callee == EmAsmConstDoubleSyncMainF || Callee == EmAsmConstAsyncMainF;
+}
+
 // Generate testSetjmp function call seqence with preamble and postamble.
 // The code this generates is equivalent to the following JavaScript code:
 // if (%__THREW__.val != 0 & threwValue != 0) {
@@ -983,6 +1001,12 @@ bool WebAssemblyLowerEmscriptenEHSjLj::runSjLjOnFunction(Function &F) {
       const Value *Callee = CI->getCalledValue();
       if (!canLongjmp(M, Callee))
         continue;
+      if (isEmAsmCall(M, Callee))
+        report_fatal_error("Cannot use EM_ASM* alongside setjmp/longjmp in " +
+                               F.getName() +
+                               ". Please consider using EM_JS, or move the "
+                               "EM_ASM into another function.",
+                           false);
 
       Value *Threw = nullptr;
       BasicBlock *Tail;