[WebAssembly] Handle _setjmp and _longjmp in SjLj

[aheejin]

Summary

In some platforms _setjmp and _longjmp are used instead of setjmp
and longjmp. This CL adds support for them.

Fixes https://github.com/emscripten-core/emscripten/issues/14999.

[aheejin]

llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp

838

I wanted to name these variable _SetjmpF of SetjmpF, but clang-tidy didn't like it...

838

Oh, I mean, _SetjmpF of SetjmpF_ (the same for longjmp)

[dschuff]

otherwise LGTM

llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp

841

Is there any way this can happen other than an LLVM bug (e.g. a library problem, or a user's function being used instead of a library function, etc)? If so, it should probably be a fatal error instead of an assert.

[aheejin]

Change to report_fatal_error

llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp

bool WebAssemblyLowerEmscriptenEHSjLj::runOnModule(Module &M) {
   LLVM_DEBUG(dbgs() << "********** Lower Emscripten EH & SjLj **********\n");
 
   LLVMContext &C = M.getContext();
   IRBuilder<> IRB(C);
 
   Function *SetjmpF = M.getFunction("setjmp");
   Function *LongjmpF = M.getFunction("longjmp");
 
+  // In some platforms _setjmp and _longjmp are used instead. Change these to
+  // use setjmp/longjmp instead, because we laster detect these functions by
+  // their names.
+  Function *SetjmpF2 = M.getFunction("_setjmp");
+  Function *LongjmpF2 = M.getFunction("_longjmp");
+  if (SetjmpF2) {
+    if (SetjmpF) {
+      if (SetjmpF->getFunctionType() != SetjmpF2->getFunctionType())
+        report_fatal_error("setjmp and _setjmp have different function types");
+    } else {
+      SetjmpF = Function::Create(SetjmpF2->getFunctionType(),
+                                 GlobalValue::ExternalLinkage, "setjmp", M);
+    }
+    SetjmpF2->replaceAllUsesWith(SetjmpF);
+  }
+  if (LongjmpF2) {
+    if (LongjmpF) {
+      if (LongjmpF->getFunctionType() != LongjmpF2->getFunctionType())
+        report_fatal_error(
+            "longjmp and _longjmp have different function types");
+    } else {
+      LongjmpF = Function::Create(LongjmpF2->getFunctionType(),
+                                  GlobalValue::ExternalLinkage, "setjmp", M);
+    }
+    LongjmpF2->replaceAllUsesWith(LongjmpF);
+  }
+
   auto *TPC = getAnalysisIfAvailable<TargetPassConfig>();
   assert(TPC && "Expected a TargetPassConfig");
   auto &TM = TPC->getTM<WebAssemblyTargetMachine>();
 
   // Declare (or get) global variables __THREW__, __threwValue, and
   // getTempRet0/setTempRet0 function which are used in common for both
   // exception handling and setjmp/longjmp handling
   ThrewGV = getGlobalVariable(M, getAddrIntType(&M), TM, "__THREW__");

llvm/test/CodeGen/WebAssembly/lower-em-sjlj.ll

entry:
 
   ; Pass longjmp as a function argument. This is a call but longjmp is not a
   ; callee but an argument.
   call void @take_longjmp(void (%struct.__jmp_buf_tag*, i32)* @longjmp)
   ; CHECK: call void @take_longjmp(void (%struct.__jmp_buf_tag*, i32)* bitcast (void ([[PTR]], i32)* @emscripten_longjmp to void (%struct.__jmp_buf_tag*, i32)*))
   ret void
 }
 
+; Test if _setjmp and _longjmp calls are treated in the same way as setjmp and
+; longjmp
+define void @_setjmp__longjmp() {
+; CHECK-LABEL: @_setjmp__longjmp
+; These calls should have been transformed away
+; CHECK-NOT: call i32 @_setjmp
+; CHECK-NOT: call void @_longjmp
+entry:
+  %buf = alloca [1 x %struct.__jmp_buf_tag], align 16
+  %arraydecay = getelementptr inbounds [1 x %struct.__jmp_buf_tag], [1 x %struct.__jmp_buf_tag]* %buf, i32 0, i32 0
+  %call = call i32 @_setjmp(%struct.__jmp_buf_tag* %arraydecay) #0
+  %arraydecay1 = getelementptr inbounds [1 x %struct.__jmp_buf_tag], [1 x %struct.__jmp_buf_tag]* %buf, i32 0, i32 0
+  call void @_longjmp(%struct.__jmp_buf_tag* %arraydecay1, i32 1) #1
+  unreachable
+}
+
 ; Function Attrs: nounwind
 declare void @foo() #2
 ; Function Attrs: returns_twice
 declare i32 @setjmp(%struct.__jmp_buf_tag*) #0
+declare i32 @_setjmp(%struct.__jmp_buf_tag*) #0
 ; Function Attrs: noreturn
 declare void @longjmp(%struct.__jmp_buf_tag*, i32) #1
+declare void @_longjmp(%struct.__jmp_buf_tag*, i32) #1
 declare i32 @__gxx_personality_v0(...)
 declare i8* @__cxa_begin_catch(i8*)
 declare void @__cxa_end_catch()
 declare i8* @malloc(i32)
 declare void @free(i8*)
 
 ; JS glue functions and invoke wrappers declaration
 ; CHECK-DAG: declare i32 @getTempRet0()