[llvm] aca198c - [WebAssembly] Error out when Emscripten SjLj setjmp is used with Wasm EH

[Heejin Ahn via llvm-commits]

Author: Heejin Ahn
Date: 2021-08-12T16:19:04-07:00
New Revision: aca198cf748e32205a835fba2d6d68f95ba1dfdd

URL: https://github.com/llvm/llvm-project/commit/aca198cf748e32205a835fba2d6d68f95ba1dfdd
DIFF: https://github.com/llvm/llvm-project/commit/aca198cf748e32205a835fba2d6d68f95ba1dfdd.diff

LOG: [WebAssembly] Error out when Emscripten SjLj setjmp is used with Wasm EH

Currently, when Wasm EH is used with Emscripten SjLj, Emscripten SjLj
cannot handle `invoke` instructions - it assumes all `invoke`s have been
lowered away with Emscripten EH. But in Wasm EH they are lowered in
instruction selection, so they are still present in the IR stage. This
happens when
1. Wasm EH and Emscripten SjLj are used together
2. A function that calls `setjmp` uses exceptions, i.e., has `invoke`s

We were already erroring out with an assertion failure in this case, but
this CL makes it error out more properly with a valid error message.

Wasm EH + Wasm SjLj will not have this restrictions. (it will have
another restriction though, e.g., `setjmp` cannot be called within
`catch`. But why would anyone do that..)

Reviewed By: dschuff

Differential Revision: https://reviews.llvm.org/D107687

Added: 
    llvm/test/CodeGen/WebAssembly/wasm-eh-em-sjlj-error.ll

Modified: 
    llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
index aac5dd02922d3..ccb6f39e54737 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
@@ -1105,7 +1105,10 @@ bool WebAssemblyLowerEmscriptenEHSjLj::runSjLjOnFunction(Function &F) {
   for (unsigned I = 0; I < BBs.size(); I++) {
     BasicBlock *BB = BBs[I];
     for (Instruction &I : *BB) {
-      assert(!isa<InvokeInst>(&I));
+      if (isa<InvokeInst>(&I))
+        report_fatal_error("When using Wasm EH with Emscripten SjLj, there is "
+                           "a restriction that `setjmp` function call and "
+                           "exception cannot be used within the same function");
       auto *CI = dyn_cast<CallInst>(&I);
       if (!CI)
         continue;

diff  --git a/llvm/test/CodeGen/WebAssembly/wasm-eh-em-sjlj-error.ll b/llvm/test/CodeGen/WebAssembly/wasm-eh-em-sjlj-error.ll
new file mode 100644
index 0000000000000..324a10b327d3b
--- /dev/null
+++ b/llvm/test/CodeGen/WebAssembly/wasm-eh-em-sjlj-error.ll
@@ -0,0 +1,53 @@
+; RUN: not --crash llc < %s -enable-emscripten-sjlj -exception-model=wasm 2>&1 | FileCheck %s
+
+target triple = "wasm32-unknown-unknown"
+
+%struct.__jmp_buf_tag = type { [6 x i32], i32, [32 x i32] }
+
+define void @wasm_eh_emscripten_sjlj_error() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
+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
+  br label %bb
+
+bb:
+  invoke void @foo()
+          to label %try.cont unwind label %catch.dispatch
+
+catch.dispatch:                                   ; preds = %entry
+  %0 = catchswitch within none [label %catch.start] unwind to caller
+
+catch.start:                                      ; preds = %catch.dispatch
+  %1 = catchpad within %0 [i8* null]
+  %2 = call i8* @llvm.wasm.get.exception(token %1)
+  %3 = call i32 @llvm.wasm.get.ehselector(token %1)
+  %4 = call i8* @__cxa_begin_catch(i8* %2) #2 [ "funclet"(token %1) ]
+  call void @__cxa_end_catch() [ "funclet"(token %1) ]
+  catchret from %1 to label %try.cont
+
+try.cont:                                         ; preds = %entry, %catch.start
+  ret void
+}
+
+declare void @foo()
+declare i32 @__gxx_wasm_personality_v0(...)
+; Function Attrs: nounwind
+declare i8* @llvm.wasm.get.exception(token) #0
+; Function Attrs: nounwind
+declare i32 @llvm.wasm.get.ehselector(token) #0
+declare i8* @__cxa_begin_catch(i8*)
+declare void @__cxa_end_catch()
+; Function Attrs: returns_twice
+declare i32 @setjmp(%struct.__jmp_buf_tag*) #0
+; Function Attrs: noreturn
+declare void @longjmp(%struct.__jmp_buf_tag*, i32) #1
+declare i8* @malloc(i32)
+declare void @free(i8*)
+
+attributes #0 = { returns_twice }
+attributes #1 = { noreturn }
+attributes #2 = { nounwind }
+
+; CHECK: LLVM ERROR: When using Wasm EH with Emscripten SjLj, there is a restriction that `setjmp` function call and exception cannot be used within the same function