[PATCH] D117943: [WebAssembly] Treat __cxa_end_catch not longjmpable in Emscripten SjLj

[Heejin Ahn via Phabricator via llvm-commits]

aheejin created this revision.
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In D117610 <https://reviews.llvm.org/D117610> we maded `__cxa_end_catch` longjmpable even though it was not
to make unwind destination relationships correct. But we only need to do
this in Wasm SjLj, and doing this in Emscripten SjLj does not make the
code incorrect but add unnecessary invokes. This CL treats
`__cxa_end_catch` longjmpable only in Wasm SjLj.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D117943

Files:
  llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
  llvm/test/CodeGen/WebAssembly/lower-em-ehsjlj.ll


Index: llvm/test/CodeGen/WebAssembly/lower-em-ehsjlj.ll
===================================================================
--- llvm/test/CodeGen/WebAssembly/lower-em-ehsjlj.ll
+++ llvm/test/CodeGen/WebAssembly/lower-em-ehsjlj.ll
@@ -33,21 +33,23 @@
 ; CHECK-NEXT: %[[CMP:.*]] = icmp eq i32 %__THREW__.val, 1
 ; CHECK-NEXT: br i1 %[[CMP]], label %lpad, label %try.cont
 
-; longjmp checking part
-; CHECK:    if.then1:
-; CHECK:      call i32 @testSetjmp
-
+; CHECK:    lpad:
 lpad:                                             ; preds = %entry
   %0 = landingpad { i8*, i32 }
           catch i8* null
   %1 = extractvalue { i8*, i32 } %0, 0
   %2 = extractvalue { i8*, i32 } %0, 1
+; CHECK-NOT:  call {{.*}} void @__invoke_void(void ()* @__cxa_end_catch)
   %3 = call i8* @__cxa_begin_catch(i8* %1) #2
   call void @__cxa_end_catch()
   br label %try.cont
 
 try.cont:                                         ; preds = %lpad, %entry
   ret void
+
+; longjmp checking part
+; CHECK:    if.then1:
+; CHECK:      call i32 @testSetjmp
 }
 
 ; @foo can either throw an exception or longjmp. Because this function doesn't
Index: llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
===================================================================
--- llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
+++ llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
@@ -630,9 +630,9 @@
 
   // Exception-catching related functions
   //
-  // We intentionally excluded __cxa_end_catch here even though it surely cannot
-  // longjmp, in order to maintain the unwind relationship from all existing
-  // catchpads (and calls within them) to catch.dispatch.longjmp.
+  // We intentionally treat __cxa_end_catch longjmpable in Wasm SjLj even though
+  // it surely cannot longjmp, in order to maintain the unwind relationship from
+  // all existing catchpads (and calls within them) to catch.dispatch.longjmp.
   //
   // In Wasm EH + Wasm SjLj, we
   // 1. Make all catchswitch and cleanuppad that unwind to caller unwind to
@@ -663,6 +663,8 @@
   //
   // The comment block in findWasmUnwindDestinations() in
   // SelectionDAGBuilder.cpp is addressing a similar problem.
+  if (CalleeName == "__cxa_end_catch")
+    return WebAssembly::WasmEnableSjLj;
   if (CalleeName == "__cxa_begin_catch" ||
       CalleeName == "__cxa_allocate_exception" || CalleeName == "__cxa_throw" ||
       CalleeName == "__clang_call_terminate")


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