[llvm] d9517ef - [WebAssembly] Treat __cxa_end_catch not longjmpable in Emscripten SjLj

[Heejin Ahn via llvm-commits]

Author: Heejin Ahn
Date: 2022-01-27T21:03:23-08:00
New Revision: d9517efbb3dc24e725b397031b3bffc6c5c1004e

URL: https://github.com/llvm/llvm-project/commit/d9517efbb3dc24e725b397031b3bffc6c5c1004e
DIFF: https://github.com/llvm/llvm-project/commit/d9517efbb3dc24e725b397031b3bffc6c5c1004e.diff

LOG: [WebAssembly] Treat __cxa_end_catch not longjmpable in Emscripten SjLj

In D117610 we treated `__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.

Reviewed By: dschuff

Differential Revision: https://reviews.llvm.org/D117943

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
index fe656753889f..85fe6ea40a66 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
@@ -630,9 +630,9 @@ static bool canLongjmp(const Value *Callee) {
 
   // 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 @@ static bool canLongjmp(const Value *Callee) {
   //
   // 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")

diff  --git a/llvm/test/CodeGen/WebAssembly/lower-em-ehsjlj.ll b/llvm/test/CodeGen/WebAssembly/lower-em-ehsjlj.ll
index 85229ef101f4..9d03ee6d71a7 100644
--- a/llvm/test/CodeGen/WebAssembly/lower-em-ehsjlj.ll
+++ b/llvm/test/CodeGen/WebAssembly/lower-em-ehsjlj.ll
@@ -33,21 +33,23 @@ entry:
 ; 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