[llvm] 468c440 - Revert "[WebAssembly] Rethrow longjmp in EH handling if EmSjLj is enabled"

[Heejin Ahn via llvm-commits]

Author: Heejin Ahn
Date: 2021-09-14T12:59:42-07:00
New Revision: 468c4409f61455a168f9d8c187c75435487adf8c

URL: https://github.com/llvm/llvm-project/commit/468c4409f61455a168f9d8c187c75435487adf8c
DIFF: https://github.com/llvm/llvm-project/commit/468c4409f61455a168f9d8c187c75435487adf8c.diff

LOG: Revert "[WebAssembly] Rethrow longjmp in EH handling if EmSjLj is enabled"

This reverts commit b7b4ebbcfa463a7fae61dca7cec30c5b747bdec8.

Reason: This breaks several code-size tests in Emscripten test suite
because this exports `emscripten_longjmp` for programs that didn't do it
before.

Added: 
    

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

Removed: 
    llvm/test/CodeGen/WebAssembly/lower-em-ehsjlj-sjlj-not-used.ll


################################################################################
diff  --git a/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
index aaeedc2024b4..c67ac527fa15 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
@@ -959,18 +959,6 @@ bool WebAssemblyLowerEmscriptenEHSjLj::runOnModule(Module &M) {
     }
   }
 
-  // Above, we registered emscripten_longjmp function only when it SjLj is
-  // actually used. But there is a case we need emscripten_longjmp when we
-  // rethrow longjmps after checking for an Emscripten exception. Refer to
-  // runEHOnFunction for details.
-  if (EnableEmEH && EnableEmSjLj && !EmLongjmpF) {
-    // Register emscripten_longjmp function
-    FunctionType *FTy = FunctionType::get(
-        IRB.getVoidTy(), {getAddrIntType(&M), IRB.getInt32Ty()}, false);
-    EmLongjmpF = getEmscriptenFunction(FTy, "emscripten_longjmp", &M);
-    EmLongjmpF->addFnAttr(Attribute::NoReturn);
-  }
-
   // Exception handling transformation
   if (EnableEmEH) {
     for (Function &F : M) {
@@ -1048,11 +1036,6 @@ bool WebAssemblyLowerEmscriptenEHSjLj::runEHOnFunction(Function &F) {
       // value is 0 when nothing happened, 1 when an exception is thrown, and
       // other values when longjmp is thrown.
       //
-      // Note that we do this whenever -enable-emscripten-sjlj is on, regardless
-      // of whether there is actual usage of setjmp/longjmp within the module.
-      // Because we use wasm-ld to link files, what we see here is not the whole
-      // program, and there can be a longjmp call in another file.
-      //
       // if (%__THREW__.val == 0 || %__THREW__.val == 1)
       //   goto %tail
       // else
@@ -1064,7 +1047,8 @@ bool WebAssemblyLowerEmscriptenEHSjLj::runEHOnFunction(Function &F) {
       //
       // tail: ;; Nothing happened or an exception is thrown
       //   ... Continue exception handling ...
-      if (EnableEmSjLj && !SetjmpUsers.count(&F) && canLongjmp(Callee)) {
+      if (DoSjLj && EnableEmSjLj && !SetjmpUsers.count(&F) &&
+          canLongjmp(Callee)) {
         // Create longjmp.rethrow BB once and share it within the function
         if (!RethrowLongjmpBB) {
           RethrowLongjmpBB = BasicBlock::Create(C, "rethrow.longjmp", &F);

diff  --git a/llvm/test/CodeGen/WebAssembly/lower-em-ehsjlj-sjlj-not-used.ll b/llvm/test/CodeGen/WebAssembly/lower-em-ehsjlj-sjlj-not-used.ll
deleted file mode 100644
index 4d82d04652da..000000000000
--- a/llvm/test/CodeGen/WebAssembly/lower-em-ehsjlj-sjlj-not-used.ll
+++ /dev/null
@@ -1,59 +0,0 @@
-; RUN: opt < %s -wasm-lower-em-ehsjlj -enable-emscripten-cxx-exceptions -enable-emscripten-sjlj -S | FileCheck %s
-; RUN: llc < %s -enable-emscripten-cxx-exceptions -enable-emscripten-sjlj -verify-machineinstrs
-
-target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
-target triple = "wasm32-unknown-unknown"
-
-; The same test with the same function in lower-em-ehsjlj.ll, both the
-; Emscripten EH and Emscripten SjLj are enabled in the same way, and this
-; function only does exception handling. The 
diff erence is that this module does
-; not contain any calls to setjmp or longjmp.
-;
-; But we still have to check if the thrown value is longjmp and and if so
-; rethrow it by calling @emscripten_longjmp, because we link object files using
-; wasm-ld, so the module we see in LowerEmscriptenEHSjLj pass is not the whole
-; program and there can be a longjmp call within another file.
-define void @rethrow_longjmp() personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
-; CHECK-LABEL: @rethrow_longjmp
-entry:
-  invoke void @foo()
-          to label %try.cont unwind label %lpad
-; CHECK:    entry:
-; CHECK:      %cmp.eq.one = icmp eq i32 %__THREW__.val, 1
-; CHECK-NEXT: %cmp.eq.zero = icmp eq i32 %__THREW__.val, 0
-; CHECK-NEXT: %or = or i1 %cmp.eq.zero, %cmp.eq.one
-; CHECK-NEXT: br i1 %or, label %tail, label %rethrow.longjmp
-
-; CHECK: try.cont:
-; CHECK-NEXT:  %phi = phi i32 [ undef, %tail ], [ undef, %lpad ]
-; CHECK-NEXT:  ret void
-
-; CHECK:    rethrow.longjmp:
-; CHECK-NEXT: %threw.phi = phi i32 [ %__THREW__.val, %entry ]
-; CHECK-NEXT: %__threwValue.val = load i32, i32* @__threwValue, align 4
-; CHECK-NEXT: call void @emscripten_longjmp(i32 %threw.phi, i32 %__threwValue.val
-; CHECK-NEXT: unreachable
-
-; CHECK:    tail:
-; CHECK-NEXT: %cmp = icmp eq i32 %__THREW__.val, 1
-; CHECK-NEXT: br i1 %cmp, label %lpad, label %try.cont
-
-lpad:                                             ; preds = %entry
-  %0 = landingpad { i8*, i32 }
-          catch i8* null
-  %1 = extractvalue { i8*, i32 } %0, 0
-  %2 = extractvalue { i8*, i32 } %0, 1
-  %3 = call i8* @__cxa_begin_catch(i8* %1) #5
-  call void @__cxa_end_catch()
-  br label %try.cont
-
-try.cont:                                         ; preds = %lpad, %entry
- %phi = phi i32 [ undef, %entry ], [ undef, %lpad ]
-  ret void
-}
-
-declare void @foo()
-declare i32 @__gxx_personality_v0(...)
-declare i8* @__cxa_begin_catch(i8*)
-declare void @__cxa_end_catch()
-declare void @__cxa_throw(i8*, i8*, i8*)