[PATCH] D65475: Fix __clang_call_termiante's argument for foreign exceptions

[Heejin Ahn via Phabricator via llvm-commits]

aheejin created this revision.
aheejin added a reviewer: dschuff.
Herald added subscribers: llvm-commits, hiraditya, jgravelle-google, sbc100.
Herald added a project: LLVM.

When exceptions are repeatedly thrown in the middle of handling another
exception, we call `__clang_call_terminate` with the exception pointer
(i32) as an argument. But in case of foreign exceptions, we don't have
the pointer, so we call the function with 0. (This requires
`__clang_call_terminate` can deal with 0 argument, which will be done
later)

But previously the 0 argument was not added as a `i32.const 0` but an
immediate by mistake, causing the `call` instruction to take not an i32
but rather an exnref, because an `exnref` is left on top of the value
stack if `br_on_exn` is not taken.

  block i32
    br_on_exn 0, __cpp_exception
                                 ;; exnref is on top of stack now
    i32.const 0                  ;; This was missing!
    call __clang_call_terminate
    unreachable
  end
  call __clang_call_terminate    ;; This takes i32 extracted by br_on_exn


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D65475

Files:
  llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
  llvm/test/CodeGen/WebAssembly/exception.ll


Index: llvm/test/CodeGen/WebAssembly/exception.ll
===================================================================
--- llvm/test/CodeGen/WebAssembly/exception.ll
+++ llvm/test/CodeGen/WebAssembly/exception.ll
@@ -138,7 +138,8 @@
 ; CHECK:     catch
 ; CHECK:       block     i32
 ; CHECK:         br_on_exn   0, __cpp_exception
-; CHECK:         call      __clang_call_terminate, 0
+; CHECK:         i32.const  ${{.*}}=, 0
+; CHECK:         call      __clang_call_terminate
 ; CHECK:         unreachable
 ; CHECK:       end_block
 ; CHECK:       call      __clang_call_terminate
Index: llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
===================================================================
--- llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
+++ llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
@@ -233,6 +233,7 @@
 // it. The pseudo instruction will be deleted later.
 bool WebAssemblyLateEHPrepare::addExceptionExtraction(MachineFunction &MF) {
   const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
+  MachineRegisterInfo &MRI = MF.getRegInfo();
   auto *EHInfo = MF.getWasmEHFuncInfo();
   SmallVector<MachineInstr *, 16> ExtractInstrs;
   SmallVector<MachineInstr *, 8> ToDelete;
@@ -339,9 +340,11 @@
               WebAssembly::ClangCallTerminateFn);
       assert(ClangCallTerminateFn &&
              "There is no __clang_call_terminate() function");
+      unsigned Reg = MRI.createVirtualRegister(&WebAssembly::I32RegClass);
+      BuildMI(ElseMBB, DL, TII.get(WebAssembly::CONST_I32), Reg).addImm(0);
       BuildMI(ElseMBB, DL, TII.get(WebAssembly::CALL_VOID))
           .addGlobalAddress(ClangCallTerminateFn)
-          .addImm(0);
+          .addReg(Reg);
       BuildMI(ElseMBB, DL, TII.get(WebAssembly::UNREACHABLE));
 
     } else {


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