[WebAssembly] Add missing -mattr=+exception-handling guards

[aheejin]

Summary

The use of exception handling instructions should only be enabled with
-mattr=+exception-handling option.

[aheejin]

Ping

[aheejin]

This comment was removed by aheejin.

[aheejin]

@jgravelle-google ping

lib/Target/WebAssembly/WebAssemblyInstrControl.td

 
 defm UNREACHABLE : NRI<(outs), (ins), [(trap)], "unreachable", 0x00>;
 } // isTerminator = 1, hasCtrlDep = 1, isBarrier = 1
 
 //===----------------------------------------------------------------------===//
 // Exception handling instructions
 //===----------------------------------------------------------------------===//
 
+let Predicates = [HasExceptionHandling] in {
+
 // Throwing an exception: throw / rethrow
 let isTerminator = 1, hasCtrlDep = 1, isBarrier = 1 in {
 defm THROW_I32 : I<(outs), (ins i32imm:$tag, I32:$val),
                    (outs), (ins i32imm:$tag),
                    [(int_wasm_throw imm:$tag, I32:$val)],
                    "throw   \t$tag, $val", "throw   \t$tag",
                    0x08>;
 defm THROW_I64 : I<(outs), (ins i32imm:$tag, I64:$val),

 // They are not return instructions in wasm, but setting 'isReturn' to true as
 // in X86 is necessary for computing EH scope membership.
 let isTerminator = 1, hasSideEffects = 1, isBarrier = 1, hasCtrlDep = 1,
     isCodeGenOnly = 1, isReturn = 1 in {
   defm CLEANUPRET : NRI<(outs), (ins), [(cleanupret)], "", 0>;
   defm CATCHRET : NRI<(outs), (ins bb_op:$dst, bb_op:$from),
                    [(catchret bb:$dst, bb:$from)], "", 0>;
 }
+}
 
 } // Defs = [ARGUMENTS]

test/CodeGen/WebAssembly/exception.ll

-; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -exception-model=wasm | FileCheck -allow-deprecated-dag-overlap %s
+; RUN: not llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -exception-model=wasm
+; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -exception-model=wasm -mattr=+exception-handling | FileCheck -allow-deprecated-dag-overlap %s
 
 target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
 target triple = "wasm32-unknown-unknown"
 
 %struct.Cleanup = type { i8 }
 
 @_ZTIi = external constant i8*