[WebAssembly] Support instruction selection for catching exceptions

Summary:
This lowers exception catching-related instructions:
1. Lowers `wasm.catch` intrinsic to `catch` instruction
2. Removes `catchpad` and `cleanuppad` instructions; they are not
necessary after isel phase. (`MachineBasicBlock::isEHFuncletEntry()` or
`MachineBasicBlock::isEHPad()` can be used instead.)
3. Lowers `catchret` and `cleanupret` instructions to pseudo `catchret`
and `cleanupret` instructions in isel, which will be replaced with other
instructions in `WebAssemblyExceptionPrepare` pass.
4. Adds 'WebAssemblyExceptionPrepare` pass, which is for running various
transformation for EH. Currently this pass only replaces `catchret` and
`cleanupret` instructions into appropriate wasm instructions to make
this patch successfully run until the end.

Currently this does not handle lowering of intrinsics related to LSDA
info generation (`wasm.landingpad.index` and `wasm.lsda`), because they
cannot be tested without implementing `EHStreamer`'s wasm-specific
handlers. They are marked as TODO, which is needed to make isel pass.
Also this does not generate `try` and `end_try` markers yet, which will
be handled in later patches.

This patch is based on the first wasm EH proposal.
(https://github.com/WebAssembly/exception-handling/blob/master/proposals/Exceptions.md)

Reviewers: dschuff, majnemer

Subscribers: jfb, sbc100, jgravelle-google, sunfish, llvm-commits

Differential Revision: https://reviews.llvm.org/D44090

llvm-svn: 333705

1 files changed, 75 insertions, 8 deletions

diff --git a/llvm/test/CodeGen/WebAssembly/exception.ll b/llvm/test/CodeGen/WebAssembly/exception.ll
index 014b52027cc..c4d4a6a1d89 100644
--- a/llvm/test/CodeGen/WebAssembly/exception.ll
+++ b/llvm/test/CodeGen/WebAssembly/exception.ll
@@ -1,22 +1,89 @@
-; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -disable-wasm-explicit-locals | FileCheck %s
+; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -exception-model=wasm | FileCheck %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*
+
 declare void @llvm.wasm.throw(i32, i8*)
-declare void @llvm.wasm.rethrow()
 
-; CHECK-LABEL: throw:
+; CHECK-LABEL: test_throw:
 ; CHECK-NEXT: i32.const $push0=, 0
 ; CHECK-NEXT: throw 0, $pop0
-define void @throw() {
+define void @test_throw() {
   call void @llvm.wasm.throw(i32 0, i8* null)
   ret void
 }
 
-; CHECK-LABEL: rethrow:
-; CHECK-NEXT: rethrow 0
-define void @rethrow() {
-  call void @llvm.wasm.rethrow()
+; CHECK-LABEL: test_catch:
+; CHECK:   call      foo@FUNCTION
+; CHECK:   i32.catch     $push{{.+}}=, 0
+; CHECK-DAG:   i32.store  __wasm_lpad_context
+; CHECK-DAG:   i32.store  __wasm_lpad_context+4
+; CHECK:   i32.call  $push{{.+}}=, _Unwind_CallPersonality@FUNCTION
+; CHECK:   i32.call  $push{{.+}}=, __cxa_begin_catch@FUNCTION
+; CHECK:   call      __cxa_end_catch@FUNCTION
+; CHECK:   call      __cxa_rethrow@FUNCTION
+define void @test_catch() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
+entry:
+  invoke void @foo()
+          to label %try.cont unwind label %catch.dispatch
+
+catch.dispatch:                                   ; preds = %entry
+  %0 = catchswitch within none [label %catch.start] unwind to caller
+
+catch.start:                                      ; preds = %catch.dispatch
+  %1 = catchpad within %0 [i8* bitcast (i8** @_ZTIi to i8*)]
+  %2 = call i8* @llvm.wasm.get.exception(token %1)
+  %3 = call i32 @llvm.wasm.get.ehselector(token %1)
+  %4 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIi to i8*))
+  %matches = icmp eq i32 %3, %4
+  br i1 %matches, label %catch, label %rethrow
+
+catch:                                            ; preds = %catch.start
+  %5 = call i8* @__cxa_begin_catch(i8* %2) [ "funclet"(token %1) ]
+  call void @__cxa_end_catch() [ "funclet"(token %1) ]
+  catchret from %1 to label %try.cont
+
+rethrow:                                          ; preds = %catch.start
+  call void @__cxa_rethrow() [ "funclet"(token %1) ]
+  unreachable
+
+try.cont:                                         ; preds = %entry, %catch
   ret void
 }
+
+; CHECK-LABEL: test_cleanup:
+; CHECK:   call      foo@FUNCTION
+; CHECK:   return
+; CHECK:   i32.call  $push20=, _ZN7CleanupD1Ev@FUNCTION
+; CHECK:   rethrow   0
+define void @test_cleanup() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
+entry:
+  %c = alloca %struct.Cleanup, align 1
+  invoke void @foo()
+          to label %invoke.cont unwind label %ehcleanup
+
+invoke.cont:                                      ; preds = %entry
+  %call = call %struct.Cleanup* @_ZN7CleanupD1Ev(%struct.Cleanup* %c)
+  ret void
+
+ehcleanup:                                        ; preds = %entry
+  %0 = cleanuppad within none []
+  %call1 = call %struct.Cleanup* @_ZN7CleanupD1Ev(%struct.Cleanup* %c) [ "funclet"(token %0) ]
+  cleanupret from %0 unwind to caller
+}
+
+declare void @foo()
+declare void @func(i32)
+declare i32 @__gxx_wasm_personality_v0(...)
+declare i8* @llvm.wasm.get.exception(token)
+declare i32 @llvm.wasm.get.ehselector(token)
+declare i32 @llvm.eh.typeid.for(i8*)
+declare i8* @__cxa_begin_catch(i8*)
+declare void @__cxa_end_catch()
+declare void @__cxa_rethrow()
+declare void @__clang_call_terminate(i8*)
+declare %struct.Cleanup* @_ZN7CleanupD1Ev(%struct.Cleanup* returned)