[WebAssembly] Split BBs after throw instructions

Summary:
`throw` instruction is a terminator in wasm, but BBs were not splitted
after `throw` instructions, causing machine instruction verifier to
fail.

This patch
- Splits BBs after `throw` instructions in WasmEHPrepare and adding an
  unreachable instruction after `throw`, which will be deleted in
  LateEHPrepare pass
- Refactors WasmEHPrepare into two member functions
- Changes the semantics of `eraseBBsAndChildren` in LateEHPrepare pass
  to match that of WasmEHPrepare pass, which is newly added. Now
  `eraseBBsAndChildren` does not delete BBs with remaining predecessors.
- Fixes style nits, making static function names conform to clang-tidy
- Re-enables the test temporarily disabled by rL346840 && rL346845

Reviewers: dschuff

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

Differential Revision: https://reviews.llvm.org/D54571

llvm-svn: 347003

2 files changed, 34 insertions, 5 deletions

diff --git a/llvm/test/CodeGen/WebAssembly/exception.ll b/llvm/test/CodeGen/WebAssembly/exception.ll
index 0577cd43b97..b53cd0cb544 100644
--- a/llvm/test/CodeGen/WebAssembly/exception.ll
+++ b/llvm/test/CodeGen/WebAssembly/exception.ll
@@ -1,5 +1,5 @@
 ; RUN: not llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-keep-registers -exception-model=wasm
-; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-keep-registers -exception-model=wasm -mattr=+exception-handling | FileCheck -allow-deprecated-dag-overlap %s
+; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-keep-registers -exception-model=wasm -mattr=+exception-handling -verify-machineinstrs | FileCheck -allow-deprecated-dag-overlap %s
 ; RUN: llc < %s -disable-wasm-fallthrough-return-opt -wasm-keep-registers -exception-model=wasm -mattr=+exception-handling
 
 target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
@@ -12,10 +12,11 @@ target triple = "wasm32-unknown-unknown"
 declare void @llvm.wasm.throw(i32, i8*)
 
 ; CHECK-LABEL: test_throw:
-; CHECK-NEXT: i32.const $push0=, 0
+; CHECK:      get_local $push0=, 0
 ; CHECK-NEXT: throw __cpp_exception@EVENT, $pop0
-define void @test_throw() {
-  call void @llvm.wasm.throw(i32 0, i8* null)
+; CHECK-NOT:  unreachable
+define void @test_throw(i8* %p) {
+  call void @llvm.wasm.throw(i32 0, i8* %p)
   ret void
 }
 
diff --git a/llvm/test/CodeGen/WebAssembly/wasmehprepare.ll b/llvm/test/CodeGen/WebAssembly/wasmehprepare.ll
index 67e198eb058..6df7175b1ca 100644
--- a/llvm/test/CodeGen/WebAssembly/wasmehprepare.ll
+++ b/llvm/test/CodeGen/WebAssembly/wasmehprepare.ll
@@ -298,6 +298,34 @@ try.cont10:                                       ; preds = %invoke.cont3, %catc
   ret void
 }
 
+; Tests if instructions after a call to @llvm.wasm.throw are deleted and the
+; BB's dead children are deleted.
+
+; CHECK-LABEL: @test6
+define i32 @test6(i1 %b, i8* %p) {
+entry:
+  br i1 %b, label %bb.true, label %bb.false
+
+; CHECK:      bb.true:
+; CHECK-NEXT:   call void @llvm.wasm.throw(i32 0, i8* %p)
+; CHECK-NEXT:   unreachable
+bb.true:                                          ; preds = %entry
+  call void @llvm.wasm.throw(i32 0, i8* %p)
+  br label %bb.true.0
+
+; CHECK-NOT:  bb.true.0
+bb.true.0:                                        ; preds = %bb.true
+  br label %merge
+
+; CHECK:      bb.false
+bb.false:                                         ; preds = %entry
+  br label %merge
+
+; CHECK:      merge
+merge:                                            ; preds = %bb.true.0, %bb.false
+  ret i32 0
+}
+
 declare void @foo()
 declare void @func(i32)
 declare %struct.Cleanup* @_ZN7CleanupD1Ev(%struct.Cleanup* returned)
@@ -305,6 +333,7 @@ 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 void @llvm.wasm.throw(i32, i8*)
 declare i8* @__cxa_begin_catch(i8*)
 declare void @__cxa_end_catch()
 declare void @__cxa_rethrow()
@@ -314,4 +343,3 @@ declare void @__clang_call_terminate(i8*)
 ; CHECK-DAG: declare void @llvm.wasm.landingpad.index(token, i32)
 ; CHECK-DAG: declare i8* @llvm.wasm.lsda()
 ; CHECK-DAG: declare i32 @_Unwind_CallPersonality(i8*)
-