[WebAssembly] Exception handling: Switch to the new proposal

Summary:
This switches the EH implementation to the new proposal:
https://github.com/WebAssembly/exception-handling/blob/master/proposals/Exceptions.md
(The previous proposal was
 https://github.com/WebAssembly/exception-handling/blob/master/proposals/old/Exceptions.md)

- Instruction changes
  - Now we have one single `catch` instruction that returns a except_ref
    value
  - `throw` now can take variable number of operations
  - `rethrow` does not have 'depth' argument anymore
  - `br_on_exn` queries an except_ref to see if it matches the tag and
    branches to the given label if true.
  - `extract_exception` is a pseudo instruction that simulates popping
    values from wasm stack. This is to make `br_on_exn`, a very special
    instruction, work: `br_on_exn` puts values onto the stack only if it
    is taken, and the # of values can vay depending on the tag.

- Now there's only one `catch` per `try`, this patch removes all special
  handling for terminate pad with a call to `__clang_call_terminate`.
  Before it was the only case there are two catch clauses (a normal
  `catch` and `catch_all` per `try`).

- Make `rethrow` act as a terminator like `throw`. This splits BB after
  `rethrow` in WasmEHPrepare, and deletes an unnecessary `unreachable`
  after `rethrow` in LateEHPrepare.

- Now we stop at all catchpads (because we add wasm `catch` instruction
  that catches all exceptions), this creates new
  `findWasmUnwindDestinations` function in SelectionDAGBuilder.

- Now we use `br_on_exn` instrution to figure out if an except_ref
  matches the current tag or not, LateEHPrepare generates this sequence
  for catch pads:
```
  catch
  block i32
  br_on_exn $__cpp_exception
  end_block
  extract_exception
```

- Branch analysis for `br_on_exn` in WebAssemblyInstrInfo

- Other various misc. changes to switch to the new proposal.

Reviewers: dschuff

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

Differential Revision: https://reviews.llvm.org/D57134

llvm-svn: 352598

1 files changed, 10 insertions, 142 deletions

diff --git a/llvm/unittests/Target/WebAssembly/WebAssemblyExceptionInfoTest.cpp b/llvm/unittests/Target/WebAssembly/WebAssemblyExceptionInfoTest.cpp
index 0ecfdad462a..ec946379b1e 100644
--- a/llvm/unittests/Target/WebAssembly/WebAssemblyExceptionInfoTest.cpp
+++ b/llvm/unittests/Target/WebAssembly/WebAssemblyExceptionInfoTest.cpp
@@ -74,7 +74,7 @@ TEST(WebAssemblyExceptionInfoTest, TEST0) {
 
   declare i32 @__gxx_wasm_personality_v0(...)
 
-  define hidden void @test0() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
+  define void @test0() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
     unreachable
   }
 
@@ -100,14 +100,14 @@ body: |
   ; predecessors: %bb.0
     successors: %bb.3, %bb.9
     liveins: $value_stack
-    CATCH_ALL implicit-def $arguments
+    %0:except_ref = CATCH implicit-def $arguments
     CLEANUPRET implicit-def dead $arguments
 
   bb.3 (landing-pad):
   ; predecessors: %bb.2
     successors: %bb.4, %bb.6
     liveins: $value_stack
-    CATCH_ALL implicit-def $arguments
+    %1:except_ref = CATCH implicit-def $arguments
     BR_IF %bb.4, %58:i32, implicit-def $arguments, implicit-def $value_stack, implicit $value_stack
     BR %bb.6, implicit-def $arguments
 
@@ -138,13 +138,13 @@ body: |
   ; predecessors: %bb.4
     successors: %bb.9
     liveins: $value_stack
-    CATCH_ALL implicit-def $arguments
+    %2:except_ref = CATCH implicit-def $arguments
     CLEANUPRET implicit-def dead $arguments
 
   bb.9 (landing-pad):
   ; predecessors: %bb.2, %bb.6, %bb.8
     liveins: $value_stack
-    CATCH_ALL implicit-def $arguments
+    %3:except_ref = CATCH implicit-def $arguments
     CLEANUPRET implicit-def dead $arguments
 
   bb.10:
@@ -237,7 +237,7 @@ TEST(WebAssemblyExceptionInfoTest, TEST1) {
 
   declare i32 @__gxx_wasm_personality_v0(...)
 
-  define hidden void @test1() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
+  define void @test1() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
     unreachable
   }
 
@@ -257,7 +257,7 @@ body: |
   ; predecessors: %bb.0
     successors: %bb.2, %bb.8
     liveins: $value_stack
-    %52:i32 = CATCH_I32 0, implicit-def dead $arguments
+    %0:except_ref = CATCH implicit-def $arguments
     BR_IF %bb.2, %32:i32, implicit-def $arguments, implicit-def $value_stack, implicit $value_stack
     BR %bb.8, implicit-def $arguments
 
@@ -271,7 +271,7 @@ body: |
   ; predecessors: %bb.2
     successors: %bb.4, %bb.6
     liveins: $value_stack
-    CATCH_ALL implicit-def $arguments
+    %1:except_ref = CATCH implicit-def $arguments
     BR_IF %bb.4, %43:i32, implicit-def $arguments, implicit-def $value_stack, implicit $value_stack
     BR %bb.6, implicit-def $arguments
 
@@ -313,13 +313,13 @@ body: |
   ; predecessors: %bb.4
     successors: %bb.11
     liveins: $value_stack
-    CATCH_ALL implicit-def $arguments
+    %2:except_ref = CATCH implicit-def $arguments
     CLEANUPRET implicit-def dead $arguments
 
   bb.11 (landing-pad):
   ; predecessors: %bb.2, %bb.6, %bb.10
     liveins: $value_stack
-    CATCH_ALL implicit-def $arguments
+    %3:except_ref = CATCH implicit-def $arguments
     CLEANUPRET implicit-def dead $arguments
 
   bb.12:
@@ -415,135 +415,3 @@ body: |
   EXPECT_EQ(WE0_1->getParentException(), WE0);
   EXPECT_EQ(WE0_1->getExceptionDepth(), (unsigned)2);
 }
-
-// Terminate pad test
-TEST(WebAssemblyExceptionInfoTest, TEST2) {
-  std::unique_ptr<LLVMTargetMachine> TM = createTargetMachine();
-  ASSERT_TRUE(TM);
-
-  StringRef MIRString = R"MIR(
---- |
-  target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
-  target triple = "wasm32-unknown-unknown"
-
-  declare i32 @__gxx_wasm_personality_v0(...)
-  declare void @_ZSt9terminatev()
-  declare void @__clang_call_terminate(i8*)
-
-  define hidden void @test2() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
-    unreachable
-  }
-
-...
----
-name: test2
-liveins:
-  - { reg: '$arguments' }
-  - { reg: '$value_stack' }
-body: |
-  bb.0:
-    successors: %bb.3, %bb.1
-    BR %bb.3, implicit-def dead $arguments
-
-  bb.1 (landing-pad):
-  ; predecessors: %bb.0
-    successors: %bb.2, %bb.4
-    %3:i32 = CATCH_I32 0, implicit-def dead $arguments
-    BR %bb.2, implicit-def dead $arguments
-
-  bb.2:
-  ; predecessors: %bb.1
-    successors: %bb.3(0x80000000); %bb.3(200.00%)
-    CATCHRET %bb.3, %bb.0, implicit-def dead $arguments
-
-  bb.3:
-  ; predecessors: %bb.0, %bb.2
-    RETURN_VOID implicit-def $arguments
-
-  bb.4 (landing-pad):
-  ; predecessors: %bb.1
-    successors: %bb.5, %bb.6
-    CATCH_ALL implicit-def $arguments
-    BR %bb.5, implicit-def dead $arguments
-
-  bb.5:
-  ; predecessors: %bb.4
-    CLEANUPRET implicit-def dead $arguments
-
-  bb.6 (landing-pad):
-  ; predecessors: %bb.4
-    successors: %bb.7(0x80000000); %bb.7(200.00%)
-    %6:i32 = CATCH_I32 0, implicit-def dead $arguments
-    CALL_VOID @__clang_call_terminate, %7:i32, implicit-def $arguments
-    UNREACHABLE implicit-def $arguments
-
-  bb.7 (landing-pad):
-  ; predecessors: %bb.6
-    CATCH_ALL implicit-def $arguments
-    CALL_VOID @_ZSt9terminatev, implicit-def $arguments
-    UNREACHABLE implicit-def $arguments
-)MIR";
-
-  LLVMContext Context;
-  std::unique_ptr<MIRParser> MIR;
-  MachineModuleInfo MMI(TM.get());
-  std::unique_ptr<Module> M =
-      parseMIR(Context, MIR, *TM, MIRString, "test2", MMI);
-  ASSERT_TRUE(M);
-
-  Function *F = M->getFunction("test2");
-  auto *MF = MMI.getMachineFunction(*F);
-  ASSERT_TRUE(MF);
-
-  WebAssemblyExceptionInfo WEI;
-  MachineDominatorTree MDT;
-  MachineDominanceFrontier MDF;
-  MDT.runOnMachineFunction(*MF);
-  MDF.getBase().analyze(MDT.getBase());
-  WEI.recalculate(MDT, MDF);
-
-  // Exception info structure:
-  // |- bb1 (ehpad), bb2, bb4, bb5, bb6, bb7
-  //   |- bb4 (ehpad), bb5, bb6, bb7
-  //     |- bb6 (ehpad), bb7
-  //
-  // Here, bb6 is a terminate pad with a 'catch' instruction, and bb7 is a
-  // terminate pad with a 'catch_all' instruction, In this case we put bb6 and
-  // bb7 into one exception.
-
-  auto *MBB1 = MF->getBlockNumbered(1);
-  auto *WE0 = WEI.getExceptionFor(MBB1);
-  ASSERT_TRUE(WE0);
-  EXPECT_EQ(WE0->getEHPad(), MBB1);
-  EXPECT_EQ(WE0->getParentException(), nullptr);
-  EXPECT_EQ(WE0->getExceptionDepth(), (unsigned)1);
-
-  auto *MBB2 = MF->getBlockNumbered(2);
-  WE0 = WEI.getExceptionFor(MBB2);
-  ASSERT_TRUE(WE0);
-  EXPECT_EQ(WE0->getEHPad(), MBB1);
-
-  auto *MBB4 = MF->getBlockNumbered(4);
-  auto *WE0_0 = WEI.getExceptionFor(MBB4);
-  ASSERT_TRUE(WE0_0);
-  EXPECT_EQ(WE0_0->getEHPad(), MBB4);
-  EXPECT_EQ(WE0_0->getParentException(), WE0);
-  EXPECT_EQ(WE0_0->getExceptionDepth(), (unsigned)2);
-
-  auto *MBB5 = MF->getBlockNumbered(5);
-  WE0_0 = WEI.getExceptionFor(MBB5);
-  ASSERT_TRUE(WE0_0);
-  EXPECT_EQ(WE0_0->getEHPad(), MBB4);
-
-  auto *MBB6 = MF->getBlockNumbered(6);
-  auto *WE0_0_0 = WEI.getExceptionFor(MBB6);
-  ASSERT_TRUE(WE0_0_0);
-  EXPECT_EQ(WE0_0_0->getEHPad(), MBB6);
-  EXPECT_EQ(WE0_0_0->getParentException(), WE0_0);
-  EXPECT_EQ(WE0_0_0->getExceptionDepth(), (unsigned)3);
-
-  auto *MBB7 = MF->getBlockNumbered(7);
-  WE0_0_0 = WEI.getExceptionFor(MBB7);
-  ASSERT_TRUE(WE0_0_0);
-  EXPECT_EQ(WE0_0_0->getEHPad(), MBB6);
-}