Add basic exception handling support (#2282)

This adds basic support for exception handling instructions, according
to the spec:
https://github.com/WebAssembly/exception-handling/blob/master/proposals/Exceptions.md

This PR includes support for:
- Binary reading/writing
- Wast reading/writing
- Stack IR
- Validation
- binaryen.js + C API
- Few IR routines: branch-utils, type-updating, etc
- Few passes: just enough to make `wasm-opt -O` pass
- Tests

This PR does not include support for many optimization passes, fuzzer,
or interpreter. They will be follow-up PRs.

Try-catch construct is modeled in Binaryen IR in a similar manner to
that of if-else: each of try body and catch body will contain a block,
which can be omitted if there is only a single instruction. This block
will not be emitted in wast or binary, as in if-else. As in if-else,
`class Try` contains two expressions each for try body and catch body,
and `catch` is not modeled as an instruction. `exnref` value pushed by
`catch` is get by `pop` instruction.

`br_on_exn` is special: it returns different types of values when taken
and not taken. We make `exnref`, the type `br_on_exn` pushes if not
taken, as `br_on_exn`'s type.

1 files changed, 31 insertions, 0 deletions

diff --git a/src/binaryen-c.h b/src/binaryen-c.h
index dc5d50fef..37e8c3204 100644
--- a/src/binaryen-c.h
+++ b/src/binaryen-c.h
@@ -127,6 +127,10 @@ BinaryenExpressionId BinaryenMemoryInitId(void);
 BinaryenExpressionId BinaryenDataDropId(void);
 BinaryenExpressionId BinaryenMemoryCopyId(void);
 BinaryenExpressionId BinaryenMemoryFillId(void);
+BinaryenExpressionId BinaryenTryId(void);
+BinaryenExpressionId BinaryenThrowId(void);
+BinaryenExpressionId BinaryenRethrowId(void);
+BinaryenExpressionId BinaryenBrOnExnId(void);
 BinaryenExpressionId BinaryenPushId(void);
 BinaryenExpressionId BinaryenPopId(void);
 
@@ -701,6 +705,19 @@ BinaryenExpressionRef BinaryenMemoryFill(BinaryenModuleRef module,
                                          BinaryenExpressionRef dest,
                                          BinaryenExpressionRef value,
                                          BinaryenExpressionRef size);
+BinaryenExpressionRef BinaryenTry(BinaryenModuleRef module,
+                                  BinaryenExpressionRef body,
+                                  BinaryenExpressionRef catchBody);
+BinaryenExpressionRef BinaryenThrow(BinaryenModuleRef module,
+                                    const char* event,
+                                    BinaryenExpressionRef* operands,
+                                    BinaryenIndex numOperands);
+BinaryenExpressionRef BinaryenRethrow(BinaryenModuleRef module,
+                                      BinaryenExpressionRef exnref);
+BinaryenExpressionRef BinaryenBrOnExn(BinaryenModuleRef module,
+                                      const char* name,
+                                      const char* eventName,
+                                      BinaryenExpressionRef exnref);
 BinaryenExpressionRef BinaryenPush(BinaryenModuleRef module,
                                    BinaryenExpressionRef value);
 BinaryenExpressionRef BinaryenPop(BinaryenModuleRef module, BinaryenType type);
@@ -855,6 +872,20 @@ BinaryenExpressionRef BinaryenMemoryFillGetDest(BinaryenExpressionRef expr);
 BinaryenExpressionRef BinaryenMemoryFillGetValue(BinaryenExpressionRef expr);
 BinaryenExpressionRef BinaryenMemoryFillGetSize(BinaryenExpressionRef expr);
 
+BinaryenExpressionRef BinaryenTryGetBody(BinaryenExpressionRef expr);
+BinaryenExpressionRef BinaryenTryGetCatchBody(BinaryenExpressionRef expr);
+
+const char* BinaryenThrowGetEvent(BinaryenExpressionRef expr);
+BinaryenExpressionRef BinaryenThrowGetOperand(BinaryenExpressionRef expr,
+                                              BinaryenIndex index);
+BinaryenIndex BinaryenThrowGetNumOperands(BinaryenExpressionRef expr);
+
+BinaryenExpressionRef BinaryenRethrowGetExnref(BinaryenExpressionRef expr);
+
+const char* BinaryenBrOnExnGetEvent(BinaryenExpressionRef expr);
+const char* BinaryenBrOnExnGetName(BinaryenExpressionRef expr);
+BinaryenExpressionRef BinaryenBrOnExnGetExnref(BinaryenExpressionRef expr);
+
 BinaryenExpressionRef BinaryenPushGetValue(BinaryenExpressionRef expr);
 
 // Functions