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[WebAssembly] Fix JS code mentions in LowerEmscriptenEHSjLj

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- Removes the mention of fastcomp, which is deprecated.
- Some functions in Emscripten have moved from JS glue code to
  compiler-rt/emscripten_setjmp.c and
  compiler-rt/emscripten_exception_builtins.c. This fixes comments about
  that.

Reviewed By: sbc100

Differential Revision: https://reviews.llvm.org/D101812
This commit is contained in:
Heejin Ahn 2021-05-03 21:48:38 -07:00
parent 535cbe02a4
commit 7f06cae1c1
1 changed files with 14 additions and 28 deletions
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42
llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
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@ -13,14 +13,7 @@
///
/// To handle exceptions and setjmp/longjmps, this scheme relies on JavaScript's
/// try and catch syntax and relevant exception-related libraries implemented
/// in JavaScript glue code that will be produced by Emscripten. This is similar
/// to the current Emscripten asm.js exception handling in fastcomp. For
/// fastcomp's EH / SjLj scheme, see these files in fastcomp LLVM branch:
/// (Location: https://github.com/kripken/emscripten-fastcomp)
/// lib/Target/JSBackend/NaCl/LowerEmExceptionsPass.cpp
/// lib/Target/JSBackend/NaCl/LowerEmSetjmp.cpp
/// lib/Target/JSBackend/JSBackend.cpp
/// lib/Target/JSBackend/CallHandlers.h
/// in JavaScript glue code that will be produced by Emscripten.
///
/// * Exception handling
/// This pass lowers invokes and landingpads into library functions in JS glue
@ -50,9 +43,8 @@
/// In detail, this pass does following things:
///
/// 1) Assumes the existence of global variables: __THREW__, __threwValue
/// __THREW__ and __threwValue will be set in invoke wrappers
/// in JS glue code. For what invoke wrappers are, refer to 3). These
/// variables are used for both exceptions and setjmp/longjmps.
/// __THREW__ and __threwValue are defined in compiler-rt in Emscripten.
/// These variables are used for both exceptions and setjmp/longjmps.
/// __THREW__ indicates whether an exception or a longjmp occurred or not. 0
/// means nothing occurred, 1 means an exception occurred, and other numbers
/// mean a longjmp occurred. In the case of longjmp, __threwValue variable
@ -61,14 +53,9 @@
/// * Exception handling
///
/// 2) We assume the existence of setThrew and setTempRet0/getTempRet0 functions
/// at link time.
/// The global variables in 1) will exist in wasm address space,
/// but their values should be set in JS code, so these functions
/// as interfaces to JS glue code. These functions are equivalent to the
/// following JS functions, which actually exist in asm.js version of JS
/// library.
/// at link time. setThrew exists in Emscripten's compiler-rt:
///
/// function setThrew(threw, value) {
/// void setThrew(int threw, int value) {
/// if (__THREW__ == 0) {
/// __THREW__ = threw;
/// __threwValue = value;
@ -76,7 +63,6 @@
/// }
//
/// setTempRet0 is called from __cxa_find_matching_catch() in JS glue code.
///
/// In exception handling, getTempRet0 indicates the type of an exception
/// caught, and in setjmp/longjmp, it means the second argument to longjmp
/// function.
@ -105,7 +91,7 @@
/// Module["dynCall_vi"](index,a1); // This calls original callee
/// } catch(e) {
/// if (typeof e !== 'number' && e !== 'longjmp') throw e;
/// asm["setThrew"](1, 0); // setThrew is called here
/// _setThrew(1, 0); // setThrew is called here
/// }
/// }
/// If an exception is thrown, __THREW__ will be set to true in a wrapper,
@ -149,8 +135,8 @@
/// setjmpTableSize = 4;
/// setjmpTable = (int *) malloc(40);
/// setjmpTable[0] = 0;
/// setjmpTable and setjmpTableSize are used in saveSetjmp() function in JS
/// code.
/// setjmpTable and setjmpTableSize are used to call saveSetjmp() function in
/// Emscripten compiler-rt.
///
/// 3) Lower
/// setjmp(buf)
@ -160,11 +146,11 @@
/// For each dynamic setjmp call, setjmpTable stores its ID (a number which
/// is incrementally assigned from 0) and its label (a unique number that
/// represents each callsite of setjmp). When we need more entries in
/// setjmpTable, it is reallocated in saveSetjmp() in JS code and it will
/// return the new table address, and assign the new table size in
/// setTempRet0(). saveSetjmp also stores the setjmp's ID into the buffer
/// buf. A BB with setjmp is split into two after setjmp call in order to
/// make the post-setjmp BB the possible destination of longjmp BB.
/// setjmpTable, it is reallocated in saveSetjmp() in Emscripten's
/// compiler-rt and it will return the new table address, and assign the new
/// table size in setTempRet0(). saveSetjmp also stores the setjmp's ID into
/// the buffer buf. A BB with setjmp is split into two after setjmp call in
/// order to make the post-setjmp BB the possible destination of longjmp BB.
///
///
/// 4) Lower every call that might longjmp into
@ -505,7 +491,7 @@ bool WebAssemblyLowerEmscriptenEHSjLj::canLongjmp(Module &M,
if (CalleeName == "setjmp" || CalleeName == "malloc" || CalleeName == "free")
return false;
// There are functions in JS glue code
// There are functions in Emscripten's JS glue code or compiler-rt
if (CalleeName == "__resumeException" || CalleeName == "llvm_eh_typeid_for" ||
CalleeName == "saveSetjmp" || CalleeName == "testSetjmp" ||
CalleeName == "getTempRet0" || CalleeName == "setTempRet0")