bjoernager/rust
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wasm exception handling

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This commit is contained in:
Jan-Mirko Otter 2023-05-01 19:24:21 +00:00
parent 35cdb28c84
commit 82730b4521
5 changed files with 117 additions and 14 deletions
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78
compiler/rustc_codegen_llvm/src/intrinsic.rs
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@ -7,7 +7,7 @@ use crate::type_of::LayoutLlvmExt;
use crate::va_arg::emit_va_arg;
use crate::value::Value;
use rustc_codegen_ssa::base::{compare_simd_types, wants_msvc_seh};
use rustc_codegen_ssa::base::{compare_simd_types, wants_msvc_seh, wants_wasm_eh};
use rustc_codegen_ssa::common::{IntPredicate, TypeKind};
use rustc_codegen_ssa::errors::{ExpectedPointerMutability, InvalidMonomorphization};
use rustc_codegen_ssa::mir::operand::OperandRef;
@ -452,6 +452,8 @@ fn try_intrinsic<'ll>(
bx.store(bx.const_i32(0), dest, ret_align);
} else if wants_msvc_seh(bx.sess()) {
codegen_msvc_try(bx, try_func, data, catch_func, dest);
} else if wants_wasm_eh(bx.sess()) {
codegen_wasm_try(bx, try_func, data, catch_func, dest);
} else if bx.sess().target.os == "emscripten" {
codegen_emcc_try(bx, try_func, data, catch_func, dest);
} else {
@ -610,6 +612,80 @@ fn codegen_msvc_try<'ll>(
bx.store(ret, dest, i32_align);
}
// WASM's definition of the `rust_try` function.
fn codegen_wasm_try<'ll>(
bx: &mut Builder<'_, 'll, '_>,
try_func: &'ll Value,
data: &'ll Value,
catch_func: &'ll Value,
dest: &'ll Value,
) {
let (llty, llfn) = get_rust_try_fn(bx, &mut |mut bx| {
bx.set_personality_fn(bx.eh_personality());
let normal = bx.append_sibling_block("normal");
let catchswitch = bx.append_sibling_block("catchswitch");
let catchpad = bx.append_sibling_block("catchpad");
let caught = bx.append_sibling_block("caught");
let try_func = llvm::get_param(bx.llfn(), 0);
let data = llvm::get_param(bx.llfn(), 1);
let catch_func = llvm::get_param(bx.llfn(), 2);
// We're generating an IR snippet that looks like:
//
// declare i32 @rust_try(%try_func, %data, %catch_func) {
// %slot = alloca i8*
// invoke %try_func(%data) to label %normal unwind label %catchswitch
//
// normal:
// ret i32 0
//
// catchswitch:
// %cs = catchswitch within none [%catchpad_rust] unwind to caller
//
// catchpad:
// %tok = catchpad within %cs [null]
// %ptr = call @llvm.wasm.get.exception(token %tok)
// %sel = call @llvm.wasm.get.ehselector(token %tok)
// call %catch_func(%data, %ptr)
// catchret from %tok to label %caught
//
// caught:
// ret i32 1
// }
//
let try_func_ty = bx.type_func(&[bx.type_i8p()], bx.type_void());
bx.invoke(try_func_ty, None, None, try_func, &[data], normal, catchswitch, None);
bx.switch_to_block(normal);
bx.ret(bx.const_i32(0));
bx.switch_to_block(catchswitch);
let cs = bx.catch_switch(None, None, &[catchpad]);
bx.switch_to_block(catchpad);
let null = bx.const_null(bx.type_i8p());
let funclet = bx.catch_pad(cs, &[null]);
let ptr = bx.call_intrinsic("llvm.wasm.get.exception", &[funclet.cleanuppad()]);
let _sel = bx.call_intrinsic("llvm.wasm.get.ehselector", &[funclet.cleanuppad()]);
let catch_ty = bx.type_func(&[bx.type_i8p(), bx.type_i8p()], bx.type_void());
bx.call(catch_ty, None, None, catch_func, &[data, ptr], Some(&funclet));
bx.catch_ret(&funclet, caught);
bx.switch_to_block(caught);
bx.ret(bx.const_i32(1));
});
// Note that no invoke is used here because by definition this function
// can't panic (that's what it's catching).
let ret = bx.call(llty, None, None, llfn, &[try_func, data, catch_func], None);
let i32_align = bx.tcx().data_layout.i32_align.abi;
bx.store(ret, dest, i32_align);
}
// Definition of the standard `try` function for Rust using the GNU-like model
// of exceptions (e.g., the normal semantics of LLVM's `landingpad` and `invoke`
// instructions).