T0b1/wasmtime
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Mark loads from globals aligned and notrap.

Browse Source 
Mark loads from globals generated by cton_wasm or by legalization as
`aligned` and `notrap`, since memory for these globals should be
allocated by the runtime environment for that purpose. This reduces
the number of potentially trapping instructions, which can reduce
the amount of metadata required by embedding environments.
This commit is contained in:
Dan Gohman
2018-03-23 13:34:40 -07:00
parent bcd3309c15
commit 685cde98a4
9 changed files with 47 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
lib/wasm/src/code_translator.rs
View File

@@ -75,8 +75,9 @@ pub fn translate_operator<FE: FuncEnvironment + ?Sized>(
GlobalValue::Const(val) => val,
GlobalValue::Memory { gv, ty } => {
let addr = builder.ins().global_addr(environ.native_pointer(), gv);
// TODO: It is likely safe to set `aligned notrap` flags on a global load.
let flags = ir::MemFlags::new();
let mut flags = ir::MemFlags::new();
flags.set_notrap();
flags.set_aligned();
builder.ins().load(ty, flags, addr, 0)
}
};
@@ -87,8 +88,9 @@ pub fn translate_operator<FE: FuncEnvironment + ?Sized>(
GlobalValue::Const(_) => panic!("global #{} is a constant", global_index),
GlobalValue::Memory { gv, .. } => {
let addr = builder.ins().global_addr(environ.native_pointer(), gv);
// TODO: It is likely safe to set `aligned notrap` flags on a global store.
let flags = ir::MemFlags::new();
let mut flags = ir::MemFlags::new();
flags.set_notrap();
flags.set_aligned();
let val = state.pop1();
builder.ins().store(flags, val, addr, 0);
}
@@ -992,6 +994,9 @@ fn translate_load<FE: FuncEnvironment + ?Sized>(
// We don't yet support multiple linear memories.
let heap = state.get_heap(builder.func, 0, environ);
let (base, offset) = get_heap_addr(heap, addr32, offset, environ.native_pointer(), builder);
// Note that we don't set `is_aligned` here, even if the load instruction's
// alignment immediate says it's aligned, because WebAssembly's immediate
// field is just a hint, while Cretonne's aligned flag needs a guarantee.
let flags = MemFlags::new();
let (load, dfg) = builder.ins().Load(
opcode,
@@ -1017,6 +1022,7 @@ fn translate_store<FE: FuncEnvironment + ?Sized>(
// We don't yet support multiple linear memories.
let heap = state.get_heap(builder.func, 0, environ);
let (base, offset) = get_heap_addr(heap, addr32, offset, environ.native_pointer(), builder);
// See the comments in `translate_load` about the flags.
let flags = MemFlags::new();
builder.ins().Store(
opcode,