mikros/rust
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Check RUSTC_CTFE_BACKTRACE much less by generating fewer errors

Browse Source 
Before this change, `get_size_and_align()`  calls `get_fn_alloc()` *a
lot* in CTFE heavy code. This previously returned an `Error` which would
check if `RUSTC_CTFE_BACKTRACE` was set on construction. Doing this
turned out to be a performance hotspot as @nnethercote discovered in
#68792.

This is an alternate take on that PR which resolves the performance
issue by generating *many* fewer errors. Previously, `ctfe-stress-4`
would generate over 5,000,000 errors each of which would check for the
presence of the environment variable. With these changes, that number is
reduced to 30.
This commit is contained in:
Wesley Wiser 2020-02-19 07:59:21 -05:00
parent ae5467826d
commit 9f3bc82fe4
1 changed files with 6 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
src/librustc_mir/interpret/memory.rs
View File

@ -560,7 +560,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
// # Function pointers
// (both global from `alloc_map` and local from `extra_fn_ptr_map`)
if let Ok(_) = self.get_fn_alloc(id) {
if let Some(_) = self.get_fn_alloc(id) {
return if let AllocCheck::Dereferenceable = liveness {
// The caller requested no function pointers.
throw_unsup!(DerefFunctionPointer)
@ -602,14 +602,14 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
}
}
fn get_fn_alloc(&self, id: AllocId) -> InterpResult<'tcx, FnVal<'tcx, M::ExtraFnVal>> {
fn get_fn_alloc(&self, id: AllocId) -> Option<FnVal<'tcx, M::ExtraFnVal>> {
trace!("reading fn ptr: {}", id);
if let Some(extra) = self.extra_fn_ptr_map.get(&id) {
Ok(FnVal::Other(*extra))
Some(FnVal::Other(*extra))
} else {
match self.tcx.alloc_map.lock().get(id) {
Some(GlobalAlloc::Function(instance)) => Ok(FnVal::Instance(instance)),
_ => throw_unsup!(ExecuteMemory),
Some(GlobalAlloc::Function(instance)) => Some(FnVal::Instance(instance)),
_ => None,
}
}
}
@ -622,7 +622,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
if ptr.offset.bytes() != 0 {
throw_unsup!(InvalidFunctionPointer)
}
self.get_fn_alloc(ptr.alloc_id)
self.get_fn_alloc(ptr.alloc_id).ok_or_else(|| err_unsup!(ExecuteMemory).into())
}
pub fn mark_immutable(&mut self, id: AllocId) -> InterpResult<'tcx> {