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Auto merge of #109466 - davidlattimore:inline-arg-via-var-debug-info, r=wesleywiser

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Preserve argument indexes when inlining MIR

We store argument indexes on VarDebugInfo. Unlike the previous method of relying on the variable index to know whether a variable is an argument, this survives MIR inlining.

We also no longer check if var.source_info.scope is the outermost scope. When a function gets inlined, the arguments to the inner function will no longer be in the outermost scope. What we care about though is whether they were in the outermost scope prior to inlining, which we know by whether we assigned an argument index.

Fixes #83217

I considered using `Option<NonZeroU16>` instead of `Option<u16>` to store the index. I didn't because `TypeFoldable` isn't implemented for `NonZeroU16` and because it looks like due to padding, it currently wouldn't make any difference. But I indexed from 1 anyway because (a) it'll make it easier if later it becomes worthwhile to use a `NonZeroU16` and because the arguments were previously indexed from 1, so it made for a smaller change.

This is my first PR on rust-lang/rust, so apologies if I've gotten anything not quite right.
This commit is contained in:
bors 2023-04-13 01:51:27 +00:00
commit d8fc819247
8 changed files with 67 additions and 7 deletions
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10
compiler/rustc_codegen_ssa/src/mir/debuginfo.rs
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@ -442,11 +442,10 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
let (var_ty, var_kind) = match var.value {
mir::VarDebugInfoContents::Place(place) => {
let var_ty = self.monomorphized_place_ty(place.as_ref());
let var_kind = if self.mir.local_kind(place.local) == mir::LocalKind::Arg
let var_kind = if let Some(arg_index) = var.argument_index
&& place.projection.is_empty()
&& var.source_info.scope == mir::OUTERMOST_SOURCE_SCOPE
{
let arg_index = place.local.index() - 1;
let arg_index = arg_index as usize;
if target_is_msvc {
// ScalarPair parameters are spilled to the stack so they need to
// be marked as a `LocalVariable` for MSVC debuggers to visualize
@ -455,13 +454,12 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
if let Abi::ScalarPair(_, _) = var_ty_layout.abi {
VariableKind::LocalVariable
} else {
VariableKind::ArgumentVariable(arg_index + 1)
VariableKind::ArgumentVariable(arg_index)
}
} else {
// FIXME(eddyb) shouldn't `ArgumentVariable` indices be
// offset in closures to account for the hidden environment?
// Also, is this `+ 1` needed at all?
VariableKind::ArgumentVariable(arg_index + 1)
VariableKind::ArgumentVariable(arg_index)
}
} else {
VariableKind::LocalVariable