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Implement constant propagation on top of MIR SSA analysis #116012

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merged 6 commits into from
Dec 30, 2023
Merged

Implement constant propagation on top of MIR SSA analysis #116012

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a03c972
Enable GVN by default.
cjgillot May 21, 2023
2837727
Replace legacy ConstProp by GVN.
cjgillot Sep 20, 2023
75e0824
Bless incremental tests.
cjgillot Jul 19, 2023
6dfda0d
Revert codegen test change.
cjgillot Dec 10, 2023
aa99688
Disable opt in incremental test.
cjgillot Dec 22, 2023
6d7f063
Avoid stack overflow in generalizer.
cjgillot Dec 24, 2023
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5 changes: 4 additions & 1 deletion compiler/rustc_infer/src/infer/relate/generalize.rs
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
use std::mem;

use rustc_data_structures::sso::SsoHashMap;
use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_hir::def_id::DefId;
use rustc_middle::infer::unify_key::{ConstVarValue, ConstVariableValue};
use rustc_middle::ty::error::TypeError;
Expand Down Expand Up @@ -226,7 +227,9 @@ where
let old_ambient_variance = self.ambient_variance;
self.ambient_variance = self.ambient_variance.xform(variance);
debug!(?self.ambient_variance, "new ambient variance");
let r = self.relate(a, b)?;
// Recursive calls to `relate` can overflow the stack. For example a deeper version of
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Could you put this onto the top generalizer relate call, in generalize? Or is the stack overflow due to a really deep type being generated?

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This is a really deep type.

I'm a bit guessing what the stack trace from CI points to. The failing test uses a deep type, and by making it even deeper I got a backtrace pointing involving this recursion.

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Discussed this offline. I guess this ensure_sufficient_stack invocation is fine.

// `ui/associated-consts/issue-93775.rs`.
let r = ensure_sufficient_stack(|| self.relate(a, b))?;
self.ambient_variance = old_ambient_variance;
Ok(r)
}
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