Rollup of 10 pull requests#159080
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Signed-off-by: Amirhossein Akhlaghpour <m9.akhlaghpoor@gmail.com>
For small repr(C) aggregates with padding, direct constant
initialization can still lower into field-wise construction plus
memcpy. That leaves the backend to rediscover that the whole object
is a single constant byte pattern.
This is especially visible for non-zero constant aggregates. Instead
of materializing them as separate field stores, we want codegen_ssa to
emit the packed value directly. For example, a value like
InnerPadded { a: 0, b: 1, c: 0 }
can otherwise lower to something like
store i16 0, ptr %val, align 4
store i8 1, ptr %val_plus_2, align 2
store i32 0, ptr %val_plus_4, align 4
call void @llvm.memcpy(..., ptr %val, ...)
while this change produces
store i64 65536, ptr %val, align 4
call void @llvm.memcpy(..., ptr %val, ...)
Why not solve this in LLVM?
At the problematic lowering point, rustc still knows that the MIR
aggregate is small and fully constant. LLVM only sees a lowered stack
temporary built from per-field stores and then copied out. Recovering
that packed constant there would require rediscovering front-end
aggregate semantics after lowering, so emitting the packed store in
rustc is the simpler and more local fix.
Why not keep the previous typed-copy approach?
An earlier approach zeroed padding on typed copies whose source could
be traced back to a constant assignment. That helped some cases, but it
also widened the optimization to runtime copy paths and could introduce
extra runtime stores purely to maintain padding knowledge. That is not
an acceptable tradeoff here.
Keep the scope narrow instead: only handle direct MIR aggregates whose
fields are all constants, and pack them according to the target
endianness before emitting a single integer store.
Add a focused codegen test covering the original PR 157690 entry
points together with non-zero constant cases. The test uses
-Cno-prepopulate-passes so it checks the immediate-store shape directly
at rustc codegen time, instead of depending on later LLVM store
merging.
Since PR 154149, when one item is glob-imported into a module twice with different visibilities, the first-arrived declaration stays in the resolution slot and the most visible declaration of the ambiguous glob set is only recorded in `ambiguity_vis_max`. `DeclData::vis()` returns the max, so name resolution, metadata reexports and `cross_crate_inlinable` export the item at the maximum visibility, but `set_bindings_effective_visibilities` walked only the slot-resident declaration's reexport chain. When the restricted route arrives first, the definition's effective visibility caps at the restricted visibility while the item is still exported: spurious dead_code, the item missing from reachable_set, should_encode_mir returning false, and downstream crates failing with "missing optimized MIR" (a 1.96.1 -> 1.97.0 stable-to-stable regression). Generalize the one-level `ambiguity_vis_max` update that PR 154149 added in `update_import` (to keep the most visible import from being reported as unused) into a walk of that declaration's whole reexport chain: extract the chain walk into `update_decl_chain` and recurse into `ambiguity_vis_max` at every hop, so the most visible declaration drives the effective visibility of everything on its route, including the final definition. Updates are monotone, so the dual walk is order-independent. The `ambiguous_import_visibilities` lint and the PR 156284 diagnostic suppression are untouched.
…alfJung codegen_ssa: pack small const aggregates into immediate stores Close rust-lang#157373 For small repr(C) aggregates with padding, direct constant initialization can still lower into field-wise construction plus memcpy. That leaves the backend to rediscover that the whole object is a single constant byte pattern. This is especially visible for non-zero constant aggregates. Instead of materializing them as separate field stores, we want codegen_ssa to emit the packed value directly. For example, a value like InnerPadded { a: 0, b: 1, c: 0 } can otherwise lower to something like store i16 0, ptr %val, align 4 store i8 1, ptr %val_plus_2, align 2 store i32 0, ptr %val_plus_4, align 4 call void @llvm.memcpy(..., ptr %val, ...) while this change produces store i64 65536, ptr %val, align 4 call void @llvm.memcpy(..., ptr %val, ...) Why not solve this in LLVM? At the problematic lowering point, rustc still knows that the MIR aggregate is small and fully constant. LLVM only sees a lowered stack temporary built from per-field stores and then copied out. Recovering that packed constant there would require rediscovering front-end aggregate semantics after lowering, so emitting the packed store in rustc is the simpler and more local fix. Why not keep the previous typed-copy approach? An earlier approach zeroed padding on typed copies whose source could be traced back to a constant assignment. That helped some cases, but it also widened the optimization to runtime copy paths and could introduce extra runtime stores purely to maintain padding knowledge. That is not an acceptable tradeoff here. Keep the scope narrow instead: only handle direct MIR aggregates whose fields are all constants, and pack them according to the target endianness before emitting a single integer store.
…pkin Deny `todo!()` in tidy Implements rust-lang/compiler-team#999 Part of rust-lang#158173
Use `as_lang_item` instead of repeatedly matching drive-by fix I noticed while reviewing https://github.com/rust-lang/rust/pull/157489/changes#r3550851573
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@bors r+ rollup=never p=5 |
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…uwer Rollup of 10 pull requests Successful merges: - #157690 (codegen_ssa: pack small const aggregates into immediate stores) - #157706 (Deny `todo!()` in tidy) - #159005 (Use `as_lang_item` instead of repeatedly matching) - #156735 (Move NativeLib::filename to the rmeta-link archive member) - #159039 (resolve: fix effective visibilities for items in ambiguous glob sets) - #158930 (Reorganize `tests/ui/issues` [20/N]) - #158965 (Add codegen test for Result is_ok unwrap) - #158979 (Reorganize `tests/ui/issues` [21/N]) - #159050 (assert only opaques with sub unified hidden infer are non-rigid) - #159062 (Remove unused WEAK_ONLY_LANG_ITEMS static) Failed merges: - #158732 (Apply MCP 1003 and move diagnostics.rs into its own module)
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The job Click to see the possible cause of the failure (guessed by this bot) |
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💔 Test for dd442ab failed: CI. Failed job:
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PR #157706, which is a member of this rollup, was unapproved. |
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Successful merges:
todo!()in tidy #157706 (Denytodo!()in tidy)as_lang_iteminstead of repeatedly matching #159005 (Useas_lang_iteminstead of repeatedly matching)tests/ui/issues[20/N] #158930 (Reorganizetests/ui/issues[20/N])tests/ui/issues[21/N] #158979 (Reorganizetests/ui/issues[21/N])Failed merges:
r? @ghost
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