Improve canonicalization performance by introducing `TypingMode::ErasedNotCoherence` by jdonszelmann · Pull Request #155443 · rust-lang/rust

jdonszelmann · 2026-04-17T14:18:41Z

This introduces TypingMode::ErasedNotCoherence. Most typing modes contain a list of opaque types, which are quite often unused during canonicalization. With this change, any time we try canonicalization, we replace whichever typing mode we're currently in with ErasedNotcoherence, attempt to canonicalize, and if that fails retry in the original typing mode. If erased mode succeeds, this is beneficial because that way the opaque types don't end up in the cache key, allowing more cache reuse.

This seems to have a small (0.5%) slowdown on most programs, but a dramatic (>60%) speedup in specific cases like the rustc-perf wg-grammar benchmark. Some more improvements are expected with "eager normalization", which is work that's under way right now.

jdonszelmann · 2026-04-17T14:18:48Z

@bors try

jdonszelmann · 2026-04-17T14:21:04Z

@bors try parent=14196dbfa3eb7c30195251eac092b1b86c8a2d84

[DO NOT MERGE] Improve canonicalization performance

jdonszelmann · 2026-04-17T14:21:23Z

@rust-timer queue

rust-bors · 2026-04-17T16:27:41Z

☀️ Try build successful (CI)
Build commit: db1df07 (db1df07682e37be559858ab003b949a2c17b5b3b, parent: 14196dbfa3eb7c30195251eac092b1b86c8a2d84)

rust-timer · 2026-04-17T17:34:03Z

Finished benchmarking commit (db1df07): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.8%	[0.2%, 1.8%]	11
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.6%	[-1.0%, -0.2%]	2
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary -0.9%, secondary 1.7%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	1.1%	[1.1%, 1.1%]	1
Regressions ❌ (secondary)	1.7%	[1.0%, 2.6%]	7
Improvements ✅ (primary)	-2.8%	[-2.8%, -2.8%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.9%	[-2.8%, 1.1%]	2

Cycles

Results (primary -2.4%, secondary 28.5%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	28.5%	[28.5%, 28.5%]	1
Improvements ✅ (primary)	-2.4%	[-2.4%, -2.4%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.4%	[-2.4%, -2.4%]	1

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 491.114s -> 492.029s (0.19%)
Artifact size: 394.23 MiB -> 394.80 MiB (0.14%)

rustbot · 2026-04-28T08:12:29Z

changes to the core type system

cc @lcnr

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri

…d-not-coherence

rust-log-analyzer · 2026-04-28T13:38:29Z

The job x86_64-gnu-gcc failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

---- [run-make] tests/run-make-cargo/rustc-crates-on-stable stdout ----

error: rmake recipe failed to complete
status: exit status: 1
command: cd "/checkout/obj/build/x86_64-unknown-linux-gnu/test/run-make-cargo/rustc-crates-on-stable/rmake_out" && env -u RUSTFLAGS -u __RUSTC_DEBUG_ASSERTIONS_ENABLED -u __STD_DEBUG_ASSERTIONS_ENABLED -u __STD_REMAP_DEBUGINFO_ENABLED AR="ar" BUILD_ROOT="/checkout/obj/build/x86_64-unknown-linux-gnu" CARGO="/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools-bin/cargo" CC="cc" CC_DEFAULT_FLAGS="-ffunction-sections -fdata-sections -fPIC -m64" CXX="c++" CXX_DEFAULT_FLAGS="-ffunction-sections -fdata-sections -fPIC -m64" HOST_RUSTC_DYLIB_PATH="/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" LD_LIBRARY_PATH="/checkout/obj/build/x86_64-unknown-linux-gnu/bootstrap-tools/x86_64-unknown-linux-gnu/release/deps:/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" LD_LIB_PATH_ENVVAR="LD_LIBRARY_PATH" LLVM_BIN_DIR="/checkout/obj/build/x86_64-unknown-linux-gnu/ci-llvm/bin" LLVM_COMPONENTS="aarch64 aarch64asmparser aarch64codegen aarch64desc aarch64disassembler aarch64info aarch64utils abi aggressiveinstcombine all all-targets amdgpu amdgpuasmparser amdgpucodegen amdgpudesc amdgpudisassembler amdgpuinfo amdgputargetmca amdgpuutils analysis arm armasmparser armcodegen armdesc armdisassembler arminfo armutils asmparser asmprinter avr avrasmparser avrcodegen avrdesc avrdisassembler avrinfo binaryformat bitreader bitstreamreader bitwriter bpf bpfasmparser bpfcodegen bpfdesc bpfdisassembler bpfinfo cas cfguard cgdata codegen codegentypes core coroutines coverage csky cskyasmparser cskycodegen cskydesc cskydisassembler cskyinfo debuginfobtf debuginfocodeview debuginfodwarf debuginfodwarflowlevel debuginfogsym debuginfologicalview debuginfomsf debuginfopdb demangle dlltooldriver dtlto dwarfcfichecker dwarflinker dwarflinkerclassic dwarflinkerparallel dwp engine executionengine extensions filecheck frontendatomic frontenddirective frontenddriver frontendhlsl frontendoffloading frontendopenacc frontendopenmp fuzzercli fuzzmutate globalisel hexagon hexagonasmparser hexagoncodegen hexagondesc hexagondisassembler hexagoninfo hipstdpar instcombine instrumentation interfacestub interpreter ipo irprinter irreader jitlink libdriver lineeditor linker loongarch loongarchasmparser loongarchcodegen loongarchdesc loongarchdisassembler loongarchinfo lto m68k m68kasmparser m68kcodegen m68kdesc m68kdisassembler m68kinfo mc mca mcdisassembler mcjit mcparser mips mipsasmparser mipscodegen mipsdesc mipsdisassembler mipsinfo mirparser msp430 msp430asmparser msp430codegen msp430desc msp430disassembler msp430info native nativecodegen nvptx nvptxcodegen nvptxdesc nvptxinfo objcarcopts objcopy object objectyaml option orcdebugging orcjit orcshared orctargetprocess passes plugins powerpc powerpcasmparser powerpccodegen powerpcdesc powerpcdisassembler powerpcinfo profiledata remarks riscv riscvasmparser riscvcodegen riscvdesc riscvdisassembler riscvinfo riscvtargetmca runtimedyld sandboxir scalaropts selectiondag sparc sparcasmparser sparccodegen sparcdesc sparcdisassembler sparcinfo support supportlsp symbolize systemz systemzasmparser systemzcodegen systemzdesc systemzdisassembler systemzinfo tablegen target targetparser telemetry textapi textapibinaryreader transformutils vectorize webassembly webassemblyasmparser webassemblycodegen webassemblydesc webassemblydisassembler webassemblyinfo webassemblyutils windowsdriver windowsmanifest x86 x86asmparser x86codegen x86desc x86disassembler x86info x86targetmca xray xtensa xtensaasmparser xtensacodegen xtensadesc xtensadisassembler xtensainfo" LLVM_FILECHECK="/checkout/obj/build/x86_64-unknown-linux-gnu/ci-llvm/bin/FileCheck" PYTHON="/usr/bin/python3" RUSTC="/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" RUSTDOC="/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustdoc" SOURCE_ROOT="/checkout" TARGET="x86_64-unknown-linux-gnu" TARGET_EXE_DYLIB_PATH="/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" __BOOTSTRAP_JOBS="4" __RMAKE_VERBOSE_SUBPROCESS_OUTPUT="1" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/run-make-cargo/rustc-crates-on-stable/rmake"
stdout: none
--- stderr -------------------------------
command failed at line 41
LD_LIBRARY_PATH="/checkout/obj/build/x86_64-unknown-linux-gnu/test/run-make-cargo/rustc-crates-on-stable/rmake_out:/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib:/checkout/obj/build/x86_64-unknown-linux-gnu/bootstrap-tools/x86_64-unknown-linux-gnu/release/deps:/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" RUSTC="/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" RUSTC_STAGE="0" RUSTFLAGS="-Zallow-features=" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools-bin/cargo" "build" "--manifest-path" "/checkout/Cargo.toml" "--no-default-features" "--target-dir" "target" "-p" "rustc_type_ir" "-p" "rustc_next_trait_solver" "-p" "rustc_pattern_analysis" "-p" "rustc_lexer" "-p" "rustc_abi" "-p" "rustc_parse_format" "-p" "rustc_hashes"
output status: `exit status: 101`
=== STDOUT ===



=== STDERR ===
    Blocking waiting for file lock on package cache
---

error: cannot find derive macro `GenericTypeVisitable` in this scope
##[error]   --> compiler/rustc_type_ir/src/solve/mod.rs:318:33
    |
318 | #[derive(TypeVisitable_Generic, GenericTypeVisitable, TypeFoldable_Generic, Lift_Generic)]
    |                                 ^^^^^^^^^^^^^^^^^^^^
    |
help: consider importing one of these derive macros
    |
  3 + use crate::GenericTypeVisitable;

For more information how to resolve CI failures of this job, visit this link.

rust-bors · 2026-04-29T08:01:15Z

☔ The latest upstream changes (presumably #155953) made this pull request unmergeable. Please resolve the merge conflicts.

lcnr · 2026-04-29T08:36:26Z

+            // If we get here in erased mode, we don't know the original typing mode.
+            // It could be post analysis, or something else.
+            // Regardless of what it was, we want to continue in erased mode,
+            // if we end up accessing any opaque types we bail out anyway.
+            | TypingMode::ErasedNotCoherence(MayBeErased) => return self,


not too happy about this, want to get back to this

View changes since the review

lcnr · 2026-04-29T10:45:12Z

+                    self.opaque_accesses
+                        .rerun_if_in_post_analysis("normalize opaque type non local");
+                }
+                if self.opaque_accesses.should_bail() {


canfn rerun_if_in_post_analysis just return a Result<(), ShouldBail> or what not so we don't have to manually call should_bail afterwards

View changes since the review

lcnr · 2026-04-29T10:49:34Z

@@ -71,7 +71,13 @@ impl<'tcx> rustc_next_trait_solver::delegate::SolverDelegate for SolverDelegate<
                // FIXME: Properly consider opaques here.
                && self.inner.borrow_mut().opaque_types().is_empty()


maybe have a self.known_no_opaque_types_in_storage which returns false if typng mode is erased?

View changes since the review

then we still should return None though right? Cause we can keep the fast path

rustbot assigned lcnr Apr 17, 2026

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rust-bors Bot pushed a commit that referenced this pull request Apr 17, 2026

Auto merge of #155443 - jdonszelmann:canonical, r=<try>

db1df07

[DO NOT MERGE] Improve canonicalization performance

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 17, 2026

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rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Apr 17, 2026

jdonszelmann added 2 commits April 28, 2026 09:58

Add AccessedOpaques, tracking opaque access during canonicalization

443bb10

Change sg apis to cache opaque accesses

492571e

jdonszelmann force-pushed the canonical branch from a728352 to 22e7a5a Compare April 28, 2026 08:12

jdonszelmann marked this pull request as ready for review April 28, 2026 08:12

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 28, 2026

rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Apr 28, 2026

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jdonszelmann force-pushed the canonical branch from 22e7a5a to 407109f Compare April 28, 2026 08:39

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jdonszelmann force-pushed the canonical branch from 407109f to 2be0651 Compare April 28, 2026 08:58

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jdonszelmann force-pushed the canonical branch from 2be0651 to b7fcc19 Compare April 28, 2026 09:59

jdonszelmann changed the title ~~[DO NOT MERGE] Improve canonicalization performance~~ Improve canonicalization performance by introducing TypingMode::ErasedNotCoherence Apr 28, 2026

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jdonszelmann added 6 commits April 28, 2026 13:26

Introduced ErasedNotCoherence typing mode

cdc1c0d

type safety for typing mode outside trait solver which can't be erase…

2e5e2aa

…d-not-coherence

Add logging in various places

d90cd64

Try to canonicalize with erased opaques, retry when opaques are used.

c480970

Refactor fetch_eligible_assoc_item output

c5f1587

consistently return OpaquesAccessed from probes to signal why they error

58e27a3

jdonszelmann force-pushed the canonical branch from b7fcc19 to ed648ca Compare April 28, 2026 11:29

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some attempts at improving coroutines resulting in FIXME

cf0435a

jdonszelmann force-pushed the canonical branch from ed648ca to cf0435a Compare April 28, 2026 12:42

		@@ -71,7 +71,13 @@ impl<'tcx> rustc_next_trait_solver::delegate::SolverDelegate for SolverDelegate<
		// FIXME: Properly consider opaques here.
		&& self.inner.borrow_mut().opaque_types().is_empty()

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rust-timer commented Apr 17, 2026

Overall result: ❌✅ regressions and improvements - please read:

Instruction count

Max RSS (memory usage)

Cycles

Binary size

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