40% of time is spent in phase_4_translate_to_llvm during --crate-type bin --emit=dep-info,metadata #38964

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1. brson

   added

   I-slowIssue: Problems and improvements with respect to performance of generated code.Issue: Problems and improvements with respect to performance of generated code.

   T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

   I-compiletimeIssue: Problems and improvements with respect to compile times.Issue: Problems and improvements with respect to compile times.

   and removed

   I-slowIssue: Problems and improvements with respect to performance of generated code.Issue: Problems and improvements with respect to performance of generated code.

   on Jan 10, 2017
2. nrc commented on Jan 12, 2017

   

   nrc

   on Jan 12, 2017

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   -Ztime-passes:

   time: 0.030; rss: 38MB	parsing
   time: 0.000; rss: 38MB	recursion limit
   time: 0.000; rss: 38MB	crate injection
   time: 0.000; rss: 38MB	plugin loading
   time: 0.000; rss: 38MB	plugin registration
   time: 0.150; rss: 106MB	expansion
   time: 0.000; rss: 106MB	maybe building test harness
   time: 0.000; rss: 106MB	maybe creating a macro crate
   time: 0.000; rss: 106MB	checking for inline asm in case the target doesn't support it
   time: 0.001; rss: 106MB	complete gated feature checking
   time: 0.001; rss: 106MB	early lint checks
   time: 0.000; rss: 106MB	AST validation
   time: 0.017; rss: 111MB	name resolution
   time: 0.005; rss: 115MB	lowering ast -> hir
   time: 0.001; rss: 115MB	indexing hir
   time: 0.000; rss: 115MB	attribute checking
   time: 0.001; rss: 115MB	language item collection
   time: 0.001; rss: 115MB	lifetime resolution
   time: 0.000; rss: 115MB	looking for entry point
   time: 0.000; rss: 115MB	looking for plugin registrar
   time: 0.002; rss: 115MB	region resolution
   time: 0.000; rss: 115MB	loop checking
   time: 0.000; rss: 115MB	static item recursion checking
   time: 0.014; rss: 115MB	compute_incremental_hashes_map
   time: 0.000; rss: 115MB	load_dep_graph
   time: 0.000; rss: 115MB	stability index
   time: 0.002; rss: 115MB	stability checking
   time: 0.003; rss: 115MB	type collecting
   time: 0.000; rss: 115MB	variance inference
   time: 0.000; rss: 115MB	impl wf inference
   time: 0.018; rss: 128MB	coherence checking
   time: 0.011; rss: 128MB	wf checking
   time: 0.010; rss: 131MB	item-types checking
   time: 0.286; rss: 142MB	item-bodies checking
   time: 0.000; rss: 142MB	drop-impl checking
   time: 0.012; rss: 142MB	const checking
   time: 0.001; rss: 142MB	privacy checking
   time: 0.001; rss: 142MB	intrinsic checking
   time: 0.000; rss: 142MB	effect checking
   time: 0.005; rss: 142MB	match checking
   time: 0.002; rss: 143MB	liveness checking
   time: 0.007; rss: 143MB	rvalue checking
   time: 0.023; rss: 150MB	MIR dump
     time: 0.002; rss: 150MB	SimplifyCfg
     time: 0.004; rss: 150MB	QualifyAndPromoteConstants
     time: 0.006; rss: 150MB	TypeckMir
     time: 0.000; rss: 150MB	SimplifyBranches
     time: 0.001; rss: 150MB	SimplifyCfg
   time: 0.014; rss: 150MB	MIR cleanup and validation
   time: 0.026; rss: 151MB	borrow checking
   time: 0.000; rss: 151MB	reachability checking
   time: 0.001; rss: 151MB	death checking
   time: 0.000; rss: 151MB	unused lib feature checking
   time: 0.018; rss: 151MB	lint checking
   time: 0.000; rss: 151MB	resolving dependency formats
     time: 0.000; rss: 151MB	NoLandingPads
     time: 0.001; rss: 151MB	SimplifyCfg
     time: 0.003; rss: 151MB	EraseRegions
     time: 0.001; rss: 151MB	AddCallGuards
     time: 0.011; rss: 152MB	ElaborateDrops
     time: 0.000; rss: 152MB	NoLandingPads
     time: 0.002; rss: 152MB	SimplifyCfg
     time: 0.001; rss: 152MB	InstCombine
     time: 0.000; rss: 152MB	Deaggregator
     time: 0.000; rss: 152MB	CopyPropagation
     time: 0.001; rss: 152MB	SimplifyLocals
     time: 0.001; rss: 152MB	AddCallGuards
     time: 0.000; rss: 152MB	PreTrans
   time: 0.023; rss: 152MB	MIR optimisations
     time: 0.000; rss: 152MB	write metadata
     time: 0.451; rss: 200MB	translation item collection
     time: 0.051; rss: 207MB	codegen unit partitioning
   time: 0.759; rss: 207MB	translation
   time: 0.000; rss: 207MB	assert dep graph
   time: 0.000; rss: 207MB	serialize dep graph
     time: 0.000; rss: 207MB	llvm function passes [0]
     time: 0.000; rss: 207MB	llvm module passes [0]
     time: 0.000; rss: 207MB	codegen passes [0]
     time: 0.001; rss: 207MB	codegen passes [0]
   time: 0.002; rss: 207MB	LLVM passes
   time: 0.000; rss: 207MB	serialize work products
   time: 0.000; rss: 207MB	linking
   

   Investigating this, we branch to stop translating here: https://github.com/rust-lang/rust/blob/master/src/librustc_trans/base.rs#L1189

   But we're actually doing quite a lot of work before that, mostly it seems to construct modules. We ought to be able to skip some (hopefully most) of this work. @michaelwoerister has volunteered to try and make that work (thanks!).
3. michaelwoerister

   self-assigned this

   on Jan 12, 2017
4. michaelwoerister commented on Jan 12, 2017

   

   michaelwoerister

   on Jan 12, 2017

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   Yes, I'll look into it. There should be no reason to continue with trans after metadata has been written.
5. bors

   closed this as completedin #39184on Jan 21, 2017