[GHC] #14944: Compile speed regression
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Compile time went from 5 seconds in 7.6.1 to 12 seconds in 8.2.2 and then down to 10 seconds in 8.4.1. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by br1): * Attachment "Main.hs" added. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by br1): * Attachment "Paper.hs" added. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Description changed by br1: Old description:
Compile time went from 5 seconds in 7.6.1 to 12 seconds in 8.2.2 and then down to 10 seconds in 8.4.1.
New description: Compile time with -O went from 5 seconds in 7.6.1 to 12 seconds in 8.2.2 and then down to 10 seconds in 8.4.1. -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * owner: (none) => dfeuer Comment: David will characterise this. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression
-------------------------------------+-------------------------------------
Reporter: br1 | Owner: dfeuer
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 8.4.1
Resolution: | Keywords:
Operating System: Unknown/Multiple | Architecture:
Type of failure: Compile-time | Unknown/Multiple
performance bug | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s):
Wiki Page: |
-------------------------------------+-------------------------------------
Comment (by dfeuer):
The reason for the big version gap seems likely to be the fact that the
code didn't compile at all under 7.8.4 or 7.10.3 without extra help. Here
are the times I get:
=== 7.8.4
This version needed `-fcontext-stack=197` to compile.
<
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Does the size of the program change at all between 7.6 and 8.4? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): I'm looking into that new. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): Yes, the size of the program changes quite a lot. The most notable thing about this program is the sheer number of types, which is enormous in every case, but varies quite a lot. In each case I give the result of `CorePrep` from `Paper` (which always compiles reasonably quickly) along with pertinent-looking information about `Main` (which takes a while). === 7.8.4 Paper: {{{ {terms: 1,719, types: 4,049, coercions: 768} }}} Main: {{{ Result size of Desugar (after optimization) = {terms: 3,973, types: 630,023, coercions: 196} ... Result size of Simplifier = {terms: 3,384, types: 628,456, coercions: 5} Result size of Specialise = {terms: 4,785, types: 865,456, coercions: 5} Result size of Float out(FOS {Lam = Just 0, Consts = True, PAPs = False}) = {terms: 6,373, types: 1,100,676, coercions: 5} Result size of Simplifier iteration=1 = {terms: 8,674, types: 1,377,245, coercions: 211,797} Result size of Simplifier iteration=2 = {terms: 4,051, types: 730,227, coercions: 84,460} -- things go up and down a few times Result size of Tidy Core = {terms: 5,157, types: 1,104,496, coercions: 84,451} }}} === 7.10.3 Paper: {{{ Result size of CorePrep = {terms: 1,736, types: 3,973, coercions: 778} }}} Main: {{{ Result size of Desugar (after optimization) = {terms: 3,973, types: 630,023, coercions: 196} Result size of Specialise = {terms: 12,088, types: 2,092,764, coercions: 392} *** Float out(FOS {Lam = Just 0, Consts = True, OverSatApps = False}): Result size of Float out(FOS {Lam = Just 0, Consts = True, OverSatApps = False}) = {terms: 13,674, types: 2,327,982, coercions: 392} Result size of Simplifier iteration=1 = {terms: 14,824, types: 2,416,989, coercions: 371,022} Result size of Simplifier iteration=2 = {terms: 10,101, types: 2,096,313, coercions: 321,082} Result size of Simplifier iteration=1 = {terms: 12,295, types: 2,650,706, coercions: 321,081} ... nothing much changes for a long time -- Sudden size drop in core tidy Result size of Tidy Core = {terms: 5,146, types: 1,104,452, coercions: 84,448} }}} This comment is getting long; I'll continue in the next one. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): === 8.0.2 Paper: {{{ Result size of CorePrep = {terms: 2,704, types: 5,400, coercions: 996} }}} Main: {{{ Result size of Desugar (after optimization) = {terms: 4,574, types: 632,608, coercions: 196} Result size of Specialise = {terms: 13,274, types: 2,100,628, coercions: 392} Result size of Float out(FOS {Lam = Just 0, Consts = True, OverSatApps = False}) = {terms: 14,860, types: 2,335,846, coercions: 392} Result size of Simplifier iteration=1 = {terms: 15,614, types: 2,423,788, coercions: 366,704} Result size of Simplifier iteration=2 = {terms: 10,121, types: 2,098,814, coercions: 322,579} .... Result size of Simplifier = {terms: 12,570, types: 2,807,500, coercions: 320,217} Result size of Tidy Core = {terms: 5,208, types: 1,104,414, coercions: 84,359} }}} === 8.2.2 Paper: {{{ Result size of CorePrep = {terms: 3,280, types: 5,538, coercions: 1,000, joins: 2/50} }}} Main: {{{ Result size of Desugar (after optimization) = {terms: 4,564, types: 632,574, coercions: 196, joins: 0/982} Result size of Simplifier iteration=1 = {terms: 6,858, types: 1,023,896, coercions: 86,509, joins: 0/786} Result size of Simplifier iteration=2 = {terms: 4,014, types: 726,796, coercions: 85,137, joins: 1/2} ... Result size of Specialise = {terms: 9,329, types: 1,646,724, coercions: 168,346, joins: 2/2} *** Float out(FOS {Lam = Just 0, Consts = True, OverSatApps = False}) [Main]: Result size of Float out(FOS {Lam = Just 0, Consts = True, OverSatApps = False}) = {terms: 10,823, types: 1,939,926, coercions: 168,346, joins: 1/2} Result size of Simplifier iteration=1 = {terms: 9,648, types: 1,706,501, coercions: 227,811, joins: 2/2} Result size of Simplifier iteration=2 = {terms: 9,349, types: 1,647,213, coercions: 168,353, joins: 2/2} ... Result size of Tidy Core = {terms: 5,212, types: 1,104,424, coercions: 84,359, joins: 2/2} }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): === 8.4.1 Paper: {{{ Result size of CorePrep = {terms: 3,228, types: 5,423, coercions: 1,008, joins: 3/50} }}} Main: {{{ Result size of Desugar (after optimization) = {terms: 4,564, types: 632,574, coercions: 196, joins: 0/982} Result size of Simplifier iteration=1 = {terms: 6,858, types: 1,023,896, coercions: 86,509, joins: 0/786} Result size of Simplifier iteration=2 = {terms: 4,014, types: 726,796, coercions: 85,137, joins: 1/2} Result size of Specialise = {terms: 9,329, types: 1,646,724, coercions: 168,346, joins: 2/2} Result size of Float out(FOS {Lam = Just 0, Consts = True, OverSatApps = False}) = {terms: 10,431, types: 1,862,310, coercions: 168,346, joins: 1/2} Result size of Simplifier iteration=1 = {terms: 9,648, types: 1,706,501, coercions: 227,811, joins: 2/2} Result size of Simplifier iteration=2 = {terms: 9,349, types: 1,647,213, coercions: 168,353, joins: 2/2} ... Result size of Simplifier = {terms: 9,334, types: 1,647,199, coercions: 168,352, joins: 2/2} -- What happened here?????? Result size of Simplifier iteration=1 = {terms: 110,206, types: 1,818,532, coercions: 379,933, joins: 593/20,293} Result size of Simplifier = {terms: 8,914, types: 1,272,932, coercions: 85,550, joins: 5/203} .... Result size of Demand analysis = {terms: 8,323, types: 1,272,755, coercions: 85,550, joins: 5/6} !!! Demand analysis [Main]: finished in 200.01 milliseconds, allocated 115.130 megabytes *** CoreTidy [Main]: Result size of Tidy Core = {terms: 1,867, types: 166,695, coercions: 1,988, joins: 5/6} }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Thanks for this data. Several interesting things here. * There's a big jump in compilation cost between 7.8 and 7.10. (Like a factor of 2 in compiler allocation, according to comment:3. According to comment:6, the result of Specialise is much bigger in 7.10 than in 7.8. This extra code appears to be discarded at the end, but it persists through the compilation pipeline. '''Questions''': what are the extra specialisations? Do we need them? Why are they eventually discarded? Could we discard them earlier? * As you say in comment:8 it seems that GHC 8.4 has a new, and huge (temporary) blow-up in porgram size. It'd be really good to work out what this is. (You'll presumably need to cut down the program size to make this tractable.) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): In case this helps any, the simplifier runs iteration 1,2,1,2,3,1,2,3, and then the next iteration (1) is the one that blows up the term count in 8.4.1. It appears that the blow-up is non-linear. When I increase the number of lines in the `Main.hs` source, the ratio of terms in that iteration to terms in the previous one increases. Similarly, the ratio of time and allocation in that simplifier run compared to the previous one increases. I've tried looking at a very cut-down version with `-ddump- simpl-iterations`, but there are still an awful lot of terms to look at. I'll keep at it. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): Running with a development build of either 8.2.2 or 8.4ish (I haven't checked others yet) turns up an interesting warning when compiling `Paper.hs`: the simplifier bails out after 4 iterations. So it seems at least ''possible'' that whatever goes wrong in `Main.hs` may start in `Paper.hs`, if we end up with incompletely simplified unfoldings. One problem I'm facing is that this source code is ... not very simple. It's full of rather involved constraint-based programming that's presumably documented in a paper somewhere. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by br1): @dfeuer Here's the paper https://www.fing.edu.uy/~mviera/papers/pepm13.pdf -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): Simon suggests `-dshow-passes` comparing iterations in different GHC versions. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): Get back to bullet 1 of comment 9! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:14 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by dfeuer): * Attachment "passes-7.8" added. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by dfeuer): * Attachment "passes-7.10" added. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by dfeuer): * Attachment "passes-7.8" added. ghc -O -dshow-passes -fforce-recomp -fcontext-stack=400 Main.hs -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by dfeuer): * Attachment "passes-7.10" added. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by dfeuer): * Attachment "passes-8.0" added. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by dfeuer): * Attachment "passes-8.2" added. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by dfeuer): * Attachment "passes-8.4" added. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by dfeuer): * Attachment "passes-7.8-redacted" added. 7.8 passes with CPSZ lines removed -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): I'm going to attach `-v` results too, so we can look at how many simplifier passes were used. Is there a way to find out when the simplifier bailed out without a debug build? I don't really know how to get a debug build of 7.8. Building 7.8 with 7.8 didn't work, and I don't have 7.6 lying around. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:15 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): In 7.8, Main starts compiling like this (from -dshow-passes): {{{ Result size of Desugar (after optimization) = {terms: 3,973, types: 630,023, coercions: 196} *** Simplifier: Result size of Simplifier iteration=1 = {terms: 3,384, types: 628,452, coercions: 5} Result size of Simplifier iteration=2 = {terms: 3,386, types: 628,458, coercions: 5} Result size of Simplifier iteration=3 = {terms: 3,384, types: 628,456, coercions: 5} Result size of Simplifier = {terms: 3,384, types: 628,456, coercions: 5} *** Specialise: Result size of Specialise = {terms: 4,785, types: 865,456, coercions: 5} }}} In 7.10, on the other hand, it starts like this: {{{ Result size of Desugar (after optimization) = {terms: 3,973, types: 630,023, coercions: 196} *** Simplifier: Result size of Simplifier iteration=1 = {terms: 4,362, types: 630,802, coercions: 196} Result size of Simplifier = {terms: 4,362, types: 630,802, coercions: 196} *** Specialise: Result size of Specialise = {terms: 12,088, types: 2,092,764, coercions: 392} }}} So 7.8 immediately tossed a slew of coercions in the first simplifier iteration, and the simplification otherwise kept sizes pretty much the same. In 7.10, we only do one round of simplification, the coercion count doesn't go down, the term count goes up a bit, and then specialization goes wild. No, I don't know what any of this really means. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:16 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
participants (1)
-
GHC