#9400: poor performance when compiling modules with many Text literals at -O1 -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Resolution: | Keywords: Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: Compile- | Blocked By: time performance bug | Related Tickets: #9370 Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Description changed by rwbarton: Old description:
(Spawned from #9370; see there for original discussion)
Unpack the xmlhtml package and edit `src/Text/XmlHtml/HTML/Meta.hs` and remove the `OPTIONS_GHC` line at the top of the file that disables optimizations and build with `cabal buidl`. Then GHC takes ~1.5GB and over a minute to build this single module.
Preliminary investigation indicates that Text's fromString and its constituent parts is being inlined repeatedly: {{{ Inlining done: Data.String.fromString Inlining done: Data.Text.$fIsStringText Inlining done: Data.Text.pack Inlining done: Data.Text.Internal.Fusion.unstream Inlining done: Data.Text.Internal.Fusion.Common.map Inlining done: Data.Text.Internal.Fusion.Common.streamList Inlining done: Data.Text.Internal.safe Inlining done: Data.Bits.$fBitsInt_$c.&. Inlining done: Data.Text.Internal.Fusion.Types.$WYield [ repeats ~4000 times ] }}} resulting in a very large intermediate program: {{{ *** Checking old interface for xmlhtml-0.2.3.2:Text.XmlHtml.HTML.Meta: [ 1 of 10] Compiling Text.XmlHtml.HTML.Meta ( src/Text/XmlHtml/HTML/Meta.hs, dist/build/Text/XmlHtml/HTML/Meta.o ) *** Parser: *** Renamer/typechecker: *** Desugar: Result size of Desugar (after optimization) = {terms: 26,260, types: 20,021, coercions: 0} *** Simplifier: Result size of Simplifier iteration=1 = {terms: 1,446,658, types: 953,432, coercions: 314,352} ... }}}
New description: (Spawned from #9370; see there for original discussion) Unpack the xmlhtml package and edit `src/Text/XmlHtml/HTML/Meta.hs` and remove the `OPTIONS_GHC` line at the top of the file that disables optimizations and build with `cabal buidl`. Then GHC takes ~1.5GB and over a minute to build this single module. Preliminary investigation indicates that Text's fromString and its constituent parts is being inlined repeatedly: {{{ Inlining done: Data.String.fromString Inlining done: Data.Text.$fIsStringText Inlining done: Data.Text.pack Inlining done: Data.Text.Internal.Fusion.unstream Inlining done: Data.Text.Internal.Fusion.Common.map Inlining done: Data.Text.Internal.Fusion.Common.streamList Inlining done: Data.Text.Internal.safe Inlining done: Data.Bits.$fBitsInt_$c.&. Inlining done: Data.Text.Internal.Fusion.Types.$WYield [ repeats ~4000 times ] }}} resulting in a very large intermediate program: {{{ [ 1 of 10] Compiling Text.XmlHtml.HTML.Meta ( src/Text/XmlHtml/HTML/Meta.hs, dist/build/Text/XmlHtml/HTML/Meta.o ) *** Parser: *** Renamer/typechecker: *** Desugar: Result size of Desugar (after optimization) = {terms: 26,806, types: 14,467, coercions: 0} *** Simplifier: Result size of Simplifier iteration=1 = {terms: 31,052, types: 20,719, coercions: 0} Result size of Simplifier = {terms: 31,052, types: 20,719, coercions: 0} *** Specialise: Result size of Specialise = {terms: 32,254, types: 22,696, coercions: 448} *** Float out(FOS {Lam = Just 0, Consts = True, PAPs = False}): Result size of Float out(FOS {Lam = Just 0, Consts = True, PAPs = False}) = {terms: 63,022, types: 59,045, coercions: 448} *** Float inwards: Result size of Float inwards = {terms: 63,022, types: 59,045, coercions: 448} *** Simplifier: Result size of Simplifier iteration=1 = {terms: 28,537, types: 18,902, coercions: 654} Result size of Simplifier iteration=2 = {terms: 28,157, types: 18,257, coercions: 152} Result size of Simplifier iteration=3 = {terms: 28,074, types: 18,128, coercions: 140} Result size of Simplifier iteration=4 = {terms: 28,068, types: 18,096, coercions: 61} Result size of Simplifier = {terms: 28,068, types: 18,096, coercions: 61} *** Simplifier: Result size of Simplifier iteration=1 = {terms: 43,941, types: 38,325, coercions: 61} Result size of Simplifier = {terms: 43,941, types: 38,325, coercions: 61} *** Simplifier: Result size of Simplifier iteration=1 = {terms: 689,670, types: 461,960, coercions: 146,725} ... }}} [Edited: old output was not actually for `-O1` as described, but rather for the sequence described in #9370 of building with `-O0` after building another module with `-O1`.] -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9400#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler