[GHC] #10064: Add support for "foo"## literals to MagicHash
#10064: Add support for "foo"## literals to MagicHash -------------------------------------+------------------------------------- Reporter: chadaustin | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.8.4 Component: Compiler | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- I'm working on a high-performance library for building up buffers of data. Appending ByteStrings works pretty well, but, for bytestring literals, it's faster to avoid the CAF (and it's associated tag check + indirect jump) entirely and append a zero-terminate MagicHash string literal via Addr#. Then I discovered that it's 30% faster if you can avoid the strlen with an explicit length. See this benchmark: https://github.com/chadaustin /buffer- builder/blob/ac662962d6d3c21f206ab8e8121323b9f18677fa/bench/Bench.hs#L42 That API is not very pleasant, of course. :) Thus, here is a feature request: It would be great if "foo"## produced (# Int#, Addr# #), where the Int# is the length of the buffer in bytes. The compiler could enforce that the literal only contains 8-bit values. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10064 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10064: Add support for "foo"## literals to MagicHash -------------------------------------+------------------------------------- Reporter: chadaustin | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by hvr): * cc: duncan (added) Comment: I think duncan may have some opinion here... -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10064#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10064: Add support for "foo"## literals to MagicHash -------------------------------------+------------------------------------- Reporter: chadaustin | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by simonpj): Is this the same as #5218? Which needs love. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10064#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10064: Add support for "foo"## literals to MagicHash -------------------------------------+------------------------------------- Reporter: chadaustin | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by chadaustin): Hi! I don't think it's exactly the same as #5218 since I don't specifically need ByteStrings here, just a quick Int#, Addr# pair. But #5218 could definitely be implemented on top of a mechanism that desugars to this (e.g. unpackCStringLen "my literal"##). If you'd like to merge the bugs, that's fine with me, as long as there's a way to get at some machinery to generate string length Int#s at compile time. :) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10064#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10064: Add support for "foo"## literals to MagicHash -------------------------------------+------------------------------------- Reporter: chadaustin | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by simonpj): If they are different, don't merge them. If anyone wants to take this forward, the process is as usual: write a wiki page describing the design in detail; socialise it on ghc-devs and ghc-users, refine. Then implement. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10064#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10064: Add support for "foo"## literals to MagicHash -------------------------------------+------------------------------------- Reporter: chadaustin | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by thomie): * failure: None/Unknown => Runtime performance bug -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10064#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10064: Add support for "foo"## literals to MagicHash -------------------------------------+------------------------------------- Reporter: chadaustin | Owner: (none) Type: feature request | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Resolution: duplicate | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: #5218 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * status: new => closed * resolution: => duplicate * related: => #5218 Comment: I think we should indeed treat this as a duplicate of #5218 as the answer proposed in comment:3 is precisely that which is being implemented in Phab:D2443. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10064#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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