#7116: Missing optimisation: strength reduction of floating-point multiplication
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Reporter: simonmar | Owner: pcapriotti
Type: bug | Status: new
Priority: normal | Milestone: 7.8.1
Component: Compiler | Version: 7.4.2
Resolution: | Keywords:
Operating System: Unknown/Multiple | Architecture:
Type of failure: Runtime performance bug | Unknown/Multiple
Test Case: | Difficulty: Unknown
Blocking: | Blocked By:
| Related Tickets:
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Comment (by jstolarek):
Provded patch rewrites 2 * x for Int and Word to x + x, which kills the
optimisation done at the later stage of the pipeline in !CmmOpt: turning
multiplications and divisons by powers of two into shifts. I wonder if it
makes sense to move mentioned Cmm optimisation to !PrelRules, so that
shifts are introduced at the Core level. Having all similar optimisations
done in one place would be more consistent. Or am I missing something?
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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7116#comment:4>
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