#2269: Word type to Double or Float conversions are slower than Int conversions -------------------------------------+------------------------------------- Reporter: dons | Owner: dons@… Type: feature request | Status: new Priority: lowest | Milestone: Component: Compiler | Version: 6.8.2 Resolution: | Keywords: rules, | performance, double, newcomer Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by rwbarton): * keywords: rules, performance, double => rules, performance, double, newcomer Comment: Namely, {{{ double f(unsigned long x) { return x; } /* 0000000000000000 <f>: 0: 66 48 0f 6e cf movq %rdi,%xmm1 5: 66 0f 62 0d 00 00 00 punpckldq 0x0(%rip),%xmm1 # d <f+0xd> c: 00 9: R_X86_64_PC32 .LCPI0_0-0x4 d: 66 0f 5c 0d 00 00 00 subpd 0x0(%rip),%xmm1 # 15 <f+0x15> 14: 00 11: R_X86_64_PC32 .LCPI0_1-0x4 15: 66 0f 70 c1 4e pshufd $0x4e,%xmm1,%xmm0 1a: 66 0f 58 c1 addpd %xmm1,%xmm0 1e: c3 retq */ }}} Compiling the test program here with LLVM there's no measurable difference between the int and word versions, so I guess doing this is worthwhile. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2269#comment:22> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler