[GHC] #14233: Remove old GetTickCount() code path for Windows

[GHC]

#14233: Remove old GetTickCount() code path for Windows
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           Reporter:  nh2               |             Owner:  (none)
               Type:  task              |            Status:  new
           Priority:  normal            |         Milestone:
          Component:  Compiler          |           Version:  8.3
           Keywords:                    |  Operating System:  Windows
       Architecture:  Unknown/Multiple  |   Type of failure:  None/Unknown
          Test Case:                    |        Blocked By:
           Blocking:                    |   Related Tickets:
Differential Rev(s):                    |         Wiki Page:
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 Windows XP support was dropped since GHC 8.0 as per
 https://ghc.haskell.org/trac/ghc/wiki/WindowsGhc

 In `HsWord64 getMonotonicNSec()` on Windows we still fall back to the
 32-bit `GetTickCount()` if `QueryPerformanceFrequency()` is not supported:
 [https://github.com/ghc/ghc/blob/ghc-8.2.1-release/rts/win32/GetTime.c#L69
 Code]

 But [https://msdn.microsoft.com/en-
 us/library/windows/desktop/ms644905(v=vs.85).aspx Microsoft's
 documentation] says that `QueryPerformanceFrequency()` is guaranteed to be
 supported on Windows >= XP:

 > On systems that run Windows XP or later, the function will always
 succeed and will thus never return zero.

 Thus we can remove the `if (!qpc_supported)` check and all `if
 (!qpc_frequency.QuadPart)` code paths, and replace it with an assertion or
 a `./configure` check.

 We can also add a comment that `getMonotonicNSec()` will indeed always
 make use of the whole 64-bit domain.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14233>
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