[GHC] #11578: Fix GHC on AArch64/Arm64

[GHC]

#11578: Fix GHC on AArch64/Arm64
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        Reporter:  erikd             |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:  aarch64
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by mfox):

 Something I've heard about but don't fully understand the implications (if
 any) for ghc:

 * Some programs assume that a page size is 4k. Arm64 can have larger and
 smaller pages.
 * Some programs assume 47-bit virtual address space with bit 48 signaling
 kernel space; the feel free to use bits [63:49] of a pointer as a tag.
 Arm64 Doesn't like it. Can still use bits [63:56] as a tag

 Again, I don't know the implications for ghc. Just mentioning it in case
 someone knows more.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11578#comment:4>
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