#1512: NCG to handle cyclic fixups for rematching register assignment for jump
blocks
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Reporter: guest | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version:
Severity: normal | Resolution:
Keywords: | Difficulty: Moderate (1 day)
Os: Unknown | Testcase:
Architecture: Unknown |
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Comment (by duncan):
{{{
Basically, we have to move A to B, and B to A. There is no move sequence
that allows this without using a scratch register.
}}}
As Ian pointed out, actually there is!
{{{
x := x `xor` y;
y := x `xor` y;
x := x `xor` y
}}}
This might give you a cheaper way out than spilling and using a scratch
register.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1512>
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