[llvm-commits] [PATCH] Teach -join-cross-class-copies to intersect register classes

[Jakob Stoklund Olesen]

This patch series teaches -join-register-classes to properly intersect  
register classes when joining two virtual registers. This avoids  
generating bad machine code in the blackfin backend. It should have no  
effect on other targets.

=== 01-tablegen-subclass.patch

Loosen TableGen's definition of a register subclass so a subclass is  
allowed to have a larger spill size. This is consistent with what - 
join-cross-class-copies does now.

See my ramblings here: http://lists.cs.uiuc.edu/pipermail/llvmdev/2009-April/021966.html

This patch is not actually necessary to solve my blackfin problems -  
it ensures that -join-cross-class-copies doesn't change behaviour on  
Alpha, PPC, SPU, and X86 where a register may have multiple spill sizes.

=== 02-intersection-regclass.patch

Implement the intersection(A, B) function that find the largest common  
subclass of two register classes.

=== 03-join-cross-intersection.patch

Use intersection() to determine the new register class of a joined  
virtual register.




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