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1 Commits

Author SHA1 Message Date
Dan Gohman
63f97201dc Fun x86 encoding tricks: when adding an immediate value of 128,
use a SUB instruction instead of an ADD, because -128 can be
encoded in an 8-bit signed immediate field, while +128 can't be.
This avoids the need for a 32-bit immediate field in this case.

A similar optimization applies to 64-bit adds with 0x80000000,
with the 32-bit signed immediate field.

To support this, teach tablegen how to handle 64-bit constants.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@57663 91177308-0d34-0410-b5e6-96231b3b80d8
2008-10-17 01:33:43 +00:00