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| author | Dan Gohman <gohman@apple.com> | 2008-10-17 01:33:43 +0000 |
|---|---|---|
| committer | Dan Gohman <gohman@apple.com> | 2008-10-17 01:33:43 +0000 |
| commit | ca0546facc5af4c27a5efd5ff80935ba05ae030a (patch) | |
| tree | e41965726caebfa000f4fefdfc491d4ad93cb745 /llvm/lib/Transforms | |
| parent | a39b0a1f05337718973fb9a52df61b302e766109 (diff) | |
| download | bcm5719-llvm-ca0546facc5af4c27a5efd5ff80935ba05ae030a.tar.gz bcm5719-llvm-ca0546facc5af4c27a5efd5ff80935ba05ae030a.zip | |
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.
llvm-svn: 57663
Diffstat (limited to 'llvm/lib/Transforms')
0 files changed, 0 insertions, 0 deletions
