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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 | 63f97201dc9dcebbe84d1b73113166c64212b4b8 (patch) | |
| tree | 718d542a3b0cf7a6c76944afed13d26afbb6a12f /lib/Target/CBackend/CBackend.cpp | |
| parent | 74feef261a43392bc85280f66c75fbd4e2ccf73d (diff) | |
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
Diffstat (limited to 'lib/Target/CBackend/CBackend.cpp')
0 files changed, 0 insertions, 0 deletions