hanchenye-llvm-project

Commit Graph

Author	SHA1	Message	Date
Dan Gohman	ca0546facc	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	2008-10-17 01:33:43 +00:00
Reid Spencer	83b3d82672	Regression is gone, don't try to find it on clean target. llvm-svn: 33296	2007-01-17 07:59:14 +00:00

Author

SHA1

Message

Date

Dan Gohman

ca0546facc

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

2008-10-17 01:33:43 +00:00

Reid Spencer

83b3d82672

Regression is gone, don't try to find it on clean target.

llvm-svn: 33296

2007-01-17 07:59:14 +00:00

2 Commits