mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-11-17 03:07:06 +00:00
63f97201dc
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
16 lines
362 B
LLVM
16 lines
362 B
LLVM
; RUN: llvm-as < %s | llc -march=x86-64 > %t
|
|
; RUN: not grep add %t
|
|
; RUN: grep subq %t | count 2
|
|
|
|
; The immediate can be encoded in a smaller way if the
|
|
; instruction is a sub instead of an add.
|
|
|
|
define i64 @foo(i64 inreg %a) nounwind {
|
|
%b = add i64 %a, 2147483648
|
|
ret i64 %b
|
|
}
|
|
define i64 @bar(i64 inreg %a) nounwind {
|
|
%b = add i64 %a, 128
|
|
ret i64 %b
|
|
}
|