llvm-project/llvm/test/CodeGen/X86/add-trick32.ll

; RUN: llc < %s -march=x86 > %t
; RUN: not grep add %t
; RUN: grep subl %t | count 1

; The immediate can be encoded in a smaller way if the
; instruction is a sub instead of an add.

define i32 @foo(i32 inreg %a) nounwind {
  %b = add i32 %a, 128
  ret i32 %b
}
Eliminate more uses of llvm-as and llvm-dis. llvm-svn: 81290 2009-09-09 07:54:48 +08:00			`; RUN: llc < %s -march=x86 > %t`
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 09:33:43 +08:00			`; RUN: not grep add %t`
			`; RUN: grep subl %t \| count 1`

			`; The immediate can be encoded in a smaller way if the`
			`; instruction is a sub instead of an add.`

			`define i32 @foo(i32 inreg %a) nounwind {`
			`%b = add i32 %a, 128`
			`ret i32 %b`
			`}`