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James Molloy a6ee5ed23a [Thumb1] Fix cost calculation for complemented immediates
Materializing something like "-3" can be done as 2 instructions:
  MOV r0, #3
  MVN r0, r0

This has a cost of 2, not 3. It looks like we were already trying to detect this pattern in TII::getIntImmCost(), but were taking the complement of the zero-extended value instead of the sign-extended value which is unlikely to ever produce a number < 256.

There were no tests failing after changing this... :/

llvm-svn: 280928
2016-09-08 12:58:04 +00:00

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469 B
LLVM

; RUN: llc %s -o - -O1 -debug-only=consthoist 2>&1 | FileCheck %s
; REQUIRES: asserts
target datalayout = "e-m:o-p:32:32-f64:32:64-v64:32:64-v128:32:128-a:0:32-n32-S32"
target triple = "thumbv6m-apple-ios8.0.0"
declare void @g(i32)
; CHECK: Collect constant i32 -3 from call void @g(i32 -3) with cost 2
define void @f(i1 %cond) {
entry:
call void @g(i32 -3)
br i1 %cond, label %true, label %ret
true:
call void @g(i32 -3)
br label %ret
ret:
ret void
}