File: 2012-03-26-FoldImmBug.ll

package info (click to toggle)
llvm-toolchain-14 1%3A14.0.6-12
  • links: PTS, VCS
  • area: main
  • in suites: bookworm
  • size: 1,496,180 kB
  • sloc: cpp: 5,593,972; ansic: 986,872; asm: 585,869; python: 184,223; objc: 72,530; lisp: 31,119; f90: 27,793; javascript: 9,780; pascal: 9,762; sh: 9,482; perl: 7,468; ml: 5,432; awk: 3,523; makefile: 2,538; xml: 953; cs: 573; fortran: 567
file content (33 lines) | stat: -rw-r--r-- 1,098 bytes parent folder | download | duplicates (36) 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
 
; RUN: llc < %s -mtriple=thumbv7-apple-ios -mcpu=cortex-a8 | FileCheck %s

; ARM has a peephole optimization which looks for a def / use pair. The def
; produces a 32-bit immediate which is consumed by the use. It tries to 
; fold the immediate by breaking it into two parts and fold them into the
; immmediate fields of two uses. e.g
;        movw    r2, #40885
;        movt    r3, #46540
;        add     r0, r0, r3
; =>
;        add.w   r0, r0, #3019898880
;        add.w   r0, r0, #30146560
;
; However, this transformation is incorrect if the user produces a flag. e.g.
;        movw    r2, #40885
;        movt    r3, #46540
;        adds    r0, r0, r3
; =>
;        add.w   r0, r0, #3019898880
;        adds.w  r0, r0, #30146560
; Note the adds.w may not set the carry flag even if the original sequence
; would.
;
; rdar://11116189
define i64 @t(i64 %aInput) nounwind {
; CHECK-LABEL: t:
; CHECK: movs [[REG:(r[0-9]+)]], #0
; CHECK: movt [[REG]], #46540
; CHECK: adds r{{[0-9]+}}, r{{[0-9]+}}, [[REG]]
  %1 = mul i64 %aInput, 1000000
  %2 = add i64 %1, -7952618389194932224
  ret i64 %2
}