File: known-power-of-two.ll

package info (click to toggle)
llvm-toolchain-17 1%3A17.0.6-22
  • links: PTS, VCS
  • area: main
  • in suites: forky, sid, trixie
  • size: 1,799,624 kB
  • sloc: cpp: 6,428,607; ansic: 1,383,196; asm: 793,408; python: 223,504; objc: 75,364; f90: 60,502; lisp: 33,869; pascal: 15,282; sh: 9,684; perl: 7,453; ml: 4,937; awk: 3,523; makefile: 2,889; javascript: 2,149; xml: 888; fortran: 619; cs: 573
file content (20 lines) | stat: -rw-r--r-- 580 bytes parent folder | download | duplicates (4) 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
 
; RUN: opt -S -passes=instcombine < %s | FileCheck %s

; https://llvm.org/bugs/show_bug.cgi?id=25900
; An arithmetic shift right of a power of two is not a power
; of two if the original value is the sign bit. Therefore,
; we can't transform the sdiv into a udiv.

define i32 @pr25900(i32 %d) {
  %and = and i32 %d, -2147483648
; The next 3 lines prevent another fold from masking the bug.
  %ext = zext i32 %and to i64
  %or = or i64 %ext, 4294967296
  %trunc = trunc i64 %or to i32
  %ashr = ashr exact i32 %trunc, 31
  %div = sdiv i32 4, %ashr
  ret i32 %div

; CHECK: sdiv
}