File: known-power-of-two.ll

package info (click to toggle)
llvm-toolchain-11 1%3A11.0.1-2
  • links: PTS, VCS
  • area: main
  • in suites: bullseye
  • size: 995,808 kB
  • sloc: cpp: 4,767,656; ansic: 760,916; asm: 477,436; python: 170,940; objc: 69,804; lisp: 29,914; sh: 23,855; f90: 18,173; pascal: 7,551; perl: 7,471; ml: 5,603; awk: 3,489; makefile: 2,573; xml: 915; cs: 573; fortran: 503; javascript: 452
file content (20 lines) | stat: -rw-r--r-- 573 bytes parent folder | download | duplicates (20) 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
 
; RUN: opt -S -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
}