| Sanjay Patel | 41160c2 | 2015-12-30 22:40:52 +0000 | [diff] [blame] | 1 | ; RUN: opt -S -instcombine < %s | FileCheck %s |
| 2 | |
| 3 | ; https://llvm.org/bugs/show_bug.cgi?id=25900 |
| 4 | ; An arithmetic shift right of a power of two is not a power |
| 5 | ; of two if the original value is the sign bit. Therefore, |
| 6 | ; we can't transform the sdiv into a udiv. |
| 7 | |
| 8 | define i32 @pr25900(i32 %d) { |
| 9 | %and = and i32 %d, -2147483648 |
| 10 | ; The next 3 lines prevent another fold from masking the bug. |
| 11 | %ext = zext i32 %and to i64 |
| 12 | %or = or i64 %ext, 4294967296 |
| 13 | %trunc = trunc i64 %or to i32 |
| 14 | %ashr = ashr exact i32 %trunc, 31 |
| 15 | %div = sdiv i32 4, %ashr |
| 16 | ret i32 %div |
| 17 | |
| 18 | ; CHECK: sdiv |
| 19 | } |
| 20 | |