[CVP] Failure to recognise trunc nsw from assumptions

[RKSimon]

Pulled out of #130088

----------------------------------------
define i8 @src(i16 noundef %x) {
#0:
  %add = add i16 noundef %x, 128
  %or.cond.i = icmp ult i16 %add, 256
  assume i1 %or.cond.i
  %conv1 = trunc i16 noundef %x to i8
  ret i8 %conv1
}
=>
define i8 @tgt(i16 noundef %x) {
#0:
  %conv1 = trunc nsw i16 noundef %x to i8
  ret i8 %conv1
}
Transformation seems to be correct!

https://alive2.llvm.org/ce/z/2qhZy4

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

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If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Simon Pilgrim (RKSimon)

Pulled out of #130088 ```ll ---------------------------------------- define i8 @src(i16 noundef %x) { #0: %add = add i16 noundef %x, 128 %or.cond.i = icmp ult i16 %add, 256 assume i1 %or.cond.i %conv1 = trunc i16 noundef %x to i8 ret i8 %conv1 } => define i8 @tgt(i16 noundef %x) { #0: %conv1 = trunc nsw i16 noundef %x to i8 ret i8 %conv1 } Transformation seems to be correct! ``` https://alive2.llvm.org/ce/z/2qhZy4

[bababuck]

@dtcxzyw Can iI give this a go if no one else is already working on it?

[ArunaHulakoti]

@llvmbot Could you please provide more details on the expected behavior?

[dtcxzyw]

@dtcxzyw Can iI give this a go if no one else is already working on it?

Sorry to tell you that this issue is covered by #130504.