[llvm] [ValueTracking] Refactor `isKnownNonEqualFromContext` (PR #127388)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

Case 1 (regression):
```
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"

define void @Dau_DecFindSets_int(i32 %0, i1 %1) {
  br label %3

3:                                                ; preds = %Dau_DecCheckSetTop.exit, %2
  %.081 = phi i32 [ 0, %2 ], [ %0, %Dau_DecCheckSetTop.exit ]
  br label %Dau_DecCheckSetTop.exit

Dau_DecCheckSetTop.exit:                          ; preds = %._crit_edge.i.i, %4, %3
  br i1 %1, label %4, label %3

4:                                                ; preds = %Dau_DecCheckSetTop.exit
  %5 = and i32 %0, 1
  %6 = icmp eq i32 %5, %.081
  br i1 %6, label %7, label %Dau_DecCheckSetTop.exit

7:                                                ; preds = %4
  br label %._crit_edge.i.i

._crit_edge.i.i:                                  ; preds = %7
  %.not.i.i = icmp eq i32 %.081, 31
  br i1 %.not.i.i, label %.preheader.i.i, label %Dau_DecCheckSetTop.exit

.preheader.i.i:                                   ; preds = %._crit_edge.i.i
  ret void
}
```
With this patch, we do not add `%.081` for the condition `%6 = icmp eq i32 %5, %.081`. Thus `%.not.i.i = icmp eq i32 %.081, 31` cannot be folded into false.



https://github.com/llvm/llvm-project/pull/127388