[InstCombine] Fold max/min when incrementing/decrementing by 1 (#142466)

Add the following folds for integer min max folding in InstCombine:
 -  (X > Y) ? X : (Y - 1) ==> MIN(X, Y - 1)
 -  (X < Y) ? X : (Y + 1) ==> MAX(X, Y + 1)

These are safe when overflow corresponding to the sign of the comparison
is poison. (proof https://alive2.llvm.org/ce/z/oj5iiI).

The most common of these patterns is likely the minimum case which
occurs in some internal library code when clamping an integer index to a
range (The maximum cases are included for completeness). Here is a
simplified example:

int clampToWidth(int idx, int width) {
  if (idx >= width)
    return width - 1;
  return idx;
}

https://cuda.godbolt.org/z/nhPzWrc3W

0 files changed, 0 insertions, 0 deletions