[InstCombine] Iterative replacement in PtrReplacer (#137215)

This patch enhances the PtrReplacer as follows:
1. Users are now collected iteratively to be generous on the stack. In
the case of PHIs with incoming values which have not yet been visited,
they are pushed back into the stack for reconsideration.
2. Replace users of the pointer root in a reverse-postorder traversal,
instead of a simple traversal over the collected users. This reordering
ensures that the operands of an instruction are replaced before
replacing the instruction itself.
3. During the replacement of PHI, use the same incoming value if it does
not have a replacement.

This patch specifically fixes the case when an incoming value of a PHI
is addrspacecasted.

0 files changed, 0 insertions, 0 deletions