slsr: Fix some undefined/overflow introducing bugs in SLSR [PR106883]

slsr: Fix some undefined/overflow introducing bugs in SLSR [PR106883]

This fixes the first part of SLSR incorrectly inserting undefined code (overflow)
into the IR. The easiest way is to rewrite the statement after creating it
using rewrite_to_defined_unconditional.
This fixes the testcases from PR 121347 (and a few others) which all cause an
infinite loops to appear.
I will be posting the fix for replace_rhs_if_not_dup later and at that point I
will add a few testcases.

Bootstrapped and tested on x86_64-linux-gnu with no regressions.

	PR tree-optimization/121347
	PR tree-optimization/106883
gcc/ChangeLog:

	* gimple-ssa-strength-reduction.cc (insert_initializers): Rewrite
	newly inserted statements for undefinedness (overflow).

Signed-off-by: Andrew Pinski <andrew.pinski@oss.qualcomm.com>