Add handling of MULT_EXPR/PLUS_EXPR for wrapping overflow in affine combination(PR83403)

Add handling of MULT_EXPR/PLUS_EXPR for wrapping overflow in affine combination(PR83403)

Use determine_value_range to get value range info for fold convert expressions
with internal operation PLUS_EXPR/MINUS_EXPR/MULT_EXPR when not overflow on
wrapping overflow inner type.  i.e.:

(long unsigned int)((unsigned int)n * 10 + 1)
=>
(long unsigned int)n * (long unsigned int)10 + (long unsigned int)1

With this patch for affine combination, load/store motion could detect
more address refs independency and promote some memory expressions to
registers within loop.

PS: Replace the previous "(T1)(X + CST) as (T1)X - (T1)(-CST))"
to "(T1)(X + CST) as (T1)X + (T1)(CST))" for wrapping overflow.

Bootstrap and regression tested pass on Power8-LE.

gcc/ChangeLog

	2020-05-11  Xiong Hu Luo  <luoxhu@linux.ibm.com>

	PR tree-optimization/83403
	* tree-affine.c (expr_to_aff_combination): Replace SSA_NAME with
	determine_value_range, Add fold conversion of MULT_EXPR, fix the
	previous PLUS_EXPR.

gcc/testsuite/ChangeLog

	2020-05-11  Xiong Hu Luo  <luoxhu@linux.ibm.com>

	PR tree-optimization/83403
	* gcc.dg/tree-ssa/pr83403-1.c: New test.
	* gcc.dg/tree-ssa/pr83403-2.c: New test.
	* gcc.dg/tree-ssa/pr83403.h: New header.