MSP430: Dont add offsets to addresses when emitting asm for post_inc

MSP430: Dont add offsets to addresses when emitting asm for post_inc

Some insns, which operate on SImode operands, output assembler template
that comprise of multiple instructions using HImode operands. To access
the high word of an SImode operand, an operand selector '%H' is used to
offset the operand value by a constant amount.

When one of these HImode operands is a memory reference to a post_inc,
the address does not need to be offset, since the preceding instruction
has already offset the address to the correct value.

This fixes an ICE in change_address_1, at emit-rtl.c:2318 for
gcc.c-torture/execute/pr20527-1.c in the "-mlarge -O2 -flto
-fuse-linker-plugin -fno-fat-lto-objects" configuration.

This test generated the following insn, and the attempt to output the
high part of the post_inc address caused the ICE.
(set (reg:SI 6 R6)
     (minus:SI (reg:SI 6 R6)
               (mem:SI (post_inc:PSI (reg:PSI 10 R10)) {subsi3}

gcc/ChangeLog:

2020-04-13  Jozef Lawrynowicz  <jozef.l@mittosystems.com>

	* config/msp430/msp430.c (msp430_print_operand): Don't add offsets to
	memory references in %B, %C and %D operand selectors when the inner
	operand is a post increment address.