[Patch 1/2] Don't put out a call to memcpy for volatile struct operations

[James Greenhalgh]

Hi,

Andrew is quite right, we break the contract for volatile struct copies
if we start double copying bytes.

But, the generic code will call memcpy - at which point anything could
happen. So, we must not put out a call to memcpy if either our source or
destination operands are volatile. The same is true of memset, so also
disable that call for volatile operands, and add a fallback loop
implementation.

Bootstrapped on x86, Arm and AArch64 with no issues.

OK?

Thanks,
James

---
gcc/

2014-08-21  James Greenhalgh  <james.greenhalgh@arm.com>

	* expr.c (set_storage_via_loop): New.
	(emit_block_move_hints): Do not call memcpy with volatile operands.
	(emit_block_move_via_movmem): Clarify that targets do have to care
	about volatile operands.
	(clear_storage_hints): Do not call memset for volatile operands,
	fall back to a loop implementation.

gcc/testsuite/

2014-08-21  James Greenhalgh  <james.greenhalgh@arm.com>

	* gcc.dg/large-volatile-struct-copy-1.c: New.
	* gcc.dg/large-volatile-struct-set-1.c: Likewise.
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