Re: [Intel-gfx] [PATCH 1/3] treewide: Lift switch variables out of switches

On Wed, Jan 23, 2019 at 04:17:30PM +0200, Jani Nikula wrote:

Can't have:

	switch (i) {
		int j;
	case 0:
        	/* ... */
	}

because it can't be turned into:

	switch (i) {
		int j = 0; /* not valid C */
	case 0:
        	/* ... */
	}

but can have e.g.:

	switch (i) {
	case 0:
		{
			int j = 0;
	        	/* ... */
		}
	}

I think Kees' approach of moving such variable declarations to the
enclosing block scope is better than adding another nesting block.

Another nesting level would be bad, but I think this is OK:

	switch (i) {
	case 0: {
		int j = 0;
        	/* ... */
	}
	case 1: {
		void *p = q;
		/* ... */
	}
	}

I can imagine Kees' patch might have a bad effect on stack consumption,
unless GCC can be relied on to be smart enough to notice the
non-overlapping liveness of the vriables and use the same stack slots
for both.