Re: [PATCH v2] Fix PR64242

[Jeff Law <law@redhat.com>]

On 5/28/19 11:26 AM, Wilco Dijkstra wrote:
> Improve the fix for PR64242.  Various optimizations can change a memory reference
> into a frame access.  Given there are multiple virtual frame pointers which may
> be replaced by multiple hard frame pointers, there are no checks for writes to the
> various frame pointers.  So updates to a frame pointer tends to generate incorrect
> code.  Improve the previous fix to also add clobbers of several frame pointers and
> add a scheduling barrier.  This should work in most cases until GCC supports a
> generic "don't optimize across this instruction" feature.
> 
> Bootstrap OK. Testcase passes on AArch64 and x86-64.  Inspected x86, Arm,
> Thumb-1 and Thumb-2 assembler which looks correct. 
> 
> ChangeLog:
> 2018-12-07  Wilco Dijkstra  <wdijkstr@arm.com>
> 
> gcc/
> 	PR middle-end/64242
> 	* builtins.c (expand_builtin_longjmp): Add frame clobbers and schedule block.
> 	(expand_builtin_nonlocal_goto): Likewise.
> 
> testsuite/
> 	PR middle-end/64242
> 	* gcc.c-torture/execute/pr64242.c: Update test.
OK.  Though given history we might expect some targets to barf on the
test changes.  Please keep an eye out for such breakage.

jeff