Re: [PATCH] c: Fix ICE with cast to VLA [93576]

[Jeff Law <law@redhat.com>]

On Thu, 2020-02-13 at 18:57 +0100, Jakub Jelinek wrote:
> Hi!
> 
> The following testcase ICEs, because the PR84305 changes try to evaluate
> the size earlier.  If size has side-effects, that is desirable, and the
> side-effects will actually be wrapped in a SAVE_EXPR.  The problem on this
> testcase is that there are no side-effects, and c_fully_fold doesn't fold
> those COMPOUND_EXPRs to constant, and while before gimplification we unshare
> trees found in the expressions, the unsharing doesn't involve TYPE_SIZE etc.
> of used types.  Gimplification is destructive though, so when we gimplify
> the two nested COMPOUND_EXPRs and then try to gimplify it the second time
> for the TYPE_SIZEs, we ICE.
> Now, we could use unshare_expr in what we push to *expr, SAVE_EXPRs and
> their operands in there aren't unshared, but I really don't see a point of
> evaluating expressions that don't have side-effects before, so instead
> this just pushes there expressions that do have side-effects.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk and
> release branches?
> 
> 2020-02-13  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR c/93576
> 	* c-decl.c (grokdeclarator): If this_size_varies, only push size into
> 	*expr if it has side effects.
> 
> 	* gcc.dg/pr93576.c: New test.
OK
jeff
>