Am Donnerstag, den 23.09.2021, 17:37 -0400 schrieb Jason Merrill:
> On 9/23/21 15:49, Uecker, Martin wrote:
> > Am Mittwoch, den 22.09.2021, 17:18 -0400 schrieb Jason Merrill:
> > > On 9/5/21 15:14, Uecker, Martin wrote:
> > > > Here is the third version of the patch. This also
> > > > fixes the index zero case. Thus, this should be
> > > > a complete fix for 91038 and should fix all cases
> > > > also supported by clang. Still not working is
> > > > returning a struct of variable size from a
> > > > statement expression (29970) when the size depends
> > > > on computations inside the statement expression.
> > > >
> > > > Bootstrapped and regression tested
> > > > on x86-64 for all languages.
> > > >
> > > > Martin
> > > >
> > > >
> > > >
> > > >
> > > > Fix ICE when mixing VLAs and statement expressions [PR91038]
> > > >
> > > > When returning VM-types from statement expressions, this can
> > > > lead to an ICE when declarations from the statement expression
> > > > are referred to later. Most of these issues can be addressed by
> > > > gimplifying the base expression earlier in gimplify_compound_lval.
> > > > Another issue is fixed by not reording some size-related expressions
> > > > during folding. This fixes PR91038 and some of the test cases
> > > > from PR29970 (structs with VLA members need further work).
> > > >
> > > >
> > > > 2021-08-01 Martin Uecker <[email protected]>
> > > >
> > > > gcc/
> > > > PR c/91038
> > > > PR c/29970
> > > > * gimplify.c (gimplify_var_or_parm_decl): Update comment.
> > > > (gimplify_compound_lval): Gimplify base expression first.
> > > > (gimplify_target_expr): Do not gimplify size expression.
> > > > * fold-const.c (fold_binary_loc): Do not reorder SAVE_EXPR
> > > > in pointer arithmetic for variably modified types.
> > > >
> > > > gcc/testsuite/
> > > > PR c/91038
> > > > PR c/29970
> > > > * gcc.dg/vla-stexp-3.c: New test.
> > > > * gcc.dg/vla-stexp-4.c: New test.
> > > > * gcc.dg/vla-stexp-5.c: New test.
> > > > * gcc.dg/vla-stexp-6.c: New test.
> > > > * gcc.dg/vla-stexp-7.c: New test.
> > > > * gcc.dg/vla-stexp-8.c: New test.
> > > > * gcc.dg/vla-stexp-9.c: New test.
> > > >
> > > >
> > > > diff --git a/gcc/fold-const.c b/gcc/fold-const.c
> > > > index ff23f12f33c..1e6f50692b5 100644
> > > > --- a/gcc/fold-const.c
> > > > +++ b/gcc/fold-const.c
> > > > @@ -10854,7 +10854,15 @@ fold_binary_loc (location_t loc, enum
> > > > tree_code code, tree type,
> > > > return build2_loc (loc, COMPOUND_EXPR, type, TREE_OPERAND
> > > > (arg0, 0),
> > > > tem);
> > > > }
> > > > - if (TREE_CODE (arg1) == COMPOUND_EXPR)
> > > > + /* This interleaves execution of the two sub-expressions
> > > > + which is allowed in C. For pointer arithmetic when the
> > > > + the pointer has a variably modified type, the right expression
> > > > + might have a SAVE_EXPR which depends on the left expr, so
> > > > + do not fold in this case. */
> > > > + if (TREE_CODE (arg1) == COMPOUND_EXPR
> > > > + && !(code == POINTER_PLUS_EXPR
> > > > + && TREE_CODE (TREE_OPERAND (arg1, 0)) == SAVE_EXPR)
> > > > + && variably_modified_type_p (type, NULL_TREE))
> > >
> > > This seems pretty fragile. If the problem is that the SAVE_EXPR depends
> > > on a statement-expr on the LHS, can't that happen with expressions other
> > > than POINTER_PLUS_EXPR?
> >
> > I intentionally limited the change to this specific
> > case to avoid accidentally breaking or pessimizing
> > anything else. I did not notice any other cases that
> > need fixing. It is of course possible that
> > I have missed some...
> >
> > > Maybe we should include the statement-expr in the SAVE_EXPR?
> >
> > I am not really sure how to implement this.
>
> Nor am I, I'm not at all familiar with the VLA handling code. But if
> the generated trees rely on evaluation happening with a stricter order
> than is actually guaranteed, that seems like a bug in the generation of
> the expression trees, not the folding code.
Is there a definition about what is guaranteed?
It seems to be based on the somewhat scary
C semantics where in
(a, b) op (c, d)
evaluation order could be
a, c, b, d.
If I remember correctly
({ int N; int x[N]; &x; })[0]
becomes
TARGET_EXPR <D, { int N; int x[N]; D = &x }> + (SAVE_EXPR <N> * 0)
which (somehow involving the rule above) becomes
SAVE_EXPR <N>; TARGET_EXPR <D, { int N; int x[N]; D = &x })
which then fails to gimplify.
It is not entirely clear to me what code the FE
should generate to avoid this.
> Could someone that knows more about VLA weigh in?
> > Maybe we could apply this patch first (because
> > I have to work around this bug in a couple of
> > projects which is a bit annoying)? I am happy
> > to implement an alternative later if there is
> > a better way (which I can understand).
>
> The gimplify_compound_lval change is OK now.
>
> What's the rationale for the gimplify_target_expr change?
It seems another case where size expressions are
gimplified earlier than expressions they might
depend
on.
But I can't seem to find a case anymore where this
change makes a difference.
Martin
> > > > {
> > > > tem = fold_build2_loc (loc, code, type, op0,
> > > > fold_convert_loc (loc, TREE_TYPE (op1),
> > > > diff --git a/gcc/gimplify.c b/gcc/gimplify.c
> > > > index 99d1c7fcce4..8ee205f593c 100644
> > > > --- a/gcc/gimplify.c
> > > > +++ b/gcc/gimplify.c
> > > > @@ -2840,7 +2840,10 @@ gimplify_var_or_parm_decl (tree *expr_p)
> > > > declaration, for which we've already issued an error. It would
> > > > be really nice if the front end wouldn't leak these at all.
> > > > Currently the only known culprit is C++ destructors, as seen
> > > > - in g++.old-deja/g++.jason/binding.C. */
> > > > + in g++.old-deja/g++.jason/binding.C.
> > > > + Another possible culpit are size expressions for variably modified
> > > > + types which are lost in the FE or not gimplified correctly.
> > > > + */
> > > > if (VAR_P (decl)
> > > > && !DECL_SEEN_IN_BIND_EXPR_P (decl)
> > > > && !TREE_STATIC (decl) && !DECL_EXTERNAL (decl)
> > > > @@ -2985,16 +2988,22 @@ gimplify_compound_lval (tree *expr_p,
> > > > gimple_seq *pre_p, gimple_seq
> > > > *post_p,
> > > > expression until we deal with any variable bounds, sizes, or
> > > > positions in order to deal with PLACEHOLDER_EXPRs.
> > > >
> > > > - So we do this in three steps. First we deal with the annotations
> > > > - for any variables in the components, then we gimplify the base,
> > > > - then we gimplify any indices, from left to right. */
> > > > + The base expression may contain a statement expression that
> > > > + has declarations used in size expressions, so has to be
> > > > + gimplified before gimplifying the size expressions.
> > > > +
> > > > + So we do this in three steps. First we deal with variable
> > > > + bounds, sizes, and positions, then we gimplify the base,
> > > > + then we deal with the annotations for any variables in the
> > > > + components and any indices, from left to right. */
> > > > +
> > > > for (i = expr_stack.length () - 1; i >= 0; i--)
> > > > {
> > > > tree t = expr_stack[i];
> > > >
> > > > if (TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) ==
> > > > ARRAY_RANGE_REF)
> > > > {
> > > > - /* Gimplify the low bound and element type size and put them
> > > > into
> > > > + /* Deal with the low bound and element type size and put them
> > > > into
> > > > the ARRAY_REF. If these values are set, they have already
> > > > been
> > > > gimplified. */
> > > > if (TREE_OPERAND (t, 2) == NULL_TREE)
> > > > @@ -3003,18 +3012,8 @@ gimplify_compound_lval (tree *expr_p, gimple_seq
> > > > *pre_p, gimple_seq
> > > > *post_p,
> > > > if (!is_gimple_min_invariant (low))
> > > > {
> > > > TREE_OPERAND (t, 2) = low;
> > > > - tret = gimplify_expr (&TREE_OPERAND (t, 2), pre_p,
> > > > - post_p, is_gimple_reg,
> > > > - fb_rvalue);
> > > > - ret = MIN (ret, tret);
> > > > }
> > > > }
> > > > - else
> > > > - {
> > > > - tret = gimplify_expr (&TREE_OPERAND (t, 2), pre_p, post_p,
> > > > - is_gimple_reg, fb_rvalue);
> > > > - ret = MIN (ret, tret);
> > > > - }
> > > >
> > > > if (TREE_OPERAND (t, 3) == NULL_TREE)
> > > > {
> > > > @@ -3031,18 +3030,8 @@ gimplify_compound_lval (tree *expr_p, gimple_seq
> > > > *pre_p, gimple_seq
> > > > *post_p,
> > > > elmt_size, factor);
> > > >
> > > > TREE_OPERAND (t, 3) = elmt_size;
> > > > - tret = gimplify_expr (&TREE_OPERAND (t, 3), pre_p,
> > > > - post_p, is_gimple_reg,
> > > > - fb_rvalue);
> > > > - ret = MIN (ret, tret);
> > > > }
> > > > }
> > > > - else
> > > > - {
> > > > - tret = gimplify_expr (&TREE_OPERAND (t, 3), pre_p, post_p,
> > > > - is_gimple_reg, fb_rvalue);
> > > > - ret = MIN (ret, tret);
> > > > - }
> > > > }
> > > > else if (TREE_CODE (t) == COMPONENT_REF)
> > > > {
> > > > @@ -3062,18 +3051,8 @@ gimplify_compound_lval (tree *expr_p, gimple_seq
> > > > *pre_p, gimple_seq
> > > > *post_p,
> > > > offset, factor);
> > > >
> > > > TREE_OPERAND (t, 2) = offset;
> > > > - tret = gimplify_expr (&TREE_OPERAND (t, 2), pre_p,
> > > > - post_p, is_gimple_reg,
> > > > - fb_rvalue);
> > > > - ret = MIN (ret, tret);
> > > > }
> > > > }
> > > > - else
> > > > - {
> > > > - tret = gimplify_expr (&TREE_OPERAND (t, 2), pre_p, post_p,
> > > > - is_gimple_reg, fb_rvalue);
> > > > - ret = MIN (ret, tret);
> > > > - }
> > > > }
> > > > }
> > > >
> > > > @@ -3084,21 +3063,34 @@ gimplify_compound_lval (tree *expr_p,
> > > > gimple_seq *pre_p, gimple_seq
> > > > *post_p,
> > > > fallback | fb_lvalue);
> > > > ret = MIN (ret, tret);
> > > >
> > > > - /* And finally, the indices and operands of ARRAY_REF. During this
> > > > - loop we also remove any useless conversions. */
> > > > + /* Step 3: gimplify size expressions and the indices and operands of
> > > > + ARRAY_REF. During this loop we also remove any useless
> > > > conversions. */
> > > > +
> > > > for (; expr_stack.length () > 0; )
> > > > {
> > > > tree t = expr_stack.pop ();
> > > >
> > > > if (TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) ==
> > > > ARRAY_RANGE_REF)
> > > > {
> > > > + /* Gimplify the low bound and element type size. */
> > > > + tret = gimplify_expr (&TREE_OPERAND (t, 2), pre_p, post_p,
> > > > + is_gimple_reg, fb_rvalue);
> > > > + ret = MIN (ret, tret);
> > > > +
> > > > + tret = gimplify_expr (&TREE_OPERAND (t, 3), pre_p, post_p,
> > > > + is_gimple_reg, fb_rvalue);
> > > > + ret = MIN (ret, tret);
> > > > +
> > > > /* Gimplify the dimension. */
> > > > - if (!is_gimple_min_invariant (TREE_OPERAND (t, 1)))
> > > > - {
> > > > - tret = gimplify_expr (&TREE_OPERAND (t, 1), pre_p, post_p,
> > > > - is_gimple_val, fb_rvalue);
> > > > - ret = MIN (ret, tret);
> > > > - }
> > > > + tret = gimplify_expr (&TREE_OPERAND (t, 1), pre_p, post_p,
> > > > + is_gimple_val, fb_rvalue);
> > > > + ret = MIN (ret, tret);
> > > > + }
> > > > + else if (TREE_CODE (t) == COMPONENT_REF)
> > > > + {
> > > > + tret = gimplify_expr (&TREE_OPERAND (t, 2), pre_p, post_p,
> > > > + is_gimple_reg, fb_rvalue);
> > > > + ret = MIN (ret, tret);
> > > > }
> > > >
> > > > STRIP_USELESS_TYPE_CONVERSION (TREE_OPERAND (t, 0));
> > > > @@ -6766,8 +6758,8 @@ gimplify_target_expr (tree *expr_p, gimple_seq
> > > > *pre_p, gimple_seq
> > > > *post_p)
> > > > to the temps list. Handle also variable length TARGET_EXPRs.
> > > > */
> > > > if (!poly_int_tree_p (DECL_SIZE (temp)))
> > > > {
> > > > - if (!TYPE_SIZES_GIMPLIFIED (TREE_TYPE (temp)))
> > > > - gimplify_type_sizes (TREE_TYPE (temp), pre_p);
> > > > + /* FIXME: this is correct only when the size of the type does
> > > > + not depend on expressions evaluated in init. */
> > > > gimplify_vla_decl (temp, pre_p);
> > > > }
> > > > else
> > > > diff --git a/gcc/testsuite/gcc.dg/vla-stexp-3.c
> > > > b/gcc/testsuite/gcc.dg/vla-stexp-3.c
> > > > new file mode 100644
> > > > index 00000000000..e663de1cd72
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/gcc.dg/vla-stexp-3.c
> > > > @@ -0,0 +1,11 @@
> > > > +/* PR91038 */
> > > > +/* { dg-do compile } */
> > > > +/* { dg-options "" } */
> > > > +
> > > > +
> > > > +void bar(void)
> > > > +{
> > > > + ({ int N = 2; int (*x)[9][N] = 0; x; })[1];
> > > > + ({ int N = 2; int (*x)[9][N] = 0; x; })[0]; // should not
> > > > ice
> > > > +}
> > > > +
> > > > diff --git a/gcc/testsuite/gcc.dg/vla-stexp-4.c
> > > > b/gcc/testsuite/gcc.dg/vla-stexp-4.c
> > > > new file mode 100644
> > > > index 00000000000..612b5a802fc
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/gcc.dg/vla-stexp-4.c
> > > > @@ -0,0 +1,94 @@
> > > > +/* PR29970, PR91038 */
> > > > +/* { dg-do run } */
> > > > +/* { dg-options "-O0 -Wunused-variable" } */
> > > > +
> > > > +int foo3b(void) // should not return 0
> > > > +{
> > > > + int n = 0;
> > > > + return sizeof *({ n = 10; int x[n]; &x; });
> > > > +}
> > > > +
> > > > +int foo4(void) // should not ICE
> > > > +{
> > > > + return (*({
> > > > + int n = 20;
> > > > + char (*x)[n][n] = __builtin_malloc(n * n);
> > > > + (*x)[12][1] = 1;
> > > > + x;
> > > > + }))[12][1];
> > > > +}
> > > > +
> > > > +int foo5(void) // should return 1, returns 0
> > > > +{
> > > > + int n = 0;
> > > > + return (*({
> > > > + n = 20;
> > > > + char (*x)[n][n] = __builtin_malloc(n * n);
> > > > + (*x)[12][1] = 1;
> > > > + (*x)[0][1] = 0;
> > > > + x;
> > > > + }))[12][1];
> > > > +}
> > > > +
> > > > +int foo5c(void) // should return 400
> > > > +{
> > > > + int n = 0;
> > > > + return sizeof(*({
> > > > + n = 20;
> > > > + char (*x)[n][n] = __builtin_malloc(n * n);
> > > > + (*x)[12][1] = 1;
> > > > + (*x)[0][1] = 0;
> > > > + x;
> > > > + }));
> > > > +}
> > > > +
> > > > +int foo5b(void) // should return 1, returns 0
> > > > +{
> > > > + int n = 0; /* { dg-warning "unused
> > > > variable" } */
> > > > + return (*({
> > > > + int n = 20;
> > > > + char (*x)[n][n] = __builtin_malloc(n * n);
> > > > + (*x)[12][1] = 1;
> > > > + (*x)[0][1] = 0;
> > > > + x;
> > > > + }))[12][1];
> > > > +}
> > > > +
> > > > +int foo5a(void) // should return 1, returns 0
> > > > +{
> > > > + return (*({
> > > > + int n = 20;
> > > > + char (*x)[n][n] = __builtin_malloc(n * n);
> > > > + (*x)[12][1] = 1;
> > > > + (*x)[0][1] = 0;
> > > > + x;
> > > > + }))[12][1];
> > > > +}
> > > > +
> > > > +
> > > > +
> > > > +
> > > > +int main()
> > > > +{
> > > > + if (sizeof(int[10]) != foo3b())
> > > > + __builtin_abort();
> > > > +
> > > > + if (1 != foo4())
> > > > + __builtin_abort();
> > > > +
> > > > + if (400 != foo5c())
> > > > + __builtin_abort();
> > > > +
> > > > + if (1 != foo5a())
> > > > + __builtin_abort();
> > > > +
> > > > + if (1 != foo5b()) // -O0
> > > > + __builtin_abort();
> > > > +
> > > > + if (1 != foo5())
> > > > + __builtin_abort();
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > +
> > > > diff --git a/gcc/testsuite/gcc.dg/vla-stexp-5.c
> > > > b/gcc/testsuite/gcc.dg/vla-stexp-5.c
> > > > new file mode 100644
> > > > index 00000000000..d6a7f2b34b8
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/gcc.dg/vla-stexp-5.c
> > > > @@ -0,0 +1,30 @@
> > > > +/* PR29970 */
> > > > +/* { dg-do run } */
> > > > +/* { dg-options "-Wunused-variable" } */
> > > > +
> > > > +
> > > > +
> > > > +
> > > > +int foo2a(void) // should not ICE
> > > > +{
> > > > + return ({ int n = 20; struct { int x[n];} x; x.x[12] = 1;
> > > > sizeof(x); });
> > > > +}
> > > > +
> > > > +
> > > > +int foo2b(void) // should not ICE
> > > > +{
> > > > + return sizeof *({ int n = 20; struct { int x[n];} x; x.x[12] =
> > > > 1; &x; });
> > > > +}
> > > > +
> > > > +int main()
> > > > +{
> > > > + if (sizeof(struct { int x[20]; }) != foo2a())
> > > > + __builtin_abort();
> > > > +
> > > > + if (sizeof(struct { int x[20]; }) != foo2b())
> > > > + __builtin_abort();
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > +
> > > > diff --git a/gcc/testsuite/gcc.dg/vla-stexp-6.c
> > > > b/gcc/testsuite/gcc.dg/vla-stexp-6.c
> > > > new file mode 100644
> > > > index 00000000000..3d96d38898b
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/gcc.dg/vla-stexp-6.c
> > > > @@ -0,0 +1,94 @@
> > > > +/* PR29970, PR91038 */
> > > > +/* { dg-do run } */
> > > > +/* { dg-options "-O2 -Wunused-variable" } */
> > > > +
> > > > +int foo3b(void) // should not return 0
> > > > +{
> > > > + int n = 0;
> > > > + return sizeof *({ n = 10; int x[n]; &x; });
> > > > +}
> > > > +
> > > > +int foo4(void) // should not ICE
> > > > +{
> > > > + return (*({
> > > > + int n = 20;
> > > > + char (*x)[n][n] = __builtin_malloc(n * n);
> > > > + (*x)[12][1] = 1;
> > > > + x;
> > > > + }))[12][1];
> > > > +}
> > > > +
> > > > +int foo5(void) // should return 1, returns 0
> > > > +{
> > > > + int n = 0;
> > > > + return (*({
> > > > + n = 20;
> > > > + char (*x)[n][n] = __builtin_malloc(n * n);
> > > > + (*x)[12][1] = 1;
> > > > + (*x)[0][1] = 0;
> > > > + x;
> > > > + }))[12][1];
> > > > +}
> > > > +
> > > > +int foo5c(void) // should return 400
> > > > +{
> > > > + int n = 0;
> > > > + return sizeof(*({
> > > > + n = 20;
> > > > + char (*x)[n][n] = __builtin_malloc(n * n);
> > > > + (*x)[12][1] = 1;
> > > > + (*x)[0][1] = 0;
> > > > + x;
> > > > + }));
> > > > +}
> > > > +
> > > > +int foo5b(void) // should return 1, returns 0
> > > > +{
> > > > + int n = 0; /* { dg-warning "unused variable" } */
> > > > + return (*({
> > > > + int n = 20;
> > > > + char (*x)[n][n] = __builtin_malloc(n * n);
> > > > + (*x)[12][1] = 1;
> > > > + (*x)[0][1] = 0;
> > > > + x;
> > > > + }))[12][1];
> > > > +}
> > > > +
> > > > +int foo5a(void) // should return 1, returns 0
> > > > +{
> > > > + return (*({
> > > > + int n = 20;
> > > > + char (*x)[n][n] = __builtin_malloc(n * n);
> > > > + (*x)[12][1] = 1;
> > > > + (*x)[0][1] = 0;
> > > > + x;
> > > > + }))[12][1];
> > > > +}
> > > > +
> > > > +
> > > > +
> > > > +
> > > > +int main()
> > > > +{
> > > > + if (sizeof(int[10]) != foo3b())
> > > > + __builtin_abort();
> > > > +
> > > > + if (1 != foo4())
> > > > + __builtin_abort();
> > > > +
> > > > + if (400 != foo5c())
> > > > + __builtin_abort();
> > > > +
> > > > + if (1 != foo5a())
> > > > + __builtin_abort();
> > > > +
> > > > + if (1 != foo5b()) // -O0
> > > > + __builtin_abort();
> > > > +
> > > > + if (1 != foo5())
> > > > + __builtin_abort();
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > +
> > > > diff --git a/gcc/testsuite/gcc.dg/vla-stexp-7.c
> > > > b/gcc/testsuite/gcc.dg/vla-stexp-7.c
> > > > new file mode 100644
> > > > index 00000000000..3091b9184c2
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/gcc.dg/vla-stexp-7.c
> > > > @@ -0,0 +1,44 @@
> > > > +/* PR91038 */
> > > > +/* { dg-do run } */
> > > > +/* { dg-options "-O2 -Wunused-variable" } */
> > > > +
> > > > +
> > > > +#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
> > > > +
> > > > +struct lbm {
> > > > +
> > > > + int D;
> > > > + const int* DQ;
> > > > +
> > > > +} D2Q9 = { 2,
> > > > + (const int*)&(const int[9][2]){
> > > > + { 0, 0 },
> > > > + { 1, 0 }, { 0, 1 }, { -1, 0 }, { 0, -1 },
> > > > + { 1, 1 }, { -1, 1 }, { -1, -1 }, { 1, -1 },
> > > > + }
> > > > +};
> > > > +
> > > > +void zouhe_left(void)
> > > > +{
> > > > + __auto_type xx = (*({ int N = 2; struct lbm __x = D2Q9; ((const
> > > > int(*)[9][N])__x.DQ); }));
> > > > +
> > > > + if (1 != xx[1][0])
> > > > + __builtin_abort();
> > > > +
> > > > + if (2 != ARRAY_SIZE(xx[1]))
> > > > + __builtin_abort();
> > > > +
> > > > + if (1 != (*({ int N = 2; struct lbm __x = D2Q9; ((const
> > > > int(*)[9][N])__x.DQ);
> > > > }))[1][0])
> > > > + __builtin_abort();
> > > > +
> > > > + if (2 != ARRAY_SIZE(*({ int N = 2; struct lbm __x = D2Q9;
> > > > ((const
> > > > int(*)[9][N])__x.DQ);
> > > > })[1]))
> > > > + __builtin_abort();
> > > > +}
> > > > +
> > > > +int main()
> > > > +{
> > > > + zouhe_left();
> > > > + return 0;
> > > > +}
> > > > +
> > > > +
> > > > diff --git a/gcc/testsuite/gcc.dg/vla-stexp-8.c
> > > > b/gcc/testsuite/gcc.dg/vla-stexp-8.c
> > > > new file mode 100644
> > > > index 00000000000..5b475eb6cf2
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/gcc.dg/vla-stexp-8.c
> > > > @@ -0,0 +1,47 @@
> > > > +/* PR29970, PR91038 */
> > > > +/* { dg-do compile } */
> > > > +/* { dg-options "-O2 -Wunused-variable" } */
> > > > +
> > > > +
> > > > +int foo0(void)
> > > > +{
> > > > + int c = *(*(*({ int n = 10; int (*x)[n][n] =
> > > > __builtin_malloc(sizeof *x); x; }) + 5)
> > > > + 5);
> > > > + return c;
> > > > +}
> > > > +
> > > > +int foo1(void)
> > > > +{
> > > > + int c = *(5 + *(5 + *({ int n = 10; int (*x)[n][n] =
> > > > __builtin_malloc(sizeof *x); x;
> > > > })));
> > > > + return c;
> > > > +}
> > > > +
> > > > +int bar2(void)
> > > > +{
> > > > + int c = (*({ int n = 10; struct { int y[n]; int z; }* x =
> > > > __builtin_malloc(sizeof
> > > > *x); x;
> > > > })).z;
> > > > + return c;
> > > > +}
> > > > +
> > > > +int bar3(void)
> > > > +{
> > > > + int n = 2; /* { dg-warning "unused variable" } */
> > > > + int c = (*({ int n = 3; /* { dg-warning "unused
> > > > variable" } */
> > > > + ({ int n = 10; int (*x)[n][n] = __builtin_malloc(sizeof
> > > > *x); x; });
> > > > }))[5][5];
> > > > + return c;
> > > > +}
> > > > +
> > > > +int bar3b(void)
> > > > +{
> > > > + int n = 2; /* { dg-warning "unused variable" } */
> > > > + int c = (*({ int n = 3; /* { dg-warning "unused
> > > > variable" } */
> > > > + ({ int n = 10; int (*x)[n][n] = __builtin_malloc(sizeof
> > > > *x); x; });
> > > > }))[0][0];
> > > > + return c;
> > > > +}
> > > > +
> > > > +int bar4(void)
> > > > +{
> > > > + int n = 2; /* { dg-warning "unused variable" } */
> > > > + int c = *(5 + *( 5 + *({ int n = 3; /* { dg-warning "unused
> > > > variable" } */
> > > > + ({ int n = 10; int (*x)[n][n] = __builtin_malloc(sizeof
> > > > *x); x; }); })));
> > > > + return c;
> > > > +}
> > > > +
> > > > diff --git a/gcc/testsuite/gcc.dg/vla-stexp-9.c
> > > > b/gcc/testsuite/gcc.dg/vla-stexp-9.c
> > > > new file mode 100644
> > > > index 00000000000..3593a790785
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/gcc.dg/vla-stexp-9.c
> > > > @@ -0,0 +1,53 @@
> > > > +/* PR91038 */
> > > > +/* { dg-do run } */
> > > > +/* { dg-options "-O2 -Wunused-variable" } */
> > > > +
> > > > +
> > > > +
> > > > +void foo(void)
> > > > +{
> > > > + if (2 * sizeof(int) != sizeof((*({ int N = 2; int (*x)[9][N] =
> > > > 0; x; })[1])))
> > > > + __builtin_abort();
> > > > +}
> > > > +
> > > > +void bar(void)
> > > > +{
> > > > + if (2 * sizeof(int) != sizeof((*({ int N = 2; int (*x)[9][N] =
> > > > 0; x; })[0])))
> > > > + __builtin_abort();
> > > > +}
> > > > +
> > > > +void bar0(void)
> > > > +{
> > > > + if (2 * 9 * sizeof(int) != sizeof((*({ int N = 2; int
> > > > (*x)[9][N] = 0; x; }))))
> > > > + __builtin_abort();
> > > > +}
> > > > +
> > > > +void bar11(void)
> > > > +{
> > > > + sizeof(*((*({ int N = 2; int (*x)[9][N] = 0; x; }) + 0)));
> > > > +}
> > > > +
> > > > +void bar12(void)
> > > > +{
> > > > + if (2 * sizeof(int) != sizeof(*((*({ int N = 2; int (*x)[9][N]
> > > > = 0; x; }) ))))
> > > > + __builtin_abort();
> > > > +}
> > > > +
> > > > +void bar1(void)
> > > > +{
> > > > + if (2 * sizeof(int) != sizeof(*((*({ int N = 2; int (*x)[9][N]
> > > > = 0; x; }) + 0))))
> > > > + __builtin_abort();
> > > > +}
> > > > +
> > > > +
> > > > +
> > > > +
> > > > +int main()
> > > > +{
> > > > + foo();
> > > > + bar0();
> > > > + bar12();
> > > > + bar1();
> > > > + bar();
> > > > +}
> > > > +
> > > >
