Re: [PATCH 2/2] c/100547 - reject overly large vector_size attributes

[Martin Sebor via Gcc-patches]

On 5/12/21 2:47 AM, Richard Biener wrote:

This rejects a number of vector components that does not fit an 'int'
which is an internal limitation of RTVEC.

This regresses gcc.dg/attr-vector_size.c which checks for much larger
supported vectors.  Not sure what to do about this - I'll also note
the RTVEC limitation is a host specific limitation (unless we change
this 'int' to int32_t).

Bootstrapped and tested on x86_64-unknown-linux-gnu with the above
mentioned regression.

Any comments?

Just a few minor ones.

Thanks,
Richard.

2021-05-12  Richard Biener  <rguent...@suse.de>

        PR c/100547
gcc/c-family/
        * c-attribs.c (type_valid_for_vector_size): Reject too large nunits.

        * gcc.dg/pr100547.c: New testcase.
---
  gcc/c-family/c-attribs.c        | 10 ++++++++++
  gcc/testsuite/gcc.dg/pr100547.c | 35 +++++++++++++++++++++++++++++++++
  2 files changed, 45 insertions(+)
  create mode 100644 gcc/testsuite/gcc.dg/pr100547.c

diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
index c1f652d1dc9..60bcfa22df1 100644
--- a/gcc/c-family/c-attribs.c
+++ b/gcc/c-family/c-attribs.c
@@ -4252,6 +4252,16 @@ type_valid_for_vector_size (tree type, tree atname, tree 
args,
        return NULL_TREE;
      }

+ if (nunits >= (unsigned HOST_WIDE_INT)INT_MAX)

The inequality includes INT_MAX, so the phrasing below doesn't exactly
match the condition.  Since nunits must be a power of 2 the condition
might as well be greater than.

+    {
+      if (error_p)
+       error ("number of components of the vector exceeds %d", INT_MAX);

"number of vector components" sounds better (though there are other
messages that use this phrasing already).

Especially since it's computed, I would suggest to mention the value
of nunits in the message (it should also be mentioned in the "power
of two" message).

Martin

+      else
+       warning (OPT_Wattributes,
+                "number of components of the vector exceeds %d", INT_MAX);
+      return NULL_TREE;
+    }
+
    if (ptrnunits)
      *ptrnunits = nunits;

diff --git a/gcc/testsuite/gcc.dg/pr100547.c b/gcc/testsuite/gcc.dg/pr100547.c

new file mode 100644
index 00000000000..92f34bf974f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr100547.c
@@ -0,0 +1,35 @@
+/* { dg-do compile } */
+/* { dg-options "-O -g" } */
+
+typedef int __attribute__((vector_size(
+    ((((((((((((((((((((((((((((((8 * sizeof(short)) * sizeof(short)) *
+                                sizeof(short)) *
+                               sizeof(short)) *
+                              sizeof(short)) *
+                             sizeof(short)) *
+                            sizeof(short)) *
+                           sizeof(short)) *
+                          sizeof(short)) *
+                         sizeof(short)) *
+                        sizeof(short)) *
+                       sizeof(short)) *
+                      sizeof(short)) *
+                     sizeof(short)) *
+                    sizeof(short)) *
+                   sizeof(short)) *
+                  sizeof(short)) *
+                 sizeof(short)) *
+                sizeof(short)) *
+               sizeof(short)) *
+              sizeof(short)) *
+             sizeof(short)) *
+            sizeof(short)) *
+           sizeof(short)) *
+          sizeof(short)) *
+         sizeof(short)) *
+        sizeof(short)) *
+       sizeof(short)) *
+      sizeof(short)) *
+     sizeof(short)) *
+    sizeof(short)))) V; /* { dg-error "number of components" } */
+void k() { V w = { 0 }; }