[Bug c++/78201] New: [7 Regression] ICE in tree_to_shwi, at tree.h:4037 (seen both on ARM32 an AArch64)

["yroux at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78201

            Bug ID: 78201
           Summary: [7 Regression] ICE in tree_to_shwi, at tree.h:4037
                    (seen both on ARM32 an AArch64)
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: yroux at gcc dot gnu.org
  Target Milestone: ---

Created attachment 39959
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=39959&action=edit
Reduced testcase

Hi,

the attached reduced testcase fails with ICE on trunk since r239561.  It was
observed on ARM and AArch64 targets, but might affect targets with
section-anchors enabled.

$ aarch64-linux-gnu-g++ -O2 reduced.C
reduced.C: In function 'void f()':
reduced.C:7:8: internal compiler error: in tree_to_shwi, at tree.c:7313
   char a[e] = "";
        ^
0x1007a32 tree_to_shwi(tree_node const*)
        .../gcc.git~master/gcc/tree.c:7313
0x105bffa default_use_anchors_for_symbol_p(rtx_def const*)
        .../gcc.git~master/gcc/varasm.c:6810
...

The issue is that tree_to_shwi is called without checking its parameter fits in
a signed HOST_WIDE_INT first.  I've validated the following fix, which does the
checking and avoid using section anchors if it fails, on ARM and AArch64
targets, and will submit it on the list.

diff --git a/gcc/varasm.c b/gcc/varasm.c
index 6a7ffc2..231ac05 100644
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -6807,8 +6807,9 @@ default_use_anchors_for_symbol_p (const_rtx symbol)
         anchor range to reduce the amount of instructions require to refer
         to the entire declaration.  */
       if (decl && DECL_SIZE (decl)
-        && tree_to_shwi (DECL_SIZE (decl))
-           >= (targetm.max_anchor_offset * BITS_PER_UNIT))
+         && (!tree_fits_shwi_p (DECL_SIZE (decl))
+             || tree_to_shwi (DECL_SIZE (decl))
+                >= (targetm.max_anchor_offset * BITS_PER_UNIT)))
        return false;