[gcc r12-7560] middle-end/104786 - ICE with asm and VLA

[Richard Biener <rguenth@gcc.gnu.org>]

https://gcc.gnu.org/g:ba3ff5e35144e2afff4ccef4ccbbbbaba9870afb

commit r12-7560-gba3ff5e35144e2afff4ccef4ccbbbbaba9870afb
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Mar 9 10:55:49 2022 +0100

    middle-end/104786 - ICE with asm and VLA
    
    The following fixes an ICE observed with a MEM_REF allows_mem asm
    operand referencing a VLA.  The following makes sure to not attempt
    to go the temporary creation way when we cannot.
    
    2022-03-09  Richard Biener  <rguenther@suse.de>
    
            PR middle-end/104786
            * cfgexpand.cc (expand_asm_stmt): Do not generate a copy
            for VLAs without an upper size bound.
    
            * gcc.dg/pr104786.c: New testcase.

Diff:
---
 gcc/cfgexpand.cc                | 4 +++-
 gcc/testsuite/gcc.dg/pr104786.c | 8 ++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/gcc/cfgexpand.cc b/gcc/cfgexpand.cc
index 87536ec7ccd..4f99f040450 100644
--- a/gcc/cfgexpand.cc
+++ b/gcc/cfgexpand.cc
@@ -3297,7 +3297,9 @@ expand_asm_stmt (gasm *stmt)
 		    && GET_MODE (DECL_RTL (val)) != TYPE_MODE (type)))
 	  || ! allows_reg
 	  || is_inout
-	  || TREE_ADDRESSABLE (type))
+	  || TREE_ADDRESSABLE (type)
+	  || (!tree_fits_poly_int64_p (TYPE_SIZE (type))
+	      && !known_size_p (max_int_size_in_bytes (type))))
 	{
 	  op = expand_expr (val, NULL_RTX, VOIDmode,
 			    !allows_reg ? EXPAND_MEMORY : EXPAND_WRITE);
diff --git a/gcc/testsuite/gcc.dg/pr104786.c b/gcc/testsuite/gcc.dg/pr104786.c
new file mode 100644
index 00000000000..3076d236d21
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr104786.c
@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+/* { dg-options "-std=gnu90" } */
+
+void h(void *di, int num)
+{
+  char (*t)[num] = di;
+  __asm__ ("" : "=X"( *t));
+}