On Mon, 27 Nov 2017, Richard Biener wrote:
>
> The following is the truly minimal fix for the middle-end issue
> with SRA and memcpy folding interaction. I've tried more variants
> that "make sense" but as they all end up folding slightly more
> memcpy calls than before we run into optimization testcase
> regressions in places that look for __builtin_memcpy and do
> not deal with aggregate copies as MEM[..] = MEM[..];
>
> Bootstrap and regtest running on x86_64-unknown-linux-gnu.
>
> GCC 9 is the time we can try dealing with such fallout, it just
> doesn't feel like the correct time to do now...
Installed as follows, bootstrapped and tested on x86_64-unknown-linux-gnu.
Richard.
2017-11-28 Richard Biener <rguent...@suse.de>
PR middle-end/83141
* gimple-fold.c (gimple_fold_builtin_memory_op): For aggregate
copies generated from memcpy use a character array as reference
type.
Index: gcc/gimple-fold.c
===================================================================
--- gcc/gimple-fold.c (revision 255196)
+++ gcc/gimple-fold.c (working copy)
@@ -1039,8 +1039,24 @@ gimple_fold_builtin_memory_op (gimple_st
gimple_set_vuse (new_stmt, gimple_vuse (stmt));
gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
}
+ new_stmt = gimple_build_assign (destvar, srcvar);
+ goto set_vop_and_replace;
}
- new_stmt = gimple_build_assign (destvar, srcvar);
+
+ /* We get an aggregate copy. Use an unsigned char[] type to
+ perform the copying to preserve padding and to avoid any issues
+ with TREE_ADDRESSABLE types or float modes behavior on copying. */
+ desttype = build_array_type_nelts (unsigned_char_type_node,
+ tree_to_uhwi (len));
+ srctype = desttype;
+ if (src_align > TYPE_ALIGN (srctype))
+ srctype = build_aligned_type (srctype, src_align);
+ if (dest_align > TYPE_ALIGN (desttype))
+ desttype = build_aligned_type (desttype, dest_align);
+ new_stmt
+ = gimple_build_assign (fold_build2 (MEM_REF, desttype, dest, off0),
+ fold_build2 (MEM_REF, srctype, src, off0));
+set_vop_and_replace:
gimple_set_vuse (new_stmt, gimple_vuse (stmt));
gimple_set_vdef (new_stmt, gimple_vdef (stmt));
if (gimple_vdef (new_stmt)
