The VIEW_CONVERT_EXPR expansion path fails to handle the case where
we promote alignment for !STRICT_ALIGNMENT targets but for modes
that are supposed to be handled by movmisalign.
This is exposed in gcc.dg/torture/pr45678-2.c on i?86 when
you apply the candidate patch for PR50444 in comment #15.
I'm now bootstrapping and regtesting this as a prerequesite.
Richard.
2012-01-23 Richard Guenther <rguent...@suse.de>
PR tree-optimization/50444
* expr.c (expand_expr_real_1): Properly expand VIEW_CONVERT_EXPR
to an aligned mode from unaligned memory using movmisalign.
Index: gcc/expr.c
===================================================================
--- gcc/expr.c (revision 183423)
+++ gcc/expr.c (working copy)
@@ -10044,10 +10044,24 @@ expand_expr_real_1 (tree exp, rtx target
results. */
if (MEM_P (op0))
{
+ enum insn_code icode;
+
op0 = copy_rtx (op0);
if (TYPE_ALIGN_OK (type))
set_mem_align (op0, MAX (MEM_ALIGN (op0), TYPE_ALIGN (type)));
+ else if (mode != BLKmode
+ && MEM_ALIGN (op0) < GET_MODE_ALIGNMENT (mode)
+ && ((icode = optab_handler (movmisalign_optab, mode))
+ != CODE_FOR_nothing))
+ {
+ struct expand_operand ops[2];
+ PUT_MODE (op0, mode);
+ create_output_operand (&ops[0], NULL_RTX, mode);
+ create_fixed_operand (&ops[1], op0);
+ expand_insn (icode, 2, ops);
+ return ops[0].value;
+ }
else if (STRICT_ALIGNMENT
&& mode != BLKmode
&& MEM_ALIGN (op0) < GET_MODE_ALIGNMENT (mode))
