Hi,
On Wed, Aug 10, 2011 at 04:29:40PM +0200, Richard Guenther wrote:
> On Wed, 10 Aug 2011, Ulrich Weigand wrote:
>
...
> >
> > FAIL: gcc.dg/ipa/ipa-sra-2.c scan-tree-dump eipa_sra "About to replace expr
> > cow_.*D.->red with \\*ISRA"
> > FAIL: gcc.dg/ipa/ipa-sra-2.c scan-tree-dump eipa_sra "About to replace expr
> > cow_.*D.->green with ISRA"
> > FAIL: gcc.dg/ipa/ipa-sra-2.c scan-tree-dump eipa_sra "About to replace expr
> > calf_.*D.->red with \\*ISRA"
> > FAIL: gcc.dg/ipa/ipa-sra-2.c scan-tree-dump eipa_sra "About to replace expr
> > calf_.*D.->green with ISRA"
> > FAIL: gcc.dg/ipa/ipa-sra-6.c scan-tree-dump-times eipa_sra "foo " 1
This has recvently been reported as PR 50052.
...
> >
> > I must admin I continue to be confused about exactly what it is that
> > tree_non_mode_aligned_mem_p is supposed to be testing for. We have:
> >
> > if (TREE_CODE (exp) == SSA_NAME
> > || TREE_CODE (exp) == MEM_REF
> > || mode == BLKmode
> > || is_gimple_min_invariant (exp)
> > || !STRICT_ALIGNMENT)
> > return false;
> >
> > So if we passed in the plain MEM_REF, this would be considered no problem.
> > The COMPONENT_REF does not add any additional misalignment, so one would
> > hope that this also shouldn't be a problem.
> >
> > However, just because there *is* a COMPONENT_REF around it, we suddenly
> > realize the fact that don't have points-to information for the MEM_REF
> > and therefore consider *it* (and consequently the whole COMPONENT_REF)
> > to be potentially misaligned ...
>
> Yep. That's because we are totally confused about alignment :/
>
> Martin, what we need to do is get expands idea of what alignment
> it woudl assume for a handled_component_ref and compare that
> to what it would say if we re-materialize the mem as a MEM_REF.
>
> Unfortunately there isn't a function that you can use to mimic
> expands behavior (that of the normal_inner_ref: case), the closest
> would be to look for TYPE_PACKED or TYPE_ALIGN in addition to
> what get_object_alignment gives us.
>
> Thus something like
>
> align = get_object_alignment (exp);
> if (!TYPE_PACKED (TREE_TYPE (exp))
> && (TREE_CODE (exp) != COMPONENT_REF
> || !DECL_PACKED (TREE_OPERAND (exp, 1))))
> align = MAX (TYPE_ALIGN (TREE_TYPE (exp)), align);
> if (GET_MODE_ALIGNMENT (mode) > align)
> return true;
>
This fixed the failing testcase ipa-sra-2.c but it creates a
misaligned access for the testcase below so I changed it to:
align = get_object_alignment (exp);
if (!TYPE_PACKED (TREE_TYPE (exp)))
{
bool encountered_packed = false;
tree t = exp;
while (TREE_CODE (t) == COMPONENT_REF)
if (DECL_PACKED (TREE_OPERAND (t, 1)))
{
encountered_packed = true;
break;
}
else
t = TREE_OPERAND (t, 0);
if (!encountered_packed)
align = MAX (TYPE_ALIGN (TREE_TYPE (exp)), align);
}
if (GET_MODE_ALIGNMENT (mode) > align)
return true;
I'm currently bootstrapping this on a sparc64 on the compile farm. Is
the patch OK if it passes (it has passed bootstrap and testing on
x86_64-linux but that is no surprise)?
Thanks,
Martin
2011-09-08 Martin Jambor <[email protected]>
PR tree-optimization/50052
* tree-sra.c (tree_non_mode_aligned_mem_p): Look at TYPE_ALIGN if
there is no packed field decl in exp.
* gcc.dg/tree-ssa/pr49094-2.c: New test.
Index: src/gcc/testsuite/gcc.dg/tree-ssa/pr49094-2.c
===================================================================
--- /dev/null
+++ src/gcc/testsuite/gcc.dg/tree-ssa/pr49094-2.c
@@ -0,0 +1,44 @@
+/* { dg-do run } */
+/* { dg-options "-O" } */
+
+struct in_addr {
+ unsigned int s_addr;
+};
+
+struct ip {
+ struct in_addr ip_src,ip_dst;
+ unsigned char ip_p;
+ unsigned short ip_sum;
+};
+
+struct ip2 {
+ unsigned char blah;
+ unsigned short sheep;
+ struct ip ip;
+} __attribute__ ((aligned(1), packed));
+
+struct ip2 ip_fw_fwd_addr;
+
+int test_alignment( char *m )
+{
+ struct ip2 *ip = (struct ip2 *) m;
+ struct in_addr pkt_dst;
+ pkt_dst = ip->ip.ip_dst ;
+ if( pkt_dst.s_addr == 0 )
+ return 1;
+ else
+ return 0;
+}
+
+int __attribute__ ((noinline, noclone))
+intermediary (char *p)
+{
+ return test_alignment (p);
+}
+
+int
+main (int argc, char *argv[])
+{
+ ip_fw_fwd_addr.ip.ip_dst.s_addr = 1;
+ return intermediary ((void *) &ip_fw_fwd_addr);
+}
Index: src/gcc/tree-sra.c
===================================================================
--- src.orig/gcc/tree-sra.c
+++ src/gcc/tree-sra.c
@@ -1086,6 +1086,23 @@ tree_non_mode_aligned_mem_p (tree exp)
return false;
align = get_object_alignment (exp);
+ if (!TYPE_PACKED (TREE_TYPE (exp)))
+ {
+ bool encountered_packed = false;
+ tree t = exp;
+
+ while (TREE_CODE (t) == COMPONENT_REF)
+ if (DECL_PACKED (TREE_OPERAND (t, 1)))
+ {
+ encountered_packed = true;
+ break;
+ }
+ else
+ t = TREE_OPERAND (t, 0);
+
+ if (!encountered_packed)
+ align = MAX (TYPE_ALIGN (TREE_TYPE (exp)), align);
+ }
if (GET_MODE_ALIGNMENT (mode) > align)
return true;
