This patch fixes PR48702. IVOPTs does not guarantee that the base
addresses it uses for memory accesses is within the bounds that
the C standard (and the middle-end) would allow. Thus, make sure
that for those bases where we cannot guarantee this we use
TARGET_MEM_REF instead of MEM_REF and relax the middle-end
constraints we put on the base operand of TARGET_MEM_REFs.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2011-05-26 Richard Guenther <rguent...@suse.de>
PR tree-optimization/48702
* tree-ssa-address.c (create_mem_ref_raw): Create MEM_REFs
only when we know the base address is within bounds.
* tree-ssa-alias.c (indirect_ref_may_alias_decl_p): Do not
assume the base address of TARGET_MEM_REFs is in bounds.
* gcc.dg/torture/pr48702.c: New testcase.
Index: gcc/tree-ssa-address.c
===================================================================
--- gcc/tree-ssa-address.c (revision 174179)
+++ gcc/tree-ssa-address.c (working copy)
@@ -361,8 +361,11 @@ create_mem_ref_raw (tree type, tree alia
index2 = addr->base;
}
- /* If possible use a plain MEM_REF instead of a TARGET_MEM_REF. */
- if (alias_ptr_type
+ /* If possible use a plain MEM_REF instead of a TARGET_MEM_REF.
+ ??? As IVOPTs does not follow restrictions to where the base
+ pointer may point to create a MEM_REF only if we know that
+ base is valid. */
+ if (TREE_CODE (base) == ADDR_EXPR
&& (!index2 || integer_zerop (index2))
&& (!addr->index || integer_zerop (addr->index)))
return fold_build2 (MEM_REF, type, base, addr->offset);
Index: gcc/tree-ssa-alias.c
===================================================================
--- gcc/tree-ssa-alias.c (revision 174179)
+++ gcc/tree-ssa-alias.c (working copy)
@@ -744,11 +745,12 @@ indirect_ref_may_alias_decl_p (tree ref1
the pointer access is beyond the extent of the variable access.
(the pointer base cannot validly point to an offset less than zero
of the variable).
- They also cannot alias if the pointer may not point to the decl. */
- if ((TREE_CODE (base1) != TARGET_MEM_REF
- || (!TMR_INDEX (base1) && !TMR_INDEX2 (base1)))
+ ??? IVOPTs creates bases that do not honor this restriction,
+ so do not apply this optimization for TARGET_MEM_REFs. */
+ if (TREE_CODE (base1) != TARGET_MEM_REF
&& !ranges_overlap_p (MAX (0, offset1p), -1, offset2p, max_size2))
return false;
+ /* They also cannot alias if the pointer may not point to the decl. */
if (!ptr_deref_may_alias_decl_p (ptr1, base2))
return false;
Index: gcc/testsuite/gcc.dg/torture/pr48702.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr48702.c (revision 0)
+++ gcc/testsuite/gcc.dg/torture/pr48702.c (revision 0)
@@ -0,0 +1,47 @@
+/* { dg-do run } */
+
+extern void abort (void);
+
+#define LEN 4
+
+static inline void unpack(int array[LEN])
+{
+ int ii, val;
+ val = 1;
+ for (ii = 0; ii < LEN; ii++) {
+ array[ii] = val % 2;
+ val = val / 2;
+ }
+}
+
+static inline int pack(int array[LEN])
+{
+ int ans, ii;
+ ans = 0;
+ for (ii = LEN-1; ii >= 0; ii--) {
+ ans = 2 * ans + array[ii];
+ }
+ return ans;
+}
+
+int __attribute__((noinline))
+foo()
+{
+ int temp, ans;
+ int array[LEN];
+ unpack(array);
+ temp = array[0];
+ array[0] = array[2];
+ array[2] = temp;
+ ans = pack(array);
+ return ans;
+}
+
+int main(void)
+{
+ int val;
+ val = foo();
+ if (val != 4)
+ abort ();
+ return 0;
+}
