The following fixes the testcase in PR66142 Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard. 2015-05-26 Richard Biener <rguent...@suse.de> PR tree-optimization/66142 * tree-ssa-sccvn.c (vn_reference_lookup_3): Manually compare MEM_REFs for the same base address. * gcc.dg/tree-ssa/ssa-fre-44.c: New testcase. Index: gcc/tree-ssa-sccvn.c =================================================================== --- gcc/tree-ssa-sccvn.c (revision 223574) +++ gcc/tree-ssa-sccvn.c (working copy) @@ -1894,7 +1894,12 @@ vn_reference_lookup_3 (ao_ref *ref, tree size2 = lhs_ref.size; maxsize2 = lhs_ref.max_size; if (maxsize2 == -1 - || (base != base2 && !operand_equal_p (base, base2, 0)) + || (base != base2 + && (TREE_CODE (base) != MEM_REF + || TREE_CODE (base2) != MEM_REF + || TREE_OPERAND (base, 0) != TREE_OPERAND (base2, 0) + || !tree_int_cst_equal (TREE_OPERAND (base, 1), + TREE_OPERAND (base2, 1)))) || offset2 > offset || offset2 + size2 < offset + maxsize) return (void *)-1; Index: gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-44.c =================================================================== --- gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-44.c (revision 0) +++ gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-44.c (working copy) @@ -0,0 +1,62 @@ +/* { dg-do compile } */ +/* { dg-options "-O -fdump-tree-fre1" } */ + +struct A { float x, y; }; +struct B { struct A u; }; +void bar (struct A *); + +float +f1 (struct B *x, int y) +{ + struct A p; + p.x = 1.0f; + p.y = 2.0f; + struct A *q = &x[y].u; + *q = p; + float f = x[y].u.x + x[y].u.y; + bar (&p); + return f; +} + +float +f2 (struct B *x, int y) +{ + struct A p; + p.x = 1.0f; + p.y = 2.0f; + x[y].u = p; + float f = x[y].u.x + x[y].u.y; + bar (&p); + return f; +} + +float +f3 (struct B *x, int y) +{ + struct A p; + p.x = 1.0f; + p.y = 2.0f; + struct A *q = &x[y].u; + __builtin_memcpy (&q->x, &p.x, sizeof (float)); + __builtin_memcpy (&q->y, &p.y, sizeof (float)); + *q = p; + float f = x[y].u.x + x[y].u.y; + bar (&p); + return f; +} + +float +f4 (struct B *x, int y) +{ + struct A p; + p.x = 1.0f; + p.y = 2.0f; + __builtin_memcpy (&x[y].u.x, &p.x, sizeof (float)); + __builtin_memcpy (&x[y].u.y, &p.y, sizeof (float)); + float f = x[y].u.x + x[y].u.y; + bar (&p); + return f; +} + +/* { dg-final { scan-tree-dump-times "return 3.0" 4 "fre1" } } */ +/* { dg-final { cleanup-tree-dump "fre1" } } */