re PR target/63679 ([AArch64] Failure to constant fold.)

2014-11-24  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/63679
	* tree-ssa-sccvn.c: Include ipa-ref.h, plugin-api.h and cgraph.h.
	(copy_reference_ops_from_ref): Fix non-constant ADDR_EXPR case
	to properly leave off at -1.
	(fully_constant_vn_reference_p): Generalize folding from
	constant initializers.
	(vn_reference_lookup_3): When looking through aggregate copies
	handle offsetted reads and try simplifying the result to
	a constant.
	* gimple-fold.h (fold_ctor_reference): Export.
	* gimple-fold.c (fold_ctor_reference): Likewise.

	* gcc.dg/tree-ssa/ssa-fre-42.c: New testcase.
	* gcc.dg/tree-ssa/20030807-5.c: Avoid folding read from global to zero.
	* gcc.target/i386/ssetype-1.c: Likewise.
	* gcc.target/i386/ssetype-3.c: Likewise.
	* gcc.target/i386/ssetype-5.c: Likewise.

From-SVN: r218019

10 files changed, 159 insertions, 30 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e362f1d..cadd82f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,17 @@
+2014-11-24  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/63679
+	* tree-ssa-sccvn.c: Include ipa-ref.h, plugin-api.h and cgraph.h.
+	(copy_reference_ops_from_ref): Fix non-constant ADDR_EXPR case
+	to properly leave off at -1.
+	(fully_constant_vn_reference_p): Generalize folding from
+	constant initializers.
+	(vn_reference_lookup_3): When looking through aggregate copies
+	handle offsetted reads and try simplifying the result to
+	a constant.
+	* gimple-fold.h (fold_ctor_reference): Export.
+	* gimple-fold.c (fold_ctor_reference): Likewise.
+
 2014-11-24  Petr Murzin  <petr.murzin@intel.com>
 
 	* simplify-rtx.c (simplify_ternary_operation): Simplify
diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
index 91b9b0c..98ec117 100644
--- a/gcc/gimple-fold.c
+++ b/gcc/gimple-fold.c
@@ -4788,10 +4788,6 @@ gimple_fold_stmt_to_constant (gimple stmt, tree (*valueize) (tree))
 /* The following set of functions are supposed to fold references using
    their constant initializers.  */
 
-static tree fold_ctor_reference (tree type, tree ctor,
-				 unsigned HOST_WIDE_INT offset,
-				 unsigned HOST_WIDE_INT size, tree);
-
 /* See if we can find constructor defining value of BASE.
    When we know the consructor with constant offset (such as
    base is array[40] and we do know constructor of array), then
@@ -5027,7 +5023,7 @@ fold_nonarray_ctor_reference (tree type, tree ctor,
 /* CTOR is value initializing memory, fold reference of type TYPE and size SIZE
    to the memory at bit OFFSET.  */
 
-static tree
+tree
 fold_ctor_reference (tree type, tree ctor, unsigned HOST_WIDE_INT offset,
 		     unsigned HOST_WIDE_INT size, tree from_decl)
 {
diff --git a/gcc/gimple-fold.h b/gcc/gimple-fold.h
index a38848f..7574de8 100644
--- a/gcc/gimple-fold.h
+++ b/gcc/gimple-fold.h
@@ -39,6 +39,8 @@ extern tree follow_single_use_edges (tree);
 extern tree gimple_fold_stmt_to_constant_1 (gimple, tree (*) (tree),
 					    tree (*) (tree) = no_follow_ssa_edges);
 extern tree gimple_fold_stmt_to_constant (gimple, tree (*) (tree));
+extern tree fold_ctor_reference (tree, tree, unsigned HOST_WIDE_INT,
+				 unsigned HOST_WIDE_INT, tree);
 extern tree fold_const_aggregate_ref_1 (tree, tree (*) (tree));
 extern tree fold_const_aggregate_ref (tree);
 extern tree gimple_get_virt_method_for_binfo (HOST_WIDE_INT, tree,
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index a9ac86b..7db895b 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,12 @@
+2014-11-24  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/63679
+	* gcc.dg/tree-ssa/ssa-fre-42.c: New testcase.
+	* gcc.dg/tree-ssa/20030807-5.c: Avoid folding read from global to zero.
+	* gcc.target/i386/ssetype-1.c: Likewise.
+	* gcc.target/i386/ssetype-3.c: Likewise.
+	* gcc.target/i386/ssetype-5.c: Likewise.
+
 2014-11-24  Jonathan Wakely  <jwakely@redhat.com>
 	    Paolo Carlini  <paolo.carlini@oracle.com>
 
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/20030807-5.c b/gcc/testsuite/gcc.dg/tree-ssa/20030807-5.c
index 424b558..2397644 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/20030807-5.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/20030807-5.c
@@ -13,7 +13,7 @@ struct rtx_def
   unsigned int unchanging:1;
 
 };
-static rtx current_sym_addr;
+rtx current_sym_addr;
 
 int
 foo ()
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-42.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-42.c
new file mode 100644
index 0000000..c90bb0d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-42.c
@@ -0,0 +1,34 @@
+/* { dg-do run } */
+/* { dg-require-alias "" } */
+/* { dg-options "-O -fdump-tree-fre1" } */
+
+extern void abort (void);
+
+struct X { int a[128]; };
+static const struct X a = { 0, 1, 2, 3 };
+/* Prevent gimplify_modify_expr_rhs / gimplify_init_constructor from
+   expanding the aggregate copy below inline.  */
+static const struct X A __attribute__((alias("a")));
+struct X *q;
+int __attribute__((noinline))
+foo ()
+{
+  struct X b = A;
+  int *p = &b.a[2];
+  /* Prevent SRA from decomposing b.  */
+  q = &b;
+  return *p;
+}
+
+int main()
+{
+  if (foo() != 2)
+    abort ();
+  return 0;
+}
+
+/* Verify the aggregate copy we want to look through is still in place.  */
+/* { dg-final { scan-tree-dump "b = A;" "fre1" } } */
+/* Verify we have propagated the element read all the way to the return.  */
+/* { dg-final { scan-tree-dump "return 2" "fre1" } } */
+/* { dg-final { cleanup-tree-dump "fre1" } } */
diff --git a/gcc/testsuite/gcc.target/i386/ssetype-1.c b/gcc/testsuite/gcc.target/i386/ssetype-1.c
index 36dcaf6..34185dd 100644
--- a/gcc/testsuite/gcc.target/i386/ssetype-1.c
+++ b/gcc/testsuite/gcc.target/i386/ssetype-1.c
@@ -14,7 +14,7 @@
 
 #include <xmmintrin.h>
 
-static __m128d magic_a, magic_b;
+__m128d magic_a, magic_b;
 
 __m128d
 t1(void)
diff --git a/gcc/testsuite/gcc.target/i386/ssetype-3.c b/gcc/testsuite/gcc.target/i386/ssetype-3.c
index d6887d5..c2eff2b 100644
--- a/gcc/testsuite/gcc.target/i386/ssetype-3.c
+++ b/gcc/testsuite/gcc.target/i386/ssetype-3.c
@@ -13,7 +13,7 @@
 
 #include <xmmintrin.h>
 
-static __m128 magic_a, magic_b;
+__m128 magic_a, magic_b;
 __m128
 t1(void)
 {
diff --git a/gcc/testsuite/gcc.target/i386/ssetype-5.c b/gcc/testsuite/gcc.target/i386/ssetype-5.c
index bc903f5..2dd2de4 100644
--- a/gcc/testsuite/gcc.target/i386/ssetype-5.c
+++ b/gcc/testsuite/gcc.target/i386/ssetype-5.c
@@ -13,7 +13,7 @@
 /* Verify that we generate proper instruction with memory operand.  */
 
 #include <xmmintrin.h>
-static __m128i magic_a, magic_b;
+__m128i magic_a, magic_b;
 __m128i
 t1(void)
 {
diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index aa155a8..8b3f2c7 100644
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -65,6 +65,9 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-ssa-sccvn.h"
 #include "tree-cfg.h"
 #include "domwalk.h"
+#include "ipa-ref.h"
+#include "plugin-api.h"
+#include "cgraph.h"
 
 /* This algorithm is based on the SCC algorithm presented by Keith
    Cooper and L. Taylor Simpson in "SCC-Based Value numbering"
@@ -920,7 +923,7 @@ copy_reference_ops_from_ref (tree ref, vec<vn_reference_op_s> *result)
 	      temp.op0 = ref;
 	      break;
 	    }
-	  /* Fallthrough.  */
+	  break;
 	  /* These are only interesting for their operands, their
 	     existence, and their type.  They will never be the last
 	     ref in the chain of references (IE they require an
@@ -1325,24 +1328,66 @@ fully_constant_vn_reference_p (vn_reference_t ref)
 	}
     }
 
-  /* Simplify reads from constant strings.  */
-  else if (op->opcode == ARRAY_REF
-	   && TREE_CODE (op->op0) == INTEGER_CST
-	   && integer_zerop (op->op1)
-	   && operands.length () == 2)
+  /* Simplify reads from constants or constant initializers.  */
+  else if (BITS_PER_UNIT == 8
+	   && is_gimple_reg_type (ref->type)
+	   && (!INTEGRAL_TYPE_P (ref->type)
+	       || TYPE_PRECISION (ref->type) % BITS_PER_UNIT == 0))
     {
-      vn_reference_op_t arg0;
-      arg0 = &operands[1];
-      if (arg0->opcode == STRING_CST
-	  && (TYPE_MODE (op->type)
-	      == TYPE_MODE (TREE_TYPE (TREE_TYPE (arg0->op0))))
-	  && GET_MODE_CLASS (TYPE_MODE (op->type)) == MODE_INT
-	  && GET_MODE_SIZE (TYPE_MODE (op->type)) == 1
-	  && tree_int_cst_sgn (op->op0) >= 0
-	  && compare_tree_int (op->op0, TREE_STRING_LENGTH (arg0->op0)) < 0)
-	return build_int_cst_type (op->type,
-				   (TREE_STRING_POINTER (arg0->op0)
-				    [TREE_INT_CST_LOW (op->op0)]));
+      HOST_WIDE_INT off = 0;
+      HOST_WIDE_INT size = tree_to_shwi (TYPE_SIZE (ref->type));
+      if (size % BITS_PER_UNIT != 0
+	  || size > MAX_BITSIZE_MODE_ANY_MODE)
+	return NULL_TREE;
+      size /= BITS_PER_UNIT;
+      unsigned i;
+      for (i = 0; i < operands.length (); ++i)
+	{
+	  if (operands[i].off == -1)
+	    return NULL_TREE;
+	  off += operands[i].off;
+	  if (operands[i].opcode == MEM_REF)
+	    {
+	      ++i;
+	      break;
+	    }
+	}
+      vn_reference_op_t base = &operands[--i];
+      tree ctor = error_mark_node;
+      tree decl = NULL_TREE;
+      if (TREE_CODE_CLASS (base->opcode) == tcc_constant)
+	ctor = base->op0;
+      else if (base->opcode == MEM_REF
+	       && base[1].opcode == ADDR_EXPR
+	       && (TREE_CODE (TREE_OPERAND (base[1].op0, 0)) == VAR_DECL
+		   || TREE_CODE (TREE_OPERAND (base[1].op0, 0)) == CONST_DECL))
+	{
+	  decl = TREE_OPERAND (base[1].op0, 0);
+	  ctor = ctor_for_folding (decl);
+	}
+      if (ctor == NULL_TREE)
+	return build_zero_cst (ref->type);
+      else if (ctor != error_mark_node)
+	{
+	  if (decl)
+	    {
+	      tree res = fold_ctor_reference (ref->type, ctor,
+					      off * BITS_PER_UNIT,
+					      size * BITS_PER_UNIT, decl);
+	      if (res)
+		{
+		  STRIP_USELESS_TYPE_CONVERSION (res);
+		  if (is_gimple_min_invariant (res))
+		    return res;
+		}
+	    }
+	  else
+	    {
+	      unsigned char buf[MAX_BITSIZE_MODE_ANY_MODE / BITS_PER_UNIT];
+	      if (native_encode_expr (ctor, buf, size, off) > 0)
+		return native_interpret_expr (ref->type, buf, size);
+	    }
+	}
     }
 
   return NULL_TREE;
@@ -1850,11 +1895,20 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *vr_,
 	 may fail when comparing types for compatibility.  But we really
 	 don't care here - further lookups with the rewritten operands
 	 will simply fail if we messed up types too badly.  */
+      HOST_WIDE_INT extra_off = 0;
       if (j == 0 && i >= 0
 	  && lhs_ops[0].opcode == MEM_REF
-	  && lhs_ops[0].off != -1
-	  && (lhs_ops[0].off == vr->operands[i].off))
-	i--, j--;
+	  && lhs_ops[0].off != -1)
+	{
+	  if (lhs_ops[0].off == vr->operands[i].off)
+	    i--, j--;
+	  else if (vr->operands[i].opcode == MEM_REF
+		   && vr->operands[i].off != -1)
+	    {
+	      extra_off = vr->operands[i].off - lhs_ops[0].off;
+	      i--, j--;
+	    }
+	}
 
       /* i now points to the first additional op.
 	 ???  LHS may not be completely contained in VR, one or more
@@ -1865,6 +1919,20 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *vr_,
 
       /* Now re-write REF to be based on the rhs of the assignment.  */
       copy_reference_ops_from_ref (gimple_assign_rhs1 (def_stmt), &rhs);
+
+      /* Apply an extra offset to the inner MEM_REF of the RHS.  */
+      if (extra_off != 0)
+	{
+	  if (rhs.length () < 2
+	      || rhs[0].opcode != MEM_REF
+	      || rhs[0].off == -1)
+	    return (void *)-1;
+	  rhs[0].off += extra_off;
+	  rhs[0].op0 = int_const_binop (PLUS_EXPR, rhs[0].op0,
+					build_int_cst (TREE_TYPE (rhs[0].op0),
+						       extra_off));
+	}
+
       /* We need to pre-pend vr->operands[0..i] to rhs.  */
       vec<vn_reference_op_s> old = vr->operands;
       if (i + 1 + rhs.length () > vr->operands.length ())
@@ -1882,6 +1950,12 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *vr_,
 	shared_lookup_references = vr->operands;
       vr->hashcode = vn_reference_compute_hash (vr);
 
+      /* Try folding the new reference to a constant.  */
+      tree val = fully_constant_vn_reference_p (vr);
+      if (val)
+	return vn_reference_lookup_or_insert_for_pieces
+		 (vuse, vr->set, vr->type, vr->operands, val);
+
       /* Adjust *ref from the new operands.  */
       if (!ao_ref_init_from_vn_reference (&r, vr->set, vr->type, vr->operands))
 	return (void *)-1;