tree-optimization/88240 - stopgap for floating point code-hoisting issues

diff --git a/gcc/testsuite/gcc.target/i386/pr88240.c b/gcc/testsuite/gcc.target/i386/pr88240.c
new file mode 100644
index 00000000000..5ee02f3193c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr88240.c
@@ -0,0 +1,26 @@ 
+/* { dg-do run } */
+/* { dg-options "-O2 -mno-sse" } */
+
+int flag;
+union { double f; unsigned long long i; } u;
+void __attribute__((noinline))
+init ()
+{
+  flag = 1;
+  u.i = 18442936822990639076ULL;
+}
+unsigned long long __attribute__((noinline))
+test ()
+{
+  if (flag)
+    return u.i;
+  else
+    return u.f;
+}
+int main()
+{
+  init ();
+  if (test () != 18442936822990639076ULL)
+    __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index 0c1654f3580..7d67305bf4b 100644
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -3571,6 +3571,16 @@  do_hoist_insertion (basic_block block)
 	  continue;
 	}
 
+      /* If we end up with a punned expression representation and this
+	 happens to be a float typed one give up - we can't know for
+	 sure whether all paths perform the floating-point load we are
+	 about to insert and on some targets this can cause correctness
+	 issues.  See PR88240.  */
+      if (expr->kind == REFERENCE
+	  && PRE_EXPR_REFERENCE (expr)->punned
+	  && FLOAT_TYPE_P (get_expr_type (expr)))
+	continue;
+
       /* OK, we should hoist this value.  Perform the transformation.  */
       pre_stats.hoist_insert++;
       if (dump_file && (dump_flags & TDF_DETAILS))
diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 2e925a1afbf..934ae40670d 100644
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -3601,6 +3601,7 @@  vn_reference_insert (tree op, tree result, tree vuse, tree vdef)
   vr1->vuse = vuse_ssa_val (vuse);
   vr1->operands = valueize_shared_reference_ops_from_ref (op, &tem).copy ();
   vr1->type = TREE_TYPE (op);
+  vr1->punned = 0;
   ao_ref op_ref;
   ao_ref_init (&op_ref, op);
   vr1->set = ao_ref_alias_set (&op_ref);
@@ -3660,6 +3661,7 @@  vn_reference_insert_pieces (tree vuse, alias_set_type set,
   vr1->vuse = vuse_ssa_val (vuse);
   vr1->operands = valueize_refs (operands);
   vr1->type = type;
+  vr1->punned = 0;
   vr1->set = set;
   vr1->base_set = base_set;
   vr1->hashcode = vn_reference_compute_hash (vr1);
@@ -4892,6 +4894,7 @@  visit_reference_op_call (tree lhs, gcall *stmt)
 	 them here.  */
       vr2->operands = vr1.operands.copy ();
       vr2->type = vr1.type;
+      vr2->punned = vr1.punned;
       vr2->set = vr1.set;
       vr2->base_set = vr1.base_set;
       vr2->hashcode = vr1.hashcode;
@@ -4918,10 +4921,11 @@  visit_reference_op_load (tree lhs, tree op, gimple *stmt)
   bool changed = false;
   tree last_vuse;
   tree result;
+  vn_reference_t res;
 
   last_vuse = gimple_vuse (stmt);
   result = vn_reference_lookup (op, gimple_vuse (stmt),
-				default_vn_walk_kind, NULL, true, &last_vuse);
+				default_vn_walk_kind, &res, true, &last_vuse);
 
   /* We handle type-punning through unions by value-numbering based
      on offset and size of the access.  Be prepared to handle a
@@ -4943,6 +4947,13 @@  visit_reference_op_load (tree lhs, tree op, gimple *stmt)
 	  gimple_match_op res_op (gimple_match_cond::UNCOND,
 				  VIEW_CONVERT_EXPR, TREE_TYPE (op), result);
 	  result = vn_nary_build_or_lookup (&res_op);
+	  if (result
+	      && TREE_CODE (result) == SSA_NAME
+	      && VN_INFO (result)->needs_insertion)
+	    /* Track whether this is the canonical expression for different
+	       typed loads.  We use that as a stopgap measure for code
+	       hoisting when dealing with floating point loads.  */
+	    res->punned = true;
 	}
 
       /* When building the conversion fails avoid inserting the reference
diff --git a/gcc/tree-ssa-sccvn.h b/gcc/tree-ssa-sccvn.h
index d68e7c0ffa3..48701c32544 100644
--- a/gcc/tree-ssa-sccvn.h
+++ b/gcc/tree-ssa-sccvn.h
@@ -145,6 +145,7 @@  typedef struct vn_reference_s
   alias_set_type set;
   alias_set_type base_set;
   tree type;
+  unsigned punned : 1;
   vec<vn_reference_op_s> operands;
   tree result;
   tree result_vdef;