PR middle-end/82569

	* tree-outof-ssa.h (always_initialized_rtx_for_ssa_name_p): Delete.
	* expr.c (expand_expr_real_1) <expand_decl_rtl>: Revert latest change.
	* loop-iv.c (iv_get_reaching_def): Likewise.
	* cfgexpand.c (expand_one_ssa_partition): Initialize the RTX if the 
	variable is promoted and the partition contains undefined values.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@254037 138bc75d-0d04-0410-961f-82ee72b054a4

5 files changed, 26 insertions, 40 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 63f84f52f71..f42428c57f2 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2017-10-24  Eric Botcazou  <ebotcazou@adacore.com>
+
+	PR middle-end/82569
+	* tree-outof-ssa.h (always_initialized_rtx_for_ssa_name_p): Delete.
+	* expr.c (expand_expr_real_1) <expand_decl_rtl>: Revert latest change.
+	* loop-iv.c (iv_get_reaching_def): Likewise.
+	* cfgexpand.c (expand_one_ssa_partition): Initialize the RTX if the 
+	variable is promoted and the partition contains undefined values.
+
 2017-10-23  Sandra Loosemore  <sandra@codesourcery.com>
 
 	* config/nios2/nios2.c (nios2_rtx_costs): Make costs better
diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index 00efe141213..ec8c8459d12 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -1391,10 +1391,18 @@ expand_one_ssa_partition (tree var)
     }
 
   machine_mode reg_mode = promote_ssa_mode (var, NULL);
-
   rtx x = gen_reg_rtx (reg_mode);
 
   set_rtl (var, x);
+
+  /* For a promoted variable, X will not be used directly but wrapped in a
+     SUBREG with SUBREG_PROMOTED_VAR_P set, which means that the RTL land
+     will assume that its upper bits can be inferred from its lower bits.
+     Therefore, if X isn't initialized on every path from the entry, then
+     we must do it manually in order to fulfill the above assumption.  */
+  if (reg_mode != TYPE_MODE (TREE_TYPE (var))
+      && bitmap_bit_p (SA.partitions_for_undefined_values, part))
+    emit_move_insn (x, CONST0_RTX (reg_mode));
 }
 
 /* Record the association between the RTL generated for partition PART
diff --git a/gcc/expr.c b/gcc/expr.c
index cdf7ca2cf5c..496d492c9fa 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -9912,43 +9912,24 @@ expand_expr_real_1 (tree exp, rtx target, machine_mode tmode,
 	  && GET_MODE (decl_rtl) != dmode)
 	{
 	  machine_mode pmode;
-	  bool always_initialized_rtx;
 
 	  /* Get the signedness to be used for this variable.  Ensure we get
 	     the same mode we got when the variable was declared.  */
 	  if (code != SSA_NAME)
-	    {
-	      pmode = promote_decl_mode (exp, &unsignedp);
-	      always_initialized_rtx = true;
-	    }
+	    pmode = promote_decl_mode (exp, &unsignedp);
 	  else if ((g = SSA_NAME_DEF_STMT (ssa_name))
 		   && gimple_code (g) == GIMPLE_CALL
 		   && !gimple_call_internal_p (g))
-	    {
-	      pmode = promote_function_mode (type, mode, &unsignedp,
-					    gimple_call_fntype (g), 2);
-	      always_initialized_rtx
-		= always_initialized_rtx_for_ssa_name_p (ssa_name);
-	    }
+	    pmode = promote_function_mode (type, mode, &unsignedp,
+					   gimple_call_fntype (g),
+					   2);
 	  else
-	    {
-	      pmode = promote_ssa_mode (ssa_name, &unsignedp);
-	      always_initialized_rtx
-		= always_initialized_rtx_for_ssa_name_p (ssa_name);
-	    }
-
+	    pmode = promote_ssa_mode (ssa_name, &unsignedp);
 	  gcc_assert (GET_MODE (decl_rtl) == pmode);
 
 	  temp = gen_lowpart_SUBREG (mode, decl_rtl);
-
-	  /* We cannot assume anything about an existing extension if the
-	     register may contain uninitialized bits.  */
-	  if (always_initialized_rtx)
-	    {
-	      SUBREG_PROMOTED_VAR_P (temp) = 1;
-	      SUBREG_PROMOTED_SET (temp, unsignedp);
-	    }
-
+	  SUBREG_PROMOTED_VAR_P (temp) = 1;
+	  SUBREG_PROMOTED_SET (temp, unsignedp);
 	  return temp;
 	}
 
diff --git a/gcc/loop-iv.c b/gcc/loop-iv.c
index 45e822980ff..1d0c66f2b2f 100644
--- a/gcc/loop-iv.c
+++ b/gcc/loop-iv.c
@@ -353,7 +353,7 @@ iv_get_reaching_def (rtx_insn *insn, rtx reg, df_ref *def)
   adef = DF_REF_CHAIN (use)->ref;
 
   /* We do not handle setting only part of the register.  */
-  if (DF_REF_FLAGS (adef) & (DF_REF_READ_WRITE | DF_REF_SUBREG))
+  if (DF_REF_FLAGS (adef) & DF_REF_READ_WRITE)
     return GRD_INVALID;
 
   def_insn = DF_REF_INSN (adef);
diff --git a/gcc/tree-outof-ssa.h b/gcc/tree-outof-ssa.h
index 1220b6256ca..ebbaea1a03e 100644
--- a/gcc/tree-outof-ssa.h
+++ b/gcc/tree-outof-ssa.h
@@ -74,18 +74,6 @@ get_gimple_for_ssa_name (tree exp)
   return NULL;
 }
 
-/* Return whether the RTX expression representing the storage of the outof-SSA
-   partition that the SSA name EXP is a member of is always initialized.  */
-static inline bool
-always_initialized_rtx_for_ssa_name_p (tree exp)
-{
-  int p = partition_find (SA.map->var_partition, SSA_NAME_VERSION (exp));
-  if (SA.map->partition_to_view)
-    p = SA.map->partition_to_view[p];
-  gcc_assert (p != NO_PARTITION);
-  return !bitmap_bit_p (SA.partitions_for_undefined_values, p);
-}
-
 extern bool ssa_is_replaceable_p (gimple *stmt);
 extern void finish_out_of_ssa (struct ssaexpand *sa);
 extern unsigned int rewrite_out_of_ssa (struct ssaexpand *sa);