Set mode of decimal floats before calling layout_type

Previously decimal floating-point types were created and laid
out as binary floating-point types, then the caller changed
the mode to a decimal mode later.  The problem with that
approach is that not all targets support an equivalent binary
floating-point mode.  When they didn't, we would give the
type BLKmode and lay it out as a zero-sized type.

This probably had no effect in practice.  If a target doesn't
support a binary mode then it's unlikely to support the decimal
equivalent either.  However, with the stricter mode checking
added by later patches, we would assert if a scalar floating-
point type didn't have a scalar floating-point mode.

gcc/
2016-11-16  Richard Sandiford  <richard.sandiford@arm.com>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

	* stor-layout.c (layout_type): Allow the caller to set the mode of
	a float type.  Only choose one here if the mode is still VOIDmode.
	* tree.c (build_common_tree_nodes): Set the type mode of decimal
	floats before calling layout_type.
	* config/rs6000/rs6000.c (rs6000_init_builtins): Likewise.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r242862

4 files changed, 20 insertions, 7 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index efc2016..5c8e785 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,4 +1,14 @@
 2016-11-25  Richard Sandiford  <richard.sandiford@arm.com>
+	    Alan Hayward  <alan.hayward@arm.com>
+	    David Sherwood  <david.sherwood@arm.com>
+
+	* stor-layout.c (layout_type): Allow the caller to set the mode of
+	a float type.  Only choose one here if the mode is still VOIDmode.
+	* tree.c (build_common_tree_nodes): Set the type mode of decimal
+	floats before calling layout_type.
+	* config/rs6000/rs6000.c (rs6000_init_builtins): Likewise.
+
+2016-11-25  Richard Sandiford  <richard.sandiford@arm.com>
 
 	* tree-tailcall.c (find_tail_calls): Allow calls to reference
 	local variables if all references are known to be direct.
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 7cf71e6..fce4e39 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -16792,8 +16792,8 @@ rs6000_init_builtins (void)
     {
       ibm128_float_type_node = make_node (REAL_TYPE);
       TYPE_PRECISION (ibm128_float_type_node) = 128;
-      layout_type (ibm128_float_type_node);
       SET_TYPE_MODE (ibm128_float_type_node, IFmode);
+      layout_type (ibm128_float_type_node);
 
       lang_hooks.types.register_builtin_type (ibm128_float_type_node,
 					      "__ibm128");
@@ -16812,8 +16812,8 @@ rs6000_init_builtins (void)
     {
       ieee128_float_type_node = make_node (REAL_TYPE);
       TYPE_PRECISION (ibm128_float_type_node) = 128;
-      layout_type (ieee128_float_type_node);
       SET_TYPE_MODE (ieee128_float_type_node, KFmode);
+      layout_type (ieee128_float_type_node);
 
       /* If we are not exporting the __float128/_Float128 keywords, we need a
 	 keyword to get the types created.  Use __ieee128 as the dummy
diff --git a/gcc/stor-layout.c b/gcc/stor-layout.c
index 9f8efcb..5a4bcf1 100644
--- a/gcc/stor-layout.c
+++ b/gcc/stor-layout.c
@@ -2135,8 +2135,11 @@ layout_type (tree type)
       break;
 
     case REAL_TYPE:
-      SET_TYPE_MODE (type,
-		     mode_for_size (TYPE_PRECISION (type), MODE_FLOAT, 0));
+      /* Allow the caller to choose the type mode, which is how decimal
+	 floats are distinguished from binary ones.  */
+      if (TYPE_MODE (type) == VOIDmode)
+	SET_TYPE_MODE (type,
+		       mode_for_size (TYPE_PRECISION (type), MODE_FLOAT, 0));
       TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
       TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
       break;
diff --git a/gcc/tree.c b/gcc/tree.c
index 11e0abc..dd6ef63 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -10436,20 +10436,20 @@ build_common_tree_nodes (bool signed_char)
   /* Decimal float types. */
   dfloat32_type_node = make_node (REAL_TYPE);
   TYPE_PRECISION (dfloat32_type_node) = DECIMAL32_TYPE_SIZE;
-  layout_type (dfloat32_type_node);
   SET_TYPE_MODE (dfloat32_type_node, SDmode);
+  layout_type (dfloat32_type_node);
   dfloat32_ptr_type_node = build_pointer_type (dfloat32_type_node);
 
   dfloat64_type_node = make_node (REAL_TYPE);
   TYPE_PRECISION (dfloat64_type_node) = DECIMAL64_TYPE_SIZE;
-  layout_type (dfloat64_type_node);
   SET_TYPE_MODE (dfloat64_type_node, DDmode);
+  layout_type (dfloat64_type_node);
   dfloat64_ptr_type_node = build_pointer_type (dfloat64_type_node);
 
   dfloat128_type_node = make_node (REAL_TYPE);
   TYPE_PRECISION (dfloat128_type_node) = DECIMAL128_TYPE_SIZE;
-  layout_type (dfloat128_type_node);
   SET_TYPE_MODE (dfloat128_type_node, TDmode);
+  layout_type (dfloat128_type_node);
   dfloat128_ptr_type_node = build_pointer_type (dfloat128_type_node);
 
   complex_integer_type_node = build_complex_type (integer_type_node, true);