Bump up precision size to 16 bits.

The new __dmr type that is being added as a possible future PowerPC instruction
set bumps into a structure field size issue.  The size of the __dmr type is 1024 bits.
The precision field in tree_type_common is currently 10 bits, so if you store
1,024 into field, you get a 0 back.  When you get 0 in the precision field, the
ccp pass passes this 0 to sext_hwi in hwint.h.  That function in turn generates
a shift that is equal to the host wide int bit size, which is undefined as
machine dependent for shifting in C/C++.

      int shift = HOST_BITS_PER_WIDE_INT - prec;
      return ((HOST_WIDE_INT) ((unsigned HOST_WIDE_INT) src << shift)) >> shift;

It turns out the x86_64 where I first did my tests returns the original input
before the two shifts, while the PowerPC always returns 0.  In the ccp pass, the
original input is -1, and so it worked.  When I did the runs on the PowerPC, the
result was 0, which ultimately led to the failure.

2023-02-01  Richard Biener  <rguenther@suse.de>
	    Michael Meissner  <meissner@linux.ibm.com>

	PR middle-end/108623
	* tree-core.h (tree_type_common): Bump up precision field to 16 bits.
	Align bit fields > 1 bit to at least an 8-bit boundary.

diff --git a/gcc/tree-core.h b/gcc/tree-core.h
index 847f0b1e9943c35a3adf89d550290934633623eb..a1aea136e752cbeba7b164cadb71c07782547391 100644 (file)
--- a/gcc/tree-core.h
+++ b/gcc/tree-core.h
@@ -1680,18 +1680,8 @@ struct GTY(()) tree_type_common {
   tree attributes;
   unsigned int uid;
 
-  unsigned int precision : 10;
-  unsigned no_force_blk_flag : 1;
-  unsigned needs_constructing_flag : 1;
-  unsigned transparent_aggr_flag : 1;
-  unsigned restrict_flag : 1;
-  unsigned contains_placeholder_bits : 2;
-
+  unsigned int precision : 16;
   ENUM_BITFIELD(machine_mode) mode : 8;
-
-  /* TYPE_STRING_FLAG for INTEGER_TYPE and ARRAY_TYPE.
-     TYPE_CXX_ODR_P for RECORD_TYPE and UNION_TYPE.  */
-  unsigned string_flag : 1;
   unsigned lang_flag_0 : 1;
   unsigned lang_flag_1 : 1;
   unsigned lang_flag_2 : 1;
@@ -1707,12 +1697,22 @@ struct GTY(()) tree_type_common {
      so we need to store the value 32 (not 31, as we need the zero
      as well), hence six bits.  */
   unsigned align : 6;
+  /* TYPE_STRING_FLAG for INTEGER_TYPE and ARRAY_TYPE.
+     TYPE_CXX_ODR_P for RECORD_TYPE and UNION_TYPE.  */
+  unsigned string_flag : 1;
+  unsigned no_force_blk_flag : 1;
+
   unsigned warn_if_not_align : 6;
+  unsigned needs_constructing_flag : 1;
+  unsigned transparent_aggr_flag : 1;
+
+  unsigned contains_placeholder_bits : 2;
+  unsigned restrict_flag : 1;
   unsigned typeless_storage : 1;
   unsigned empty_flag : 1;
   unsigned indivisible_p : 1;
   unsigned no_named_args_stdarg_p : 1;
-  unsigned spare : 15;
+  unsigned spare : 9;
 
   alias_set_type alias_set;
   tree pointer_to;