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.
In addition, once the precision field is larger, it will help PR C/102989 (C2x
_BigInt) as well as the implementation of the SET_TYPE_VECTOR_SUBPARTS macro.
I bootstraped various PowerPC compilers (power10 LE, power9 LE, power8 BE)
along with an x86_64 build. There were no regressions. My proposed patches
for the __dmr type now run fine. Can I install this into the master branch for
GCC 13?
2023-02-02 Richard Biener <rguent...@suse.de>
Michael Meissner <meiss...@linux.ibm.com>
gcc/
PR middle-end/108623
* hwint.h (sext_hwi): Add assertion against precision 0.
* 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.
---
gcc/hwint.h | 1 +
gcc/tree-core.h | 24 ++++++++++++------------
2 files changed, 13 insertions(+), 12 deletions(-)
diff --git a/gcc/hwint.h b/gcc/hwint.h
index e31aa006fa4..ba92efbfc25 100644
--- a/gcc/hwint.h
+++ b/gcc/hwint.h
@@ -277,6 +277,7 @@ ctz_or_zero (unsigned HOST_WIDE_INT x)
static inline HOST_WIDE_INT
sext_hwi (HOST_WIDE_INT src, unsigned int prec)
{
+ gcc_checking_assert (prec != 0);
if (prec == HOST_BITS_PER_WIDE_INT)
return src;
else
diff --git a/gcc/tree-core.h b/gcc/tree-core.h
index 8124a1328d4..b71748c6c02 100644
--- a/gcc/tree-core.h
+++ b/gcc/tree-core.h
@@ -1686,18 +1686,8 @@ 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;
@@ -1713,12 +1703,22 @@ 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;
--
2.39.1
--
Michael Meissner, IBM
PO Box 98, Ayer, Massachusetts, USA, 01432
email: meiss...@linux.ibm.com
