PowerPC: fix _Float128 type output string

PowerPC supports two 128-bit floating point formats, the IBM long double
and IEEE 128-bit float.  The issue is the DWARF information does not
distinguish between the two.  There have been proposals of how to extend
the DWARF information as discussed in

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104194

but has not been fully implemented.

GCC introduced the _Float128 internal type as a work around for the issue.
The workaround is not transparent to GDB.  The internal _Float128 type
name is printed rather then the user specified long double type.  This
patch adds a new gdbarch method to allow PowerPC to detect the GCC
workaround.  The workaround checks for "_Float128" name when reading the
base typedef from the die_info.  If the workaround is detected, the type
and format fields from the _Float128 typedef are copied to the long
double typedef.  The same is done for the complex long double typedef.

This patch fixes 74 regression test failures in
gdb.base/whatis-ptype-typedefs.exp on PowerPC with IEEE float 128 as the
default on GCC.  It fixes one regression test failure in
gdb.base/complex-parts.exp.

The patch has been tested on Power 10 where GCC defaults to IEEE Float
128-bit and on Power 10 where GCC defaults to the IBM 128-bit float.  The
patch as also been tested on X86-64 with no new regression failures.

1 files changed, 23 insertions, 0 deletions

diff --git a/gdb/gdbarch_components.py b/gdb/gdbarch_components.py
index 9f0430c7770..a0e35b8b5e8 100644
--- a/gdb/gdbarch_components.py
+++ b/gdb/gdbarch_components.py
@@ -901,6 +901,29 @@ May return 0 when unable to determine that address.""",
     invalid=False,
 )
 
+
+# The DWARF info currently does not distinquish between IEEE 128-bit floating
+# point values and the IBM 128-bit floating point format.  GCC has an internal
+# hack to identify the IEEE 128-bit floating point value.  The long double is a
+# defined base type in C.  The GCC hack uses a typedef for long double to
+# reference_Float128 base to identify the long double as and IEEE 128-bit
+# value.  The following method is used to "fix" the long double type to be a
+# base type with the IEEE float format info from the _Float128 basetype and
+# the long double name.  With the fix, the proper name is printed for the
+# GDB typedef command.
+Function(
+    comment="""
+Return true if the typedef record needs to be replaced.".
+
+Return 0 by default""",
+    type="bool",
+    name="dwarf2_omit_typedef_p",
+    params=[("struct type *", "target_type"), ("const char *", "producer"),
+            ("const char *", "name")],
+    predefault="default_dwarf2_omit_typedef_p",
+    invalid=False,
+)
+
 Method(
     comment="""
 Return true if the return value of function is stored in the first hidden