gdb/riscv: Improve flen length determination

This solves an assertion failure when a remote provides a target
description which only refers to floating point registers by their
hardware name (e.g. f0), rather than their ABI name (e.g. ft0). GDB
assumed that should the floating point register feature be presented,
it would contain a register called ft0.

The floating point length is now instead determined by searching for
the same register, but looking for any of its aliases.

gdb/ChangeLog:

	* riscv-tdep.c (riscv_gdbarch_init): Support determining flen from
	target descriptions using exclusively floating point register name
	aliases.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index b0b7503b28433e1e42dcc54943ec22f5dbf4e846..a998c5c60dc70862b882ab33af2c1c826d751ad4 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2019-05-22  Simon Cook  <simon.cook@embecosm.com>
+
+       * riscv-tdep.c (riscv_gdbarch_init): Support determining flen from
+       target descriptions using exclusively floating point register name
+       aliases.
+
 2019-05-21  Andrew Burgess  <andrew.burgess@embecosm.com>
 
        PR gdb/18644:

diff --git a/gdb/riscv-tdep.c b/gdb/riscv-tdep.c
index 4fe07ef4375ae1d75dd1551366a1deaec6240d2c..3fc86ab8253d1bbfd014186c06595e68430518f6 100644 (file)
--- a/gdb/riscv-tdep.c
+++ b/gdb/riscv-tdep.c
@@ -3094,7 +3094,21 @@ riscv_gdbarch_init (struct gdbarch_info info,
       valid_p &= riscv_check_tdesc_feature (tdesc_data, feature_fpu,
                                             &riscv_freg_feature);
 
-      int bitsize = tdesc_register_bitsize (feature_fpu, "ft0");
+      /* Search for the first floating point register (by any alias), to
+         determine the bitsize.  */
+      int bitsize = -1;
+      const auto &fp0 = riscv_freg_feature.registers[0];
+
+      for (const char *name : fp0.names)
+       {
+         if (tdesc_unnumbered_register (feature_fpu, name))
+           {
+             bitsize = tdesc_register_bitsize (feature_fpu, name);
+             break;
+           }
+       }
+
+      gdb_assert (bitsize != -1);
       features.flen = (bitsize / 8);
 
       if (riscv_debug_gdbarch)