[gdb/symtab] Workaround PR gas/31115

On arm-linux, with gas 2.40, I run into:
...
(gdb) x /i main+8^M
   0x4e1 <main+7>:      vrhadd.u16      d14, d14, d31^M
(gdb) FAIL: gdb.arch/pr25124.exp: disassemble thumb instruction (1st try)
...

This is a regression due to PR gas/31115, which makes gas produce a low_pc
with the thumb bit set (0x4d8 & 0x1):
...
 <1><24>: Abbrev Number: 2 (DW_TAG_subprogram)
    <25>   DW_AT_name        : main
    <29>   DW_AT_external    : 1
    <29>   DW_AT_type        : <0x2f>
    <2a>   DW_AT_low_pc      : 0x4d9
    <2e>   DW_AT_high_pc     : 12
...

The regression was introduced in 2.39, and is also present in 2.40 and 2.41,
and hasn't been fixed yet.

Work around this in read_func_scope, by using gdbarch_addr_bits_remove on
low_pc and high_pc.

Tested on arm-linux and x86_64-linux.

PR tdep/31453
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31453

1 files changed, 22 insertions, 0 deletions

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 65b1671..7442094 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -148,6 +148,7 @@ static int dwarf2_loclist_block_index;
 static int ada_block_index;
 
 static bool producer_is_gas_lt_2_38 (struct dwarf2_cu *cu);
+static bool producer_is_gas_ge_2_39 (struct dwarf2_cu *cu);
 
 /* Size of .debug_loclists section header for 32-bit DWARF format.  */
 #define LOCLIST_HEADER_SIZE32 12
@@ -9981,6 +9982,15 @@ read_func_scope (struct die_info *die, struct dwarf2_cu *cu)
   lowpc = per_objfile->relocate (unrel_low);
   highpc = per_objfile->relocate (unrel_high);
 
+  if (gdbarch_bfd_arch_info (gdbarch)->arch == bfd_arch_arm
+      && producer_is_gas_ge_2_39 (cu))
+    {
+      /* Gas version 2.39 produces DWARF for a Thumb subprogram with a low_pc
+	 attribute with the thumb bit set (PR gas/31115).  Work around this.  */
+      lowpc = gdbarch_addr_bits_remove (gdbarch, lowpc);
+      highpc = gdbarch_addr_bits_remove (gdbarch, highpc);
+    }
+
   /* If we have any template arguments, then we must allocate a
      different sort of symbol.  */
   for (child_die = die->child; child_die; child_die = child_die->sibling)
@@ -11333,6 +11343,7 @@ check_producer (struct dwarf2_cu *cu)
     {
       cu->producer_is_gas_lt_2_38 = major < 2 || (major == 2 && minor < 38);
       cu->producer_is_gas_2_39 = major == 2 && minor == 39;
+      cu->producer_is_gas_ge_2_40 = major > 2 || (major == 2 && minor >= 40);
     }
   else
     {
@@ -11387,6 +11398,17 @@ producer_is_gas_2_39 (struct dwarf2_cu *cu)
   return cu->producer_is_gas_2_39;
 }
 
+/* Return true if CU is produced by GAS 2.39 or later.  */
+
+static bool
+producer_is_gas_ge_2_39 (struct dwarf2_cu *cu)
+{
+  if (!cu->checked_producer)
+    check_producer (cu);
+
+  return cu->producer_is_gas_2_39 || cu->producer_is_gas_ge_2_40;
+}
+
 /* Return the accessibility of DIE, as given by DW_AT_accessibility.
    If that attribute is not available, return the appropriate
    default.  */