Re: [patch] workaround gcc46: prologue skip skips too far (PR 12435) #2

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

On Thu, 08 Sep 2011 19:15:59 +0200, Doug Evans wrote:
> These kinds of functions tend to grow and grow and become hard to maintain.
> IWBN if all this new code is about a specific issue then tuck it away
> in its own function.

I agree it is a good improvement.


> > + Â/* At least GCC 4.6.0 and 4.6.1 can produce invalid false prologue and marker
> > + Â Â on amd64. ÂThis flag is set independently of the symtab arch. Â*/
> > +
> > + Âunsigned amd64_prologue_line_bug : 1;
> 
> I can hear the screams of pushback if a random net person wanted to
> check in anything architecture specific to the architecture
> independent part of gdb. :-)

That is a good comment.  There is also symtab->producer, not just cu->producer
so it is not needed at all.

I will check it in.


Thanks,
Jan


gdb/
2011-09-08  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Code cleanup.
	* amd64-tdep.c (amd64_skip_prologue): Move the XMM code to ...
	(amd64_skip_xmm_prologue): ... this new function.  Describe its
	parameters.  No longer use amd64_prologue_line_bug.
	* defs.h (producer_is_gcc_ge_4): New declaration.
	* dwarf2read.c (producer_is_gcc_ge_4): Move to utils.c.
	(process_full_comp_unit): Update its caller.  Remove
	amd64_prologue_line_bug initialization.
	* symtab.h (struct symtab): Remove field amd64_prologue_line_bug.
	* utils.c (producer_is_gcc_ge_4): Moved here from dwarf2read.c.

--- a/gdb/amd64-tdep.c
+++ b/gdb/amd64-tdep.c
@@ -1910,43 +1910,37 @@ amd64_analyze_prologue (struct gdbarch *gdbarch,
   return pc;
 }
 
-/* Return PC of first real instruction.  */
+/* Work around false termination of prologue - GCC PR debug/48827.
+
+   START_PC is the first instruction of a function, PC is its minimal already
+   determined advanced address.  Function returns PC if it has nothing to do.
+
+   84 c0                test   %al,%al
+   74 23                je     after
+   <-- here is 0 lines advance - the false prologue end marker.
+   0f 29 85 70 ff ff ff movaps %xmm0,-0x90(%rbp)
+   0f 29 4d 80          movaps %xmm1,-0x80(%rbp)
+   0f 29 55 90          movaps %xmm2,-0x70(%rbp)
+   0f 29 5d a0          movaps %xmm3,-0x60(%rbp)
+   0f 29 65 b0          movaps %xmm4,-0x50(%rbp)
+   0f 29 6d c0          movaps %xmm5,-0x40(%rbp)
+   0f 29 75 d0          movaps %xmm6,-0x30(%rbp)
+   0f 29 7d e0          movaps %xmm7,-0x20(%rbp)
+   after:  */
 
 static CORE_ADDR
-amd64_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR start_pc)
+amd64_skip_xmm_prologue (CORE_ADDR pc, CORE_ADDR start_pc)
 {
-  struct amd64_frame_cache cache;
-  CORE_ADDR pc;
   struct symtab_and_line start_pc_sal, next_sal;
   gdb_byte buf[4 + 8 * 7];
   int offset, xmmreg;
 
-  amd64_init_frame_cache (&cache);
-  pc = amd64_analyze_prologue (gdbarch, start_pc, 0xffffffffffffffffLL,
-			       &cache);
-  if (cache.frameless_p)
-    return start_pc;
-
-  /* GCC PR debug/48827 produced false prologue end:
-     84 c0                test   %al,%al
-     74 23                je     after
-     <-- here is 0 lines advance - the false prologue end marker.
-     0f 29 85 70 ff ff ff movaps %xmm0,-0x90(%rbp)
-     0f 29 4d 80          movaps %xmm1,-0x80(%rbp)
-     0f 29 55 90          movaps %xmm2,-0x70(%rbp)
-     0f 29 5d a0          movaps %xmm3,-0x60(%rbp)
-     0f 29 65 b0          movaps %xmm4,-0x50(%rbp)
-     0f 29 6d c0          movaps %xmm5,-0x40(%rbp)
-     0f 29 75 d0          movaps %xmm6,-0x30(%rbp)
-     0f 29 7d e0          movaps %xmm7,-0x20(%rbp)
-     after:  */
-
   if (pc == start_pc)
     return pc;
 
   start_pc_sal = find_pc_sect_line (start_pc, NULL, 0);
   if (start_pc_sal.symtab == NULL
-      || !start_pc_sal.symtab->amd64_prologue_line_bug
+      || producer_is_gcc_ge_4 (start_pc_sal.symtab->producer) < 6
       || start_pc_sal.pc != start_pc || pc >= start_pc_sal.end)
     return pc;
 
@@ -1993,6 +1987,23 @@ amd64_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR start_pc)
 
   return next_sal.end;
 }
+
+/* Return PC of first real instruction.  */
+
+static CORE_ADDR
+amd64_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR start_pc)
+{
+  struct amd64_frame_cache cache;
+  CORE_ADDR pc;
+
+  amd64_init_frame_cache (&cache);
+  pc = amd64_analyze_prologue (gdbarch, start_pc, 0xffffffffffffffffLL,
+			       &cache);
+  if (cache.frameless_p)
+    return start_pc;
+
+  return amd64_skip_xmm_prologue (pc, start_pc);
+}
 
 
 /* Normal frames.  */
--- a/gdb/defs.h
+++ b/gdb/defs.h
@@ -431,6 +431,8 @@ extern int parse_pid_to_attach (char *args);
 
 extern struct cleanup *make_bpstat_clear_actions_cleanup (void);
 
+extern int producer_is_gcc_ge_4 (const char *producer);
+
 /* From demangle.c */
 
 extern void set_demangling_style (char *);
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -4723,50 +4723,6 @@ compute_delayed_physnames (struct dwarf2_cu *cu)
     }
 }
 
-/* Check for GCC >= 4.x.  Return minor version (x) of 4.x in such case.  If it
-   is not GCC or it is GCC older than 4.x return -1.  If it is GCC 5.x or
-   higher return INT_MAX.  */
-
-static int
-producer_is_gcc_ge_4 (struct dwarf2_cu *cu)
-{
-  const char *cs;
-  int major, minor;
-
-  if (cu->producer == NULL)
-    {
-      /* For unknown compilers expect their behavior is not compliant.  For GCC
-	 this case can also happen for -gdwarf-4 type units supported since
-	 gcc-4.5.  */
-
-      return -1;
-    }
-
-  /* Skip any identifier after "GNU " - such as "C++" or "Java".  */
-
-  if (strncmp (cu->producer, "GNU ", strlen ("GNU ")) != 0)
-    {
-      /* For non-GCC compilers expect their behavior is not compliant.  */
-
-      return -1;
-    }
-  cs = &cu->producer[strlen ("GNU ")];
-  while (*cs && !isdigit (*cs))
-    cs++;
-  if (sscanf (cs, "%d.%d", &major, &minor) != 2)
-    {
-      /* Not recognized as GCC.  */
-
-      return -1;
-    }
-
-  if (major < 4)
-    return -1;
-  if (major > 4)
-    return INT_MAX;
-  return minor;
-}
-
 /* Generate full symbol information for PST and CU, whose DIEs have
    already been loaded into memory.  */
 
@@ -4806,7 +4762,7 @@ process_full_comp_unit (struct dwarf2_per_cu_data *per_cu)
 
   if (symtab != NULL)
     {
-      int gcc_4_minor = producer_is_gcc_ge_4 (cu);
+      int gcc_4_minor = producer_is_gcc_ge_4 (cu->producer);
 
       /* Set symtab language to language from DW_AT_language.  If the
 	 compilation is from a C file generated by language preprocessors, do
@@ -4829,9 +4785,6 @@ process_full_comp_unit (struct dwarf2_per_cu_data *per_cu)
 
       if (gcc_4_minor >= 5)
 	symtab->epilogue_unwind_valid = 1;
-
-      if (gcc_4_minor >= 6)
-	symtab->amd64_prologue_line_bug = 1;
     }
 
   if (dwarf2_per_objfile->using_index)
--- a/gdb/symtab.h
+++ b/gdb/symtab.h
@@ -784,11 +784,6 @@ struct symtab
 
   unsigned int epilogue_unwind_valid : 1;
 
-  /* At least GCC 4.6.0 and 4.6.1 can produce invalid false prologue and marker
-     on amd64.  This flag is set independently of the symtab arch.  */
-
-  unsigned amd64_prologue_line_bug : 1;
-
   /* The macro table for this symtab.  Like the blockvector, this
      may be shared between different symtabs --- and normally is for
      all the symtabs in a given compilation unit.  */
--- a/gdb/utils.c
+++ b/gdb/utils.c
@@ -3691,6 +3691,50 @@ make_bpstat_clear_actions_cleanup (void)
   return make_cleanup (do_bpstat_clear_actions_cleanup, NULL);
 }
 
+/* Check for GCC >= 4.x according to the symtab->producer string.  Return minor
+   version (x) of 4.x in such case.  If it is not GCC or it is GCC older than
+   4.x return -1.  If it is GCC 5.x or higher return INT_MAX.  */
+
+int
+producer_is_gcc_ge_4 (const char *producer)
+{
+  const char *cs;
+  int major, minor;
+
+  if (producer == NULL)
+    {
+      /* For unknown compilers expect their behavior is not compliant.  For GCC
+	 this case can also happen for -gdwarf-4 type units supported since
+	 gcc-4.5.  */
+
+      return -1;
+    }
+
+  /* Skip any identifier after "GNU " - such as "C++" or "Java".  */
+
+  if (strncmp (producer, "GNU ", strlen ("GNU ")) != 0)
+    {
+      /* For non-GCC compilers expect their behavior is not compliant.  */
+
+      return -1;
+    }
+  cs = &producer[strlen ("GNU ")];
+  while (*cs && !isdigit (*cs))
+    cs++;
+  if (sscanf (cs, "%d.%d", &major, &minor) != 2)
+    {
+      /* Not recognized as GCC.  */
+
+      return -1;
+    }
+
+  if (major < 4)
+    return -1;
+  if (major > 4)
+    return INT_MAX;
+  return minor;
+}
+
 /* Provide a prototype to silence -Wmissing-prototypes.  */
 extern initialize_file_ftype _initialize_utils;