[binutils-gdb] Fix bug in nios2 prologue analysis.

[Sandra Loosemore]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=de8af80891ff0eee61cd219b316e176e9ae88e91

commit de8af80891ff0eee61cd219b316e176e9ae88e91
Author: Sandra Loosemore <sandra@codesourcery.com>
Date:   Fri Aug 23 08:18:54 2019 -0700

    Fix bug in nios2 prologue analysis.
    
    The nios2 prologue analyzer was mistakenly using an unsigned int field
    to represent a 32-bit signed value.  This caused problems with an
    incorrect conversion being applied to negative values when they were
    automatically promoted for addition to a 64-bit CORE_ADDR value.
    
    This patch fixes test failures in gdb.base/large-frame.exp and
    gdb.dwarf2/dw2-ref-missing-frame.exp.  Normally the nios2 backend
    prefers to use the dwarf2 unwinder so the prologue analyzer is only
    invoked if there is no dwarf2 information.
    
    2019-08-23  Sandra Loosemore  <sandra@codesourcery.com>
    
    	gdb/
    	* nios2-tdep.c (struct reg_value): Improve comments.  Make
    	the offset field signed.

Diff:
---
 gdb/ChangeLog    | 5 +++++
 gdb/nios2-tdep.c | 8 +++++---
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index ac84245..df8488b 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2019-08-23  Sandra Loosemore  <sandra@codesourcery.com>
+
+	* nios2-tdep.c (struct reg_value): Improve comments.  Make
+	the offset field signed.
+
 2019-08-22  Christian Biesinger  <cbiesinger@google.com>
 
 	* python/lib/gdb/__init__.py (_execute_file): New function.
diff --git a/gdb/nios2-tdep.c b/gdb/nios2-tdep.c
index 2a21c33..8d685d4 100644
--- a/gdb/nios2-tdep.c
+++ b/gdb/nios2-tdep.c
@@ -58,13 +58,15 @@ static int nios2_debug = 0;
    analysis; see the reg_value and reg_saved tables in
    struct nios2_unwind_cache, respectively.  */
 
-/* struct reg_value is used to record that a register has the same value
-   as reg at the given offset from the start of a function.  */
+/* struct reg_value is used to record that a register has reg's initial
+   value at the start of a function plus the given constant offset.
+   If reg == 0, then the value is just the offset.
+   If reg < 0, then the value is unknown.  */
 
 struct reg_value
 {
   int reg;
-  unsigned int offset;
+  int offset;
 };
 
 /* struct reg_saved is used to record that a register value has been saved at