[PATCH] Introduce in_inclusive_range, fix -Wtautological-compare warnings

[Simon Marchi]

When compiling with clang or gcc 8, we see warnings like this:

/home/emaisin/src/binutils-gdb/gdb/arm-tdep.c:10013:13: error: comparison of 0 <= unsigned expression is always true [-Werror,-Wtautological-compare]
      if (0 <= insn_op1 && 3 >= insn_op1)
          ~ ^  ~~~~~~~~
/home/emaisin/src/binutils-gdb/gdb/arm-tdep.c:11722:20: error: comparison of unsigned expression >= 0 is always true [-Werror,-Wtautological-compare]
      else if (opB >= 0 && opB <= 2)
               ~~~ ^  ~

This is because an unsigned integer (opB in this case) will always be >=
0.  It is still useful to keep both bounds of the range in the
expression, even if one is at the edge of the data type range.  This
patch introduces a utility function in_inclusive_range that gets rid of
the warning while conveying that we are checking for a range.

Tested by rebuilding.

gdb/ChangeLog:

	* common/common-utils.h (in_inclusive_range): New function.
	* arm-tdep.c (arm_record_extension_space): Use
	in_inclusive_range.
	* cris-tdep.c (cris_spec_reg_applicable): Use
	in_inclusive_range.
---
 gdb/arm-tdep.c            | 4 ++--
 gdb/common/common-utils.h | 9 +++++++++
 gdb/cris-tdep.c           | 4 ++--
 3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index def3958..282efe0 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -10010,7 +10010,7 @@ arm_record_extension_space (insn_decode_record *arm_insn_r)
       && !INSN_RECORDED(arm_insn_r))
     {
       /* Handle MLA(S) and MUL(S).  */
-      if (0 <= insn_op1 && 3 >= insn_op1)
+      if (in_inclusive_range (insn_op1, 0U, 3U))
       {
         record_buf[0] = bits (arm_insn_r->arm_insn, 12, 15);
         record_buf[1] = ARM_PS_REGNUM;
@@ -11719,7 +11719,7 @@ thumb_record_ld_st_reg_offset (insn_decode_record *thumb_insn_r)
           record_buf[0] = reg_src1;
           thumb_insn_r->reg_rec_count = 1;
         }
-      else if (opB >= 0 && opB <= 2)
+      else if (in_inclusive_range (opB, 0U, 2U))
         {
           /* STR(2), STRB(2), STRH(2) .  */
           reg_src1 = bits (thumb_insn_r->arm_insn, 3, 5);
diff --git a/gdb/common/common-utils.h b/gdb/common/common-utils.h
index a32863c..4926a32 100644
--- a/gdb/common/common-utils.h
+++ b/gdb/common/common-utils.h
@@ -125,4 +125,13 @@ extern void free_vector_argv (std::vector<char *> &v);
    joining all the arguments with a whitespace separating them.  */
 extern std::string stringify_argv (const std::vector<char *> &argv);
 
+/* Return true if VALUE is in [LOW, HIGH].  */
+
+template <typename T>
+static bool
+in_inclusive_range (T value, T low, T high)
+{
+  return value >= low && value <= high;
+}
+
 #endif
diff --git a/gdb/cris-tdep.c b/gdb/cris-tdep.c
index d623eb6..209e29f 100644
--- a/gdb/cris-tdep.c
+++ b/gdb/cris-tdep.c
@@ -1434,7 +1434,7 @@ cris_spec_reg_applicable (struct gdbarch *gdbarch,
       /* Indeterminate/obsolete.  */
       return 0;
     case cris_ver_v0_3:
-      return (version >= 0 && version <= 3);
+      return in_inclusive_range (version, 0U, 3U);
     case cris_ver_v3p:
       return (version >= 3);
     case cris_ver_v8:
@@ -1442,7 +1442,7 @@ cris_spec_reg_applicable (struct gdbarch *gdbarch,
     case cris_ver_v8p:
       return (version >= 8);
     case cris_ver_v0_10:
-      return (version >= 0 && version <= 10);
+      return in_inclusive_range (version, 0U, 10U);
     case cris_ver_v3_10:
       return (version >= 3 && version <= 10);
     case cris_ver_v8_10:
-- 
2.7.4