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

[Simon Marchi <simon.marchi@ericsson.com>]

On 2017-10-30 12:05 PM, John Baldwin wrote:
> It may be sufficient to just be consistent within a function?  In arm-tdep.c
> it is two instances in separate functions whereas for cris-tdep.c it is
> multiple instances in the same function which is what stuck out to me.

In arm-tdep.c, I ended changing the other instances in the functions that were
already touched by the patch, for consistency.  This is what I pushed:


commit b020ff8074af22639e3f3c0f700f45d067521249
Author: Simon Marchi <simon.marchi@ericsson.com>
Date:   Mon Oct 30 14:27:30 2017 -0400

    Introduce in_inclusive_range, fix -Wtautological-compare warnings

    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.
    	(thumb_record_ld_st_reg_offset): Use in_inclusive_range.
    	* cris-tdep.c (cris_spec_reg_applicable): Use
    	in_inclusive_range.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 2855f4d..5a680ed 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,12 @@
+2017-10-30  Simon Marchi  <simon.marchi@ericsson.com>
+
+	* common/common-utils.h (in_inclusive_range): New function.
+	* arm-tdep.c (arm_record_extension_space): Use
+	in_inclusive_range.
+	(thumb_record_ld_st_reg_offset): Use in_inclusive_range.
+	* cris-tdep.c (cris_spec_reg_applicable): Use
+	in_inclusive_range.
+
 2017-10-30  Pedro Alves  <palves@redhat.com>
 	    Simon Marchi <simon.marchi@ericsson.com>

diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index def3958..46b7888 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -10010,13 +10010,13 @@ 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;
         arm_insn_r->reg_rec_count = 2;
       }
-      else if (4 <= insn_op1 && 15 >= insn_op1)
+      else if (in_inclusive_range (insn_op1, 4U, 15U))
       {
         /* Handle SMLAL(S), SMULL(S), UMLAL(S), UMULL(S).  */
         record_buf[0] = bits (arm_insn_r->arm_insn, 16, 19);
@@ -11712,14 +11712,14 @@ thumb_record_ld_st_reg_offset (insn_decode_record *thumb_insn_r)
       /* Handle load/store register offset.  */
       uint32_t opB = bits (thumb_insn_r->arm_insn, 9, 11);

-      if (opB >= 4 && opB <= 7)
+      if (in_inclusive_range (opB, 4U, 7U))
         {
           /* LDR(2), LDRB(2) , LDRH(2), LDRSB, LDRSH.  */
           reg_src1 = bits (thumb_insn_r->arm_insn,0, 2);
           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..416843f 100644
--- a/gdb/cris-tdep.c
+++ b/gdb/cris-tdep.c
@@ -1434,19 +1434,19 @@ 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:
-      return (version == 8 || version == 9);
+      return in_inclusive_range (version, 8U, 9U);
     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);
+      return in_inclusive_range (version, 3U, 10U);
     case cris_ver_v8_10:
-      return (version >= 8 && version <= 10);
+      return in_inclusive_range (version, 8U, 10U);
     case cris_ver_v10:
       return (version == 10);
     case cris_ver_v10p: