mesa: Make unreachable macro take a string argument.

To aid in debugging.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/glsl/opt_vectorize.cpp

@@ -227,8 +227,7 @@ write_mask_to_swizzle(unsigned write_mask)
    case WRITEMASK_Z: return SWIZZLE_Z;
    case WRITEMASK_W: return SWIZZLE_W;
    }
-   assert(!"not reached");
-   unreachable();
+   unreachable("not reached");
 }
 
 /**

src/mesa/drivers/common/meta.c

@@ -2592,8 +2592,7 @@ _mesa_meta_setup_texture_coords(GLenum faceTarget,
             coord = coords3;
             break;
          default:
-            assert(0);
-            unreachable();
+            unreachable("not reached");
          }
 
          coord[3] = (float) (slice / 6);

src/mesa/drivers/dri/i965/brw_blorp_clear.cpp

@@ -337,9 +337,7 @@ brw_blorp_clear_params::brw_blorp_clear_params(struct brw_context *brw,
             x_scaledown = 2;
             break;
          default:
-            assert(!"Unexpected sample count for fast clear");
-            unreachable();
-            break;
+            unreachable("Unexpected sample count for fast clear");
          }
          y_scaledown = 2;
          x_align = x_scaledown * 2;

src/mesa/drivers/dri/i965/brw_reg.h

@@ -358,9 +358,8 @@ brw_vecn_reg(unsigned width, unsigned file, unsigned nr, unsigned subnr)
    case 16:
       return brw_vec16_reg(file, nr, subnr);
    default:
-      assert(!"Invalid register width");
+      unreachable("Invalid register width");
    }
-   unreachable();
 }
 
 static inline struct brw_reg

src/mesa/drivers/dri/i965/test_vec4_copy_propagation.cpp

@@ -86,8 +86,7 @@ protected:
 
    virtual vec4_instruction *emit_urb_write_opcode(bool complete)
    {
-      assert(!"Not reached");
-      unreachable();
+      unreachable("Not reached");
    }
 };
 

src/mesa/drivers/dri/i965/test_vec4_register_coalesce.cpp

@@ -89,8 +89,7 @@ protected:
 
    virtual vec4_instruction *emit_urb_write_opcode(bool complete)
    {
-      assert(!"Not reached");
-      unreachable();
+      unreachable("Not reached");
    }
 };
 

src/mesa/main/compiler.h

@@ -253,15 +253,23 @@ static INLINE GLuint CPU_TO_LE32(GLuint x)
  * function" warnings.
  */
 #if __GNUC__ >= 4 && __GNUC_MINOR__ >= 5
-#define unreachable() __builtin_unreachable()
+#define unreachable(str)    \
+do {                        \
+   assert(!str);            \
+   __builtin_unreachable(); \
+} while (0)
 #elif (defined(__clang__) && defined(__has_builtin))
 # if __has_builtin(__builtin_unreachable)
-#  define unreachable() __builtin_unreachable()
+#  define unreachable(str)  \
+do {                        \
+   assert(!str);            \
+   __builtin_unreachable(); \
+} while (0)
 # endif
 #endif
 
 #ifndef unreachable
-#define unreachable()
+#define unreachable(str)
 #endif
 
 /*