gallivm: Warn when doing inefficient integer comparisons.

src/gallium/auxiliary/gallivm/lp_bld_logic.c

@@ -92,9 +92,23 @@ lp_build_compare(LLVMBuilderRef builder,
    if(func == PIPE_FUNC_ALWAYS)
       return ones;
 
-   /* TODO: optimize the constant case */
+#if defined(PIPE_ARCH_X86) || defined(PIPE_ARCH_X86_64)
+   /*
+    * There are no unsigned integer comparison instructions in SSE.
+    */
 
-   /* XXX: It is not clear if we should use the ordered or unordered operators */
+   if (!type.floating && !type.sign &&
+       type.width * type.length == 128 &&
+       util_cpu_caps.has_sse2 &&
+       (func == PIPE_FUNC_LESS ||
+        func == PIPE_FUNC_LEQUAL ||
+        func == PIPE_FUNC_GREATER ||
+        func == PIPE_FUNC_GEQUAL) &&
+       (gallivm_debug & GALLIVM_DEBUG_PERF)) {
+         debug_printf("%s: inefficient <%u x i%u> unsigned comparison\n",
+                      __FUNCTION__, type.length, type.width);
+   }
+#endif
 
 #if HAVE_LLVM < 0x0207
 #if defined(PIPE_ARCH_X86) || defined(PIPE_ARCH_X86_64)
@@ -225,6 +239,8 @@ lp_build_compare(LLVMBuilderRef builder,
 #endif
 #endif /* HAVE_LLVM < 0x0207 */
 
+   /* XXX: It is not clear if we should use the ordered or unordered operators */
+
    if(type.floating) {
       LLVMRealPredicate op;
       switch(func) {