s390: optimize TF to use tmll and fix tmll sim

src/s390/simulator-s390.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stdarg.h>
 #include <stdlib.h>
 #include <cmath>
 
 #if V8_TARGET_ARCH_S390
 
@@ skipping 7761 matching lines @@
 
 EVALUATE(TMLH) {
   UNIMPLEMENTED();
   USE(instr);
   return 0;
 }
 
 EVALUATE(TMLL) {
   DCHECK_OPCODE(TMLL);
   DECODE_RI_A_INSTRUCTION(instr, r1, i2);
-  int mask = i2 & 0x0000FFFF;
-  if (mask == 0) {
-    condition_reg_ = 0x0;
-    return length;
-  }
+  uint32_t mask = i2 & 0x0000FFFF;
   uint32_t r1_val = get_low_register<uint32_t>(r1);
   r1_val = r1_val & 0x0000FFFF;  // uses only the last 16bits
 
-  // Test if all selected bits are Zero
-  bool allSelectedBitsAreZeros = true;
-  for (int i = 0; i < 15; i++) {
-    if (mask & (1 << i)) {
-      if (r1_val & (1 << i)) {
-        allSelectedBitsAreZeros = false;
-        break;
-      }
-    }
-  }
-  if (allSelectedBitsAreZeros) {
+  // Test if all selected bits are zeros or mask is zero
+  if (0 == (mask & r1_val)) {
     condition_reg_ = 0x8;
     return length;  // Done!
   }
 
+  DCHECK(mask != 0);
   // Test if all selected bits are one
-  bool allSelectedBitsAreOnes = true;
-  for (int i = 0; i < 15; i++) {
-    if (mask & (1 << i)) {
-      if (!(r1_val & (1 << i))) {
-        allSelectedBitsAreOnes = false;
-        break;
-      }
-    }
-  }
-  if (allSelectedBitsAreOnes) {
+  if (mask == (mask & r1_val)) {
     condition_reg_ = 0x1;
     return length;  // Done!
   }
 
   // Now we know selected bits mixed zeros and ones
   // Test if the leftmost bit is zero or one
-  for (int i = 14; i >= 0; i--) {
+#if defined(__GNUC__)
+  int leadingZeros = __builtin_clz(mask);
+  mask = 0x80000000u >> leadingZeros;
+  if (mask & r1_val) {
+    // leftmost bit is one
+    condition_reg_ = 0x4;
+  } else {
+    // leftmost bit is zero
+    condition_reg_ = 0x2;
+  }
+  return length;  // Done!
+#else
+  for (int i = 15; i >= 0; i--) {
     if (mask & (1 << i)) {
       if (r1_val & (1 << i)) {
         // leftmost bit is one
         condition_reg_ = 0x2;
       } else {
         // leftmost bit is zero
         condition_reg_ = 0x4;
       }
       return length;  // Done!
     }
   }
+#endif
+  UNREACHABLE();
   return length;
 }
 
 EVALUATE(TMHH) {
   UNIMPLEMENTED();
   USE(instr);
   return 0;
 }
 
 EVALUATE(TMHL) {
@@ skipping 4925 matching lines @@
   return 0;
 }
 
 #undef EVALUATE
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // USE_SIMULATOR
 #endif  // V8_TARGET_ARCH_S390