Change the utils WhichPowerOf2 function to use a simpler algorithm.

src/arm/macro-assembler-arm.cc

Index: src/arm/macro-assembler-arm.cc
===================================================================
--- src/arm/macro-assembler-arm.cc	(revision 5768)
+++ src/arm/macro-assembler-arm.cc	(working copy)
@@ -220,20 +220,20 @@
 
 void MacroAssembler::And(Register dst, Register src1, const Operand& src2,
                          Condition cond) {
-  if (!CpuFeatures::IsSupported(ARMv7) || src2.is_single_instruction()) {
+  if (!src2.is_reg() &&
+      !src2.must_use_constant_pool() &&
+      src2.immediate() == 0) {
+    mov(dst, Operand(0, RelocInfo::NONE), LeaveCC, cond);
+
+  } else if (!src2.is_single_instruction() &&
+             !src2.must_use_constant_pool() &&
+             CpuFeatures::IsSupported(ARMv7) &&
+             IsPowerOf2(src2.immediate() + 1)) {
+    ubfx(dst, src1, 0, WhichPowerOf2(src2.immediate() + 1), cond);
+
+  } else {
     and_(dst, src1, src2, LeaveCC, cond);
-    return;
   }
-  int32_t immediate = src2.immediate();
-  if (immediate == 0) {
-    mov(dst, Operand(0, RelocInfo::NONE), LeaveCC, cond);
-    return;
-  }
-  if (IsPowerOf2(immediate + 1) && ((immediate & 1) != 0)) {
-    ubfx(dst, src1, 0, WhichPowerOf2(immediate + 1), cond);
-    return;
-  }
-  and_(dst, src1, src2, LeaveCC, cond);
 }