Revise assertions and fix bug in the implementation of shifts

runtime/vm/intermediate_language_arm.cc

Index: runtime/vm/intermediate_language_arm.cc
diff --git a/runtime/vm/intermediate_language_arm.cc b/runtime/vm/intermediate_language_arm.cc
index af4b0fe6cee5e539c187f551053ed3ab595626a2..995c1cd866cb947eb2d25850a61dac94d9bcb201 100644
--- a/runtime/vm/intermediate_language_arm.cc
+++ b/runtime/vm/intermediate_language_arm.cc
@@ -6546,9 +6546,7 @@ void ShiftMintOpInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
     ASSERT(locs()->in(1).constant().IsSmi());
     const int32_t shift =
         reinterpret_cast<int32_t>(locs()->in(1).constant().raw()) >> 1;

[Vyacheslav Egorov (Google), 2017/07/12 09:44:48]

this should better be

Smi::Cast().Value()

instead of such manual untagging. 

[alexmarkov, 2017/07/12 16:47:36]

Done, in the follow-up CL https://codereview.chromium.org/2975073002/

-    // TODO(alexmarkov): revise and uncomment the following assertions
-    // ASSERT(!has_shift_count_check());
-    // ASSERT(shift >= 0);
+    ASSERT(shift >= 0);
     switch (op_kind()) {
       case Token::kSHR: {
         if (shift < 32) {
@@ -6610,7 +6608,7 @@ void ShiftMintOpInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
     __ SmiUntag(shift);
 
     // Deopt if shift is larger than 63 or less than 0.
-    if (has_shift_count_check()) {
+    if (!IsShiftCountInRange()) {
       __ CompareImmediate(shift, kMintShiftCountLimit);
       __ b(deopt, HI);
     }