Optionally use 31-bits SMI value for 64-bit system

src/x64/stub-cache-x64.cc

Index: src/x64/stub-cache-x64.cc
diff --git a/src/x64/stub-cache-x64.cc b/src/x64/stub-cache-x64.cc
index 7ad250a4ad86412d226dd2cec9ee961306e0184c..0078cc32aee3d92b5c544875d077c99603b3eadf 100644
--- a/src/x64/stub-cache-x64.cc
+++ b/src/x64/stub-cache-x64.cc
@@ -2246,26 +2246,28 @@ Handle<Code> CallStubCompiler::CompileMathAbsCall(
   Label not_smi;
   STATIC_ASSERT(kSmiTag == 0);
   __ JumpIfNotSmi(rax, &not_smi);
-  __ SmiToInteger32(rax, rax);
 
   // Set ebx to 1...1 (== -1) if the argument is negative, or to 0...0
   // otherwise.
-  __ movl(rbx, rax);
-  __ sarl(rbx, Immediate(kBitsPerInt - 1));
+  __ movq(rbx, rax);
+  __ sar(rbx, Immediate(kBitsPerPointer - 1));
 
   // Do bitwise not or do nothing depending on ebx.
-  __ xorl(rax, rbx);
+  __ xor_(rax, rbx);
 
   // Add 1 or do nothing depending on ebx.
-  __ subl(rax, rbx);
+  if (SmiValuesAre32Bits()) {
+    __ subq(rax, rbx);
+  } else {
+    ASSERT(SmiValuesAre31Bits());
+    __ subl(rax, rbx);
+  }
 
   // If the result is still negative, go to the slow case.
   // This only happens for the most negative smi.
   Label slow;
   __ j(negative, &slow);
 
-  // Smi case done.
-  __ Integer32ToSmi(rax, rax);
   __ ret(2 * kPointerSize);
 
   // Check if the argument is a heap number and load its value.
@@ -3058,6 +3060,7 @@ static void GenerateSmiKeyCheck(MacroAssembler* masm,
   __ ucomisd(xmm_scratch1, xmm_scratch0);
   __ j(not_equal, fail);
   __ j(parity_even, fail);  // NaN.
+  __ JumpIfNotValidSmiValue(scratch, fail);
   __ Integer32ToSmi(key, scratch);
   __ bind(&key_ok);
 }