Prevent deopt when assigning double values to typed arrays

src/ia32/macro-assembler-ia32.h

Index: src/ia32/macro-assembler-ia32.h
diff --git a/src/ia32/macro-assembler-ia32.h b/src/ia32/macro-assembler-ia32.h
index f1666ba411fc88c51bcf2956b1dba4cdbf20126f..2cfee3afe21e910f8acdee4aaebaa0c4892f3647 100644
--- a/src/ia32/macro-assembler-ia32.h
+++ b/src/ia32/macro-assembler-ia32.h
@@ -237,6 +237,42 @@ class MacroAssembler: public Assembler {
   // jcc instructions (je, ja, jae, jb, jbe, je, and jz).
   void FCmp();
 
+  void ClampUInt8(Register reg) {
+    NearLabel done;
+    test(reg, Immediate(0xFFFFFF00));
+    j(zero, &done);
+    setcc(negative, reg);  // 1 if negative, 0 if positive.
+    dec_b(reg);  // 0 if negative, 255 if positive.
+    bind(&done);
+  }
+
+  void ClampDoubleToUInt8(XMMRegister input_reg, Register result_reg) {
+    NearLabel above_zero;
+    NearLabel done;
+    NearLabel in_bounds;
+    ExternalReference zero = ExternalReference::address_of_zero();
+    movdbl(xmm0, Operand::StaticVariable(zero));
+    ucomisd(input_reg, xmm0);
+    j(above, &above_zero);
+    Set(result_reg, Immediate(0));
+    jmp(&done);
+    bind(&above_zero);
+    ExternalReference uint8_max_value =
+        ExternalReference::address_of_uint8_max_value();
+    movdbl(xmm0, Operand::StaticVariable(uint8_max_value));
+    ucomisd(input_reg, xmm0);
+    j(below_equal, &in_bounds);
+    Set(result_reg, Immediate(255));
+    jmp(&done);
+    bind(&in_bounds);
+    ExternalReference one_half =
+        ExternalReference::address_of_one_half();
+    movdbl(xmm0, Operand::StaticVariable(one_half));
+    addsd(input_reg, xmm0);
+    cvttsd2si(result_reg, Operand(input_reg));
+    bind(&done);
+  }
+
   // Smi tagging support.
   void SmiTag(Register reg) {
     ASSERT(kSmiTag == 0);