Support conversion of clamped double values for pixel arrays in Crankshaft.

src/x64/lithium-x64.h

Index: src/x64/lithium-x64.h
diff --git a/src/x64/lithium-x64.h b/src/x64/lithium-x64.h
index 4aa235f13789cfc841b66cf6ead69de961f80e13..0a16b65cb856df1e6503afd58516888e532ba779 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -73,6 +73,9 @@ class LCodeGen;
   V(CheckNonSmi)                                \
   V(CheckPrototypeMaps)                         \
   V(CheckSmi)                                   \
+  V(ClampDoubleToUint8)                         \
+  V(ClampIToUint8)                              \
+  V(ClampTaggedToUint8)                         \
   V(ClassOfTest)                                \
   V(ClassOfTestAndBranch)                       \
   V(CmpID)                                      \
@@ -1907,6 +1910,47 @@ class LCheckSmi: public LTemplateInstruction<0, 1, 0> {
 };
 
 
+class LClampDoubleToUint8: public LTemplateInstruction<1, 1, 1> {
+ public:
+  explicit LClampDoubleToUint8(LOperand* value, LOperand* temp) {
+    inputs_[0] = value;
+    temps_[0] = temp;
+  }
+
+  LOperand* unclamped() { return inputs_[0]; }
+
+  DECLARE_CONCRETE_INSTRUCTION(ClampDoubleToUint8, "clamp-d-to-uint8")
+};
+
+
+class LClampIToUint8: public LTemplateInstruction<1, 1, 0> {
+ public:
+  explicit LClampIToUint8(LOperand* value) {
+    inputs_[0] = value;
+  }
+
+  LOperand* unclamped() { return inputs_[0]; }
+
+  DECLARE_CONCRETE_INSTRUCTION(ClampIToUint8, "clamp-i-to-uint8")
+};
+
+
+class LClampTaggedToUint8: public LTemplateInstruction<1, 1, 2> {
+ public:
+  explicit LClampTaggedToUint8(LOperand* value,
+                               LOperand* temp,
+                               LOperand* temp2) {
+    inputs_[0] = value;
+    temps_[0] = temp;
+    temps_[1] = temp2;
+  }
+
+  LOperand* unclamped() { return inputs_[0]; }
+
+  DECLARE_CONCRETE_INSTRUCTION(ClampTaggedToUint8, "clamp-t-to-uint8")
+};
+
+
 class LCheckNonSmi: public LTemplateInstruction<0, 1, 0> {
  public:
   explicit LCheckNonSmi(LOperand* value) {