[turbofan] Distinguish between change- and truncate-tagged-to-float64.

src/compiler/simplified-operator-reducer.cc

Index: src/compiler/simplified-operator-reducer.cc
diff --git a/src/compiler/simplified-operator-reducer.cc b/src/compiler/simplified-operator-reducer.cc
index 6fbf16ed791925f0e4bcd8a82de31308c6d880b6..f27741c2ca31d6bd4edb4134d2148eedc6ba7031 100644
--- a/src/compiler/simplified-operator-reducer.cc
+++ b/src/compiler/simplified-operator-reducer.cc
@@ -60,7 +60,8 @@ Reduction SimplifiedOperatorReducer::Reduce(Node* node) {
       }
       break;
     }
-    case IrOpcode::kChangeTaggedToFloat64: {
+    case IrOpcode::kChangeTaggedToFloat64:
+    case IrOpcode::kTruncateTaggedToFloat64: {
       NumberMatcher m(node->InputAt(0));
       if (m.HasValue()) return ReplaceFloat64(m.Value());
       if (m.IsChangeFloat64ToTagged()) return Replace(m.node()->InputAt(0));