[turbofan] Add backend support for signed loads.

src/compiler/x64/instruction-codes-x64.h

Index: src/compiler/x64/instruction-codes-x64.h
diff --git a/src/compiler/x64/instruction-codes-x64.h b/src/compiler/x64/instruction-codes-x64.h
index 1345ce7aa48ead9a04c2a4028d20f30440ab061d..b0a159557de6112ad404cc8d164b0dfac9bb30d0 100644
--- a/src/compiler/x64/instruction-codes-x64.h
+++ b/src/compiler/x64/instruction-codes-x64.h
@@ -46,8 +46,6 @@ namespace compiler {
   V(X64Ror32)                      \
   V(X64Push)                       \
   V(X64PushI)                      \
-  V(X64Movsxlq)                    \
-  V(X64Movl)                       \
   V(X64CallCodeObject)             \
   V(X64CallAddress)                \
   V(PopStack)                      \
@@ -62,20 +60,16 @@ namespace compiler {
   V(SSEFloat64ToUint32)            \
   V(SSEInt32ToFloat64)             \
   V(SSEUint32ToFloat64)            \
-  V(SSELoad)                       \
-  V(SSEStore)                      \
-  V(X64LoadWord8)                  \
-  V(X64StoreWord8)                 \
-  V(X64StoreWord8I)                \
-  V(X64LoadWord16)                 \
-  V(X64StoreWord16)                \
-  V(X64StoreWord16I)               \
-  V(X64LoadWord32)                 \
-  V(X64StoreWord32)                \
-  V(X64StoreWord32I)               \
-  V(X64LoadWord64)                 \
-  V(X64StoreWord64)                \
-  V(X64StoreWord64I)               \
+  V(X64Movsd)                      \
+  V(X64Movsxbl)                    \
+  V(X64Movzxbl)                    \
+  V(X64Movb)                       \
+  V(X64Movsxwl)                    \
+  V(X64Movzxwl)                    \
+  V(X64Movw)                       \
+  V(X64Movl)                       \
+  V(X64Movsxlq)                    \
+  V(X64Movq)                       \
   V(X64StoreWriteBarrier)