S390:[crankshaft] Sign-ext key before array access

src/s390/macro-assembler-s390.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_S390_MACRO_ASSEMBLER_S390_H_
 #define V8_S390_MACRO_ASSEMBLER_S390_H_
 
 #include "src/assembler.h"
 #include "src/bailout-reason.h"
 #include "src/frames.h"
@@ skipping 1570 matching lines @@
     } else if (!dst.is(src)) {
       LoadRR(dst, src);
     }
   }
 
   void IndexToArrayOffset(Register dst, Register src, int elementSizeLog2,
                           bool isSmi) {
     if (isSmi) {
       SmiToArrayOffset(dst, src, elementSizeLog2);
     } else {
+#if V8_TARGET_ARCH_S390X
+      // src (key) is a 32-bit integer.  Sign extension ensures
+      // upper 32-bit does not contain garbage before being used to
+      // reference memory.
+      lgfr(src, src);
+#endif
       ShiftLeftP(dst, src, Operand(elementSizeLog2));
     }
   }
 
   // Untag the source value into destination and jump if source is a smi.
   // Souce and destination can be the same register.
   void UntagAndJumpIfSmi(Register dst, Register src, Label* smi_case);
 
   // Untag the source value into destination and jump if source is not a smi.
   // Souce and destination can be the same register.
@@ skipping 283 matching lines @@
 #define ACCESS_MASM(masm)    \
   masm->stop(__FILE_LINE__); \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_S390_MACRO_ASSEMBLER_S390_H_