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

src/crankshaft/s390/lithium-codegen-s390.cc

Index: src/crankshaft/s390/lithium-codegen-s390.cc
diff --git a/src/crankshaft/s390/lithium-codegen-s390.cc b/src/crankshaft/s390/lithium-codegen-s390.cc
index 32784a167f180dc1f6b74ad4f370cb70b0dbaf0a..e0b8ec72c16da595f5936c3edd782d85233ba91a 100644
--- a/src/crankshaft/s390/lithium-codegen-s390.cc
+++ b/src/crankshaft/s390/lithium-codegen-s390.cc
@@ -1278,7 +1278,7 @@ void LCodeGen::DoFlooringDivI(LFlooringDivI* instr) {
   __ beq(&done, Label::kNear);
 
   // We performed a truncating division. Correct the result.
-  __ SubP(result, result, Operand(1));
+  __ Sub32(result, result, Operand(1));
   __ bind(&done);
 }
 
@@ -4226,7 +4226,22 @@ void LCodeGen::DoStoreKeyedFixedArray(LStoreKeyed* instr) {
     if (hinstr->key()->representation().IsSmi()) {
       __ SmiToPtrArrayOffset(scratch, key);
     } else {
-      __ ShiftLeftP(scratch, key, Operand(kPointerSizeLog2));
+      if (instr->hydrogen()->IsDehoisted()) {
+#if V8_TARGET_ARCH_S390X
+        // If array access is dehoisted, the key, being an int32, can contain
+        // a negative value, as needs to be sign-extended to 64-bit for
+        // memory access.
+        __ lgfr(key, key);
+#endif
+        __ ShiftLeftP(scratch, key, Operand(kPointerSizeLog2));
+      } else {
+        // Small optimization to reduce pathlength.  After Bounds Check,
+        // the key is guaranteed to be non-negative.  Leverage RISBG,
+        // which also performs zero-extension.
+        __ risbg(scratch, key, Operand(32 - kPointerSizeLog2),
+                 Operand(63 - kPointerSizeLog2), Operand(kPointerSizeLog2),
+                 true);
+      }
     }
   }