Optionally use 31-bits SMI value for 64-bit system

src/x64/debug-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 108 matching lines @@
     ASSERT((object_regs & non_object_regs) == 0);
     for (int i = 0; i < kNumJSCallerSaved; i++) {
       int r = JSCallerSavedCode(i);
       Register reg = { r };
       ASSERT(!reg.is(kScratchRegister));
       if ((object_regs & (1 << r)) != 0) {
         __ push(reg);
       }
       // Store the 64-bit value as two smis.
       if ((non_object_regs & (1 << r)) != 0) {
         __ movq(kScratchRegister, reg);

[danno, 2013/08/01 16:45:41]

Watch out. You have change the semantic here slightly, since 64-bits can be
encoded in two 31-bit values.  However, in practice, all the uses of this code
actually only expect integers (32 bits) to be encoded, so I this you can change
the semantic to only pack the 32 lower bits sign extended.

I think this code sequence (and the restore sequence in this file) should be
moved into the macro assembler:

__ PushInt32AsTwoSmis(reg, kScratchRegister)
__ PopInt32AsTwoSmis(reg, kScratchRegister);

and then hide the smi size check in the macro assembler.

[haitao.feng, 2013/08/02 09:35:51]

Done. I used the name PushInt64AsTwoSmis and PopInt64AsTwoSmis.

-        __ Integer32ToSmi(reg, reg);
-        __ push(reg);
-        __ sar(kScratchRegister, Immediate(32));
-        __ Integer32ToSmi(kScratchRegister, kScratchRegister);
-        __ push(kScratchRegister);
+        if (kSmiValueSize == 32) {
+          __ Integer32ToSmi(reg, reg);
+          __ push(reg);
+          __ sar(kScratchRegister, Immediate(32));
+          __ Integer32ToSmi(kScratchRegister, kScratchRegister);
+          __ push(kScratchRegister);
+        } else {
+          ASSERT(kSmiValueSize == 31);
+          __ shr(reg, Immediate(63));
+          __ shll(reg, Immediate(1));
+          __ push(reg);
+          __ shl(kScratchRegister, Immediate(1));
+          __ push(kScratchRegister);
+        }
       }
     }
 
 #ifdef DEBUG
     __ RecordComment("// Calling from debug break to runtime - come in - over");
 #endif
     __ Set(rax, 0);  // No arguments (argc == 0).
     __ movq(rbx, ExternalReference::debug_break(masm->isolate()));
 
     CEntryStub ceb(1);
     __ CallStub(&ceb);
 
     // Restore the register values from the expression stack.
     for (int i = kNumJSCallerSaved - 1; i >= 0; i--) {
       int r = JSCallerSavedCode(i);
       Register reg = { r };
       if (FLAG_debug_code) {
         __ Set(reg, kDebugZapValue);
       }
       if ((object_regs & (1 << r)) != 0) {
         __ pop(reg);
       }
       // Reconstruct the 64-bit value from two smis.
       if ((non_object_regs & (1 << r)) != 0) {
         __ pop(kScratchRegister);
-        __ SmiToInteger32(kScratchRegister, kScratchRegister);
-        __ shl(kScratchRegister, Immediate(32));
-        __ pop(reg);
-        __ SmiToInteger32(reg, reg);
-        __ or_(reg, kScratchRegister);
+        if (kSmiValueSize == 32) {
+          __ SmiToInteger32(kScratchRegister, kScratchRegister);
+          __ shl(kScratchRegister, Immediate(32));
+          __ pop(reg);
+          __ SmiToInteger32(reg, reg);
+          __ or_(reg, kScratchRegister);
+        } else {
+          ASSERT(kSmiValueSize == 31);
+          __ shr(kScratchRegister, Immediate(1));
+          __ pop(reg);
+          __ shl(reg, Immediate(62));
+          __ or_(reg, kScratchRegister);
+        }
       }
     }
 
     // Read current padding counter and skip corresponding number of words.
     __ pop(kScratchRegister);
     __ SmiToInteger32(kScratchRegister, kScratchRegister);
     __ lea(rsp, Operand(rsp, kScratchRegister, times_pointer_size, 0));
 
     // Get rid of the internal frame.
   }
@@ skipping 179 matching lines @@
 
 const bool Debug::kFrameDropperSupported = true;
 
 #undef __
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64