Fixed corner cases in truncation behavior when storing to TypedArrays.

src/x64/stub-cache-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 3383 matching lines @@
     if (elements_kind == EXTERNAL_FLOAT_ELEMENTS) {
       __ cvtsd2ss(xmm0, xmm0);
       __ movss(Operand(rbx, rdi, times_4, 0), xmm0);
       __ ret(0);
     } else if (elements_kind == EXTERNAL_DOUBLE_ELEMENTS) {
       __ movsd(Operand(rbx, rdi, times_8, 0), xmm0);
       __ ret(0);
     } else {
       // Perform float-to-int conversion with truncation (round-to-zero)
       // behavior.
+      // Fast path: use machine instruction to convert to int64. If that
+      // fails (out-of-range), go into the runtime.
+      __ cvttsd2siq(rdx, xmm0);
+      __ Set(kScratchRegister, V8_UINT64_C(0x8000000000000000));
+      __ cmpq(rdx, kScratchRegister);
+      __ j(equal, &slow);
 
-      // Convert to int32 and store the low byte/word.
-      // If the value is NaN or +/-infinity, the result is 0x80000000,
-      // which is automatically zero when taken mod 2^n, n < 32.
       // rdx: value (converted to an untagged integer)
       // rdi: untagged index
       // rbx: base pointer of external storage
       switch (elements_kind) {
         case EXTERNAL_BYTE_ELEMENTS:
         case EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
-          __ cvttsd2si(rdx, xmm0);
           __ movb(Operand(rbx, rdi, times_1, 0), rdx);
           break;
         case EXTERNAL_SHORT_ELEMENTS:
         case EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
-          __ cvttsd2si(rdx, xmm0);
           __ movw(Operand(rbx, rdi, times_2, 0), rdx);
           break;
         case EXTERNAL_INT_ELEMENTS:
         case EXTERNAL_UNSIGNED_INT_ELEMENTS:
-          // Convert to int64, so that NaN and infinities become
-          // 0x8000000000000000, which is zero mod 2^32.
-          __ cvttsd2siq(rdx, xmm0);
           __ movl(Operand(rbx, rdi, times_4, 0), rdx);
           break;
         case EXTERNAL_PIXEL_ELEMENTS:
         case EXTERNAL_FLOAT_ELEMENTS:
         case EXTERNAL_DOUBLE_ELEMENTS:
         case FAST_ELEMENTS:
         case FAST_SMI_ONLY_ELEMENTS:
         case FAST_DOUBLE_ELEMENTS:
         case DICTIONARY_ELEMENTS:
         case NON_STRICT_ARGUMENTS_ELEMENTS:
@@ skipping 388 matching lines @@
     __ jmp(ic_slow, RelocInfo::CODE_TARGET);
   }
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64