MIPS64: Implement optimization utilizing signaling NaN for holes in double arrays.

src/mips64/macro-assembler-mips64.cc

Index: src/mips64/macro-assembler-mips64.cc
diff --git a/src/mips64/macro-assembler-mips64.cc b/src/mips64/macro-assembler-mips64.cc
index 4a2261b868ea5364e91c0101c890ed2ca7bd588b..64b3d552e3167def47cb2772a4e1cf03041bd8e7 100644
--- a/src/mips64/macro-assembler-mips64.cc
+++ b/src/mips64/macro-assembler-mips64.cc
@@ -3865,69 +3865,41 @@ void MacroAssembler::StoreNumberToDoubleElements(Register value_reg,
                                                  Register elements_reg,
                                                  Register scratch1,
                                                  Register scratch2,
-                                                 Register scratch3,
                                                  Label* fail,
                                                  int elements_offset) {
-  Label smi_value, maybe_nan, have_double_value, is_nan, done;
-  Register mantissa_reg = scratch2;
-  Register exponent_reg = scratch3;
+  Label smi_value, done;
 
   // Handle smi values specially.
   JumpIfSmi(value_reg, &smi_value);
 
-  // Ensure that the object is a heap number
+  // Ensure that the object is a heap number.
   CheckMap(value_reg,
            scratch1,
            Heap::kHeapNumberMapRootIndex,
            fail,
            DONT_DO_SMI_CHECK);
 
-  // Check for nan: all NaN values have a value greater (signed) than 0x7ff00000
-  // in the exponent.
-  li(scratch1, Operand(kHoleNanUpper32 & HeapNumber::kExponentMask));
-  lw(exponent_reg, FieldMemOperand(value_reg, HeapNumber::kExponentOffset));
-  Branch(&maybe_nan, ge, exponent_reg, Operand(scratch1));
-
-  lwu(mantissa_reg, FieldMemOperand(value_reg, HeapNumber::kMantissaOffset));
-
-  bind(&have_double_value);
-  // dsll(scratch1, key_reg, kDoubleSizeLog2 - kSmiTagSize);
-  dsra(scratch1, key_reg, 32 - kDoubleSizeLog2);
-  Daddu(scratch1, scratch1, elements_reg);
-  sw(mantissa_reg, FieldMemOperand(
-     scratch1, FixedDoubleArray::kHeaderSize - elements_offset));
-  uint32_t offset = FixedDoubleArray::kHeaderSize - elements_offset +
-      sizeof(kHoleNanLower32);
-  sw(exponent_reg, FieldMemOperand(scratch1, offset));
-  jmp(&done);
-
-  bind(&maybe_nan);
-  // Could be NaN, Infinity or -Infinity. If fraction is not zero, it's NaN,
-  // otherwise it's Infinity or -Infinity, and the non-NaN code path applies.
-  lw(mantissa_reg, FieldMemOperand(value_reg, HeapNumber::kMantissaOffset));
-  Branch(&have_double_value, eq, mantissa_reg, Operand(zero_reg));
-  bind(&is_nan);
-  // Load canonical NaN for storing into the double array.
-  LoadRoot(at, Heap::kNanValueRootIndex);
-  lw(mantissa_reg, FieldMemOperand(at, HeapNumber::kMantissaOffset));
-  lw(exponent_reg, FieldMemOperand(at, HeapNumber::kExponentOffset));
-  jmp(&have_double_value);
+  // Double value, turn potential sNaN into qNan.
+  DoubleRegister double_result = f0;
+  DoubleRegister double_scratch = f2;
+
+  ldc1(double_result, FieldMemOperand(value_reg, HeapNumber::kValueOffset));
+  FPUCanonicalizeNaN(double_result, double_result);
+  Branch(&done);
 
   bind(&smi_value);
+  // scratch1 is now effective address of the double element.
+  // Untag and transfer.
+  mthc1(value_reg, double_scratch);
+  cvt_d_w(double_result, double_scratch);
+
+  bind(&done);
   Daddu(scratch1, elements_reg,
       Operand(FixedDoubleArray::kHeaderSize - kHeapObjectTag -
               elements_offset));
-  // dsll(scratch2, key_reg, kDoubleSizeLog2 - kSmiTagSize);
   dsra(scratch2, key_reg, 32 - kDoubleSizeLog2);
   Daddu(scratch1, scratch1, scratch2);
-  // scratch1 is now effective address of the double element
-
-  Register untagged_value = elements_reg;
-  SmiUntag(untagged_value, value_reg);
-  mtc1(untagged_value, f2);
-  cvt_d_w(f0, f2);
-  sdc1(f0, MemOperand(scratch1, 0));
-  bind(&done);
+  sdc1(double_result, MemOperand(scratch1, 0));
 }
 
 
@@ -3999,6 +3971,10 @@ void MacroAssembler::GetWeakValue(Register value, Handle<WeakCell> cell) {
   ld(value, FieldMemOperand(value, WeakCell::kValueOffset));
 }
 
+void MacroAssembler::FPUCanonicalizeNaN(const DoubleRegister dst,
+                                        const DoubleRegister src) {
+  sub_d(dst, src, kDoubleRegZero);
+}
 
 void MacroAssembler::LoadWeakValue(Register value, Handle<WeakCell> cell,
                                    Label* miss) {