MIPS: Fix register confusion in non-VFP3 BinaryOpStubs on ARM

src/mips/code-stubs-mips.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 716 matching lines @@
                                  scratch3);
 
   __ bind(&done);
 }
 
 
 void FloatingPointHelper::ConvertIntToDouble(MacroAssembler* masm,
                                              Register int_scratch,
                                              Destination destination,
                                              FPURegister double_dst,
-                                             Register dst1,
-                                             Register dst2,
+                                             Register dst_mantissa,
+                                             Register dst_exponent,
                                              Register scratch2,
                                              FPURegister single_scratch) {
   ASSERT(!int_scratch.is(scratch2));
-  ASSERT(!int_scratch.is(dst1));
-  ASSERT(!int_scratch.is(dst2));
+  ASSERT(!int_scratch.is(dst_mantissa));
+  ASSERT(!int_scratch.is(dst_exponent));
 
   Label done;
 
   if (CpuFeatures::IsSupported(FPU)) {
     CpuFeatures::Scope scope(FPU);
     __ mtc1(int_scratch, single_scratch);
     __ cvt_d_w(double_dst, single_scratch);
     if (destination == kCoreRegisters) {
-      __ Move(dst1, dst2, double_dst);
+      __ Move(dst_mantissa, dst_exponent, double_dst);
     }
   } else {
     Label fewer_than_20_useful_bits;
     // Expected output:
-    // |         dst2            |         dst1            |
+    // |       dst_exponent      |       dst_mantissa      |
     // | s |   exp   |              mantissa               |
 
     // Check for zero.
-    __ mov(dst2, int_scratch);
-    __ mov(dst1, int_scratch);
+    __ mov(dst_exponent, int_scratch);
+    __ mov(dst_mantissa, int_scratch);
     __ Branch(&done, eq, int_scratch, Operand(zero_reg));
 
     // Preload the sign of the value.
-    __ And(dst2, int_scratch, Operand(HeapNumber::kSignMask));
+    __ And(dst_exponent, int_scratch, Operand(HeapNumber::kSignMask));
     // Get the absolute value of the object (as an unsigned integer).
     Label skip_sub;
-    __ Branch(&skip_sub, ge, dst2, Operand(zero_reg));
+    __ Branch(&skip_sub, ge, dst_exponent, Operand(zero_reg));
     __ Subu(int_scratch, zero_reg, int_scratch);
     __ bind(&skip_sub);
 
     // Get mantissa[51:20].
 
     // Get the position of the first set bit.
-    __ Clz(dst1, int_scratch);
+    __ Clz(dst_mantissa, int_scratch);
     __ li(scratch2, 31);
-    __ Subu(dst1, scratch2, dst1);
+    __ Subu(dst_mantissa, scratch2, dst_mantissa);
 
     // Set the exponent.
-    __ Addu(scratch2, dst1, Operand(HeapNumber::kExponentBias));
-    __ Ins(dst2, scratch2,
+    __ Addu(scratch2, dst_mantissa, Operand(HeapNumber::kExponentBias));
+    __ Ins(dst_exponent, scratch2,
         HeapNumber::kExponentShift, HeapNumber::kExponentBits);
 
     // Clear the first non null bit.
     __ li(scratch2, Operand(1));
-    __ sllv(scratch2, scratch2, dst1);
+    __ sllv(scratch2, scratch2, dst_mantissa);
     __ li(at, -1);
     __ Xor(scratch2, scratch2, at);
     __ And(int_scratch, int_scratch, scratch2);
 
     // Get the number of bits to set in the lower part of the mantissa.
-    __ Subu(scratch2, dst1, Operand(HeapNumber::kMantissaBitsInTopWord));
+    __ Subu(scratch2, dst_mantissa,
+        Operand(HeapNumber::kMantissaBitsInTopWord));
     __ Branch(&fewer_than_20_useful_bits, lt, scratch2, Operand(zero_reg));
     // Set the higher 20 bits of the mantissa.
     __ srlv(at, int_scratch, scratch2);
-    __ or_(dst2, dst2, at);
+    __ or_(dst_exponent, dst_exponent, at);
     __ li(at, 32);
     __ subu(scratch2, at, scratch2);
-    __ sllv(dst1, int_scratch, scratch2);
+    __ sllv(dst_mantissa, int_scratch, scratch2);
     __ Branch(&done);
 
     __ bind(&fewer_than_20_useful_bits);
     __ li(at, HeapNumber::kMantissaBitsInTopWord);
-    __ subu(scratch2, at, dst1);
+    __ subu(scratch2, at, dst_mantissa);
     __ sllv(scratch2, int_scratch, scratch2);
-    __ Or(dst2, dst2, scratch2);
-    // Set dst1 to 0.
-    __ mov(dst1, zero_reg);
+    __ Or(dst_exponent, dst_exponent, scratch2);
+    // Set dst_mantissa to 0.
+    __ mov(dst_mantissa, zero_reg);
   }
   __ bind(&done);
 }
 
 
 void FloatingPointHelper::LoadNumberAsInt32Double(MacroAssembler* masm,
                                                   Register object,
                                                   Destination destination,
                                                   DoubleRegister double_dst,
                                                   DoubleRegister double_scratch,
-                                                  Register dst1,
-                                                  Register dst2,
+                                                  Register dst_mantissa,
+                                                  Register dst_exponent,
                                                   Register heap_number_map,
                                                   Register scratch1,
                                                   Register scratch2,
                                                   FPURegister single_scratch,
                                                   Label* not_int32) {
   ASSERT(!scratch1.is(object) && !scratch2.is(object));
   ASSERT(!scratch1.is(scratch2));
   ASSERT(!heap_number_map.is(object) &&
          !heap_number_map.is(scratch1) &&
          !heap_number_map.is(scratch2));
 
   Label done, obj_is_not_smi;
 
   __ JumpIfNotSmi(object, &obj_is_not_smi);
   __ SmiUntag(scratch1, object);
-  ConvertIntToDouble(masm, scratch1, destination, double_dst, dst1, dst2,
-                     scratch2, single_scratch);
+  ConvertIntToDouble(masm, scratch1, destination, double_dst, dst_mantissa,
+                     dst_exponent, scratch2, single_scratch);
   __ Branch(&done);
 
   __ bind(&obj_is_not_smi);
   __ AssertRootValue(heap_number_map,
                      Heap::kHeapNumberMapRootIndex,
                      "HeapNumberMap register clobbered.");
   __ JumpIfNotHeapNumber(object, heap_number_map, scratch1, not_int32);
 
   // Load the number.
   if (CpuFeatures::IsSupported(FPU)) {
     CpuFeatures::Scope scope(FPU);
     // Load the double value.
     __ ldc1(double_dst, FieldMemOperand(object, HeapNumber::kValueOffset));
 
     Register except_flag = scratch2;
     __ EmitFPUTruncate(kRoundToZero,
                        scratch1,
                        double_dst,
                        at,
                        double_scratch,
                        except_flag,
                        kCheckForInexactConversion);
 
     // Jump to not_int32 if the operation did not succeed.
     __ Branch(not_int32, ne, except_flag, Operand(zero_reg));
 
     if (destination == kCoreRegisters) {
-      __ Move(dst1, dst2, double_dst);
+      __ Move(dst_mantissa, dst_exponent, double_dst);
     }
 
   } else {
     ASSERT(!scratch1.is(object) && !scratch2.is(object));
     // Load the double value in the destination registers.
-    __ lw(dst2, FieldMemOperand(object, HeapNumber::kExponentOffset));
-    __ lw(dst1, FieldMemOperand(object, HeapNumber::kMantissaOffset));
+    bool save_registers = object.is(dst_mantissa) || object.is(dst_exponent);
+    if (save_registers) {
+      // Save both output registers, because the other one probably holds
+      // an important value too.
+      __ Push(dst_exponent, dst_mantissa);
+    }
+    __ lw(dst_exponent, FieldMemOperand(object, HeapNumber::kExponentOffset));
+    __ lw(dst_mantissa, FieldMemOperand(object, HeapNumber::kMantissaOffset));
 
     // Check for 0 and -0.
-    __ And(scratch1, dst1, Operand(~HeapNumber::kSignMask));
-    __ Or(scratch1, scratch1, Operand(dst2));
-    __ Branch(&done, eq, scratch1, Operand(zero_reg));
+    Label zero;
+    __ And(scratch1, dst_exponent, Operand(~HeapNumber::kSignMask));
+    __ Or(scratch1, scratch1, Operand(dst_mantissa));
+    __ Branch(&zero, eq, scratch1, Operand(zero_reg));
 
     // Check that the value can be exactly represented by a 32-bit integer.
     // Jump to not_int32 if that's not the case.
-    DoubleIs32BitInteger(masm, dst1, dst2, scratch1, scratch2, not_int32);
+    Label restore_input_and_miss;
+    DoubleIs32BitInteger(masm, dst_exponent, dst_mantissa, scratch1, scratch2,
+                         &restore_input_and_miss);
 
-    // dst1 and dst2 were trashed. Reload the double value.
-    __ lw(dst2, FieldMemOperand(object, HeapNumber::kExponentOffset));
-    __ lw(dst1, FieldMemOperand(object, HeapNumber::kMantissaOffset));
+    // dst_* were trashed. Reload the double value.
+    if (save_registers) {
+      __ Pop(dst_exponent, dst_mantissa);
+    }
+    __ lw(dst_exponent, FieldMemOperand(object, HeapNumber::kExponentOffset));
+    __ lw(dst_mantissa, FieldMemOperand(object, HeapNumber::kMantissaOffset));
+    __ Branch(&done);
+
+    __ bind(&restore_input_and_miss);
+    if (save_registers) {
+      __ Pop(dst_exponent, dst_mantissa);
+    }
+    __ Branch(not_int32);
+
+    __ bind(&zero);
+    if (save_registers) {
+      __ Drop(2);
+    }
   }
 
   __ bind(&done);
 }
 
 
 void FloatingPointHelper::LoadNumberAsInt32(MacroAssembler* masm,
                                             Register object,
                                             Register dst,
                                             Register heap_number_map,
@@ skipping 75 matching lines @@
   __ Branch(not_int32, ne, object, Operand(at));
   // |undefined| is truncated to 0.
   __ li(dst, Operand(Smi::FromInt(0)));
   // Fall through.
 
   __ bind(&done);
 }
 
 
 void FloatingPointHelper::DoubleIs32BitInteger(MacroAssembler* masm,
-                                               Register src1,
-                                               Register src2,
+                                               Register src_exponent,
+                                               Register src_mantissa,
                                                Register dst,
                                                Register scratch,
                                                Label* not_int32) {
   // Get exponent alone in scratch.
   __ Ext(scratch,
-         src1,
+         src_exponent,
          HeapNumber::kExponentShift,
          HeapNumber::kExponentBits);
 
   // Substract the bias from the exponent.
   __ Subu(scratch, scratch, Operand(HeapNumber::kExponentBias));
 
   // src1: higher (exponent) part of the double value.
   // src2: lower (mantissa) part of the double value.
   // scratch: unbiased exponent.
 
   // Fast cases. Check for obvious non 32-bit integer values.
   // Negative exponent cannot yield 32-bit integers.
   __ Branch(not_int32, lt, scratch, Operand(zero_reg));
   // Exponent greater than 31 cannot yield 32-bit integers.
   // Also, a positive value with an exponent equal to 31 is outside of the
   // signed 32-bit integer range.
   // Another way to put it is that if (exponent - signbit) > 30 then the
   // number cannot be represented as an int32.
   Register tmp = dst;
-  __ srl(at, src1, 31);
+  __ srl(at, src_exponent, 31);
   __ subu(tmp, scratch, at);
   __ Branch(not_int32, gt, tmp, Operand(30));
   // - Bits [21:0] in the mantissa are not null.
-  __ And(tmp, src2, 0x3fffff);
+  __ And(tmp, src_mantissa, 0x3fffff);
   __ Branch(not_int32, ne, tmp, Operand(zero_reg));
 
   // Otherwise the exponent needs to be big enough to shift left all the
   // non zero bits left. So we need the (30 - exponent) last bits of the
   // 31 higher bits of the mantissa to be null.
   // Because bits [21:0] are null, we can check instead that the
   // (32 - exponent) last bits of the 32 higher bits of the mantissa are null.
 
   // Get the 32 higher bits of the mantissa in dst.
   __ Ext(dst,
-         src2,
+         src_mantissa,
          HeapNumber::kMantissaBitsInTopWord,
          32 - HeapNumber::kMantissaBitsInTopWord);
-  __ sll(at, src1, HeapNumber::kNonMantissaBitsInTopWord);
+  __ sll(at, src_exponent, HeapNumber::kNonMantissaBitsInTopWord);
   __ or_(dst, dst, at);
 
   // Create the mask and test the lower bits (of the higher bits).
   __ li(at, 32);
   __ subu(scratch, at, scratch);
-  __ li(src2, 1);
-  __ sllv(src1, src2, scratch);
-  __ Subu(src1, src1, Operand(1));
-  __ And(src1, dst, src1);
-  __ Branch(not_int32, ne, src1, Operand(zero_reg));
+  __ li(src_mantissa, 1);
+  __ sllv(src_exponent, src_mantissa, scratch);
+  __ Subu(src_exponent, src_exponent, Operand(1));
+  __ And(src_exponent, dst, src_exponent);
+  __ Branch(not_int32, ne, src_exponent, Operand(zero_reg));
 }
 
 
 void FloatingPointHelper::CallCCodeForDoubleOperation(
     MacroAssembler* masm,
     Token::Value op,
     Register heap_number_result,
     Register scratch) {
   // Using core registers:
   // a0: Left value (least significant part of mantissa).
@@ skipping 6740 matching lines @@
   __ Pop(ra, t1, a1);
   __ Ret();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS