[turbofan] ARM64: Use zr to store immediate zero

src/compiler/arm64/code-generator-arm64.cc

Index: src/compiler/arm64/code-generator-arm64.cc
diff --git a/src/compiler/arm64/code-generator-arm64.cc b/src/compiler/arm64/code-generator-arm64.cc
index d847ae1b4f08e77e83a48374f0cef12aac3276cc..5424826ba6e6716c9f4d3b1263689196acb7978d 100644
--- a/src/compiler/arm64/code-generator-arm64.cc
+++ b/src/compiler/arm64/code-generator-arm64.cc
@@ -33,6 +33,28 @@ class Arm64OperandConverter final : public InstructionOperandConverter {
     return InputDoubleRegister(index);
   }
 
+  CPURegister InputFloat32OrZeroRegister(size_t index) {
+    if (instr_->InputAt(index)->IsImmediate()) {
+      DCHECK(instr_->InputAt(index)->IsImmediate() &&
+             (InputFloat32(index) == 0.0f) &&
+             (copysignf(1.0f, InputFloat32(index)) > 0.0f));

[Benedikt Meurer, 2016/05/03 17:33:20]

Use std::signbit or bit_cast<int32_t>(InputFloat32(index)) == 0

[martyn.capewell, 2016/05/04 09:47:47]

Done.

+      return wzr;
+    }
+    DCHECK(instr_->InputAt(index)->IsDoubleRegister());
+    return InputDoubleRegister(index).S();
+  }
+
+  CPURegister InputFloat64OrZeroRegister(size_t index) {
+    if (instr_->InputAt(index)->IsImmediate()) {
+      DCHECK(instr_->InputAt(index)->IsImmediate() &&
+             (InputDouble(index) == 0.0f) &&
+             (copysign(1.0, InputDouble(index)) > 0.0));

[Benedikt Meurer, 2016/05/03 17:33:20]

Use std::signbit or bit_cast<int64_t>(InputFloat64(index)) == 0

[martyn.capewell, 2016/05/04 09:47:47]

Done.

+      return xzr;
+    }
+    DCHECK(instr_->InputAt(index)->IsDoubleRegister());
+    return InputDoubleRegister(index);
+  }
+
   size_t OutputCount() { return instr_->OutputCount(); }
 
   DoubleRegister OutputFloat32Register() { return OutputDoubleRegister().S(); }
@@ -416,27 +438,25 @@ Condition FlagsConditionToCondition(FlagsCondition condition) {
     __ Bind(ool->exit());                                    \
   } while (0)
 
-
-#define ASSEMBLE_CHECKED_STORE_FLOAT(width)          \
-  do {                                               \
-    auto buffer = i.InputRegister(0);                \
-    auto offset = i.InputRegister32(1);              \
-    auto length = i.InputOperand32(2);               \
-    auto value = i.InputFloat##width##Register(3);   \
-    __ Cmp(offset, length);                          \
-    Label done;                                      \
-    __ B(hs, &done);                                 \
-    __ Str(value, MemOperand(buffer, offset, UXTW)); \
-    __ Bind(&done);                                  \
+#define ASSEMBLE_CHECKED_STORE_FLOAT(width)              \
+  do {                                                   \
+    auto buffer = i.InputRegister(0);                    \
+    auto offset = i.InputRegister32(1);                  \
+    auto length = i.InputOperand32(2);                   \
+    auto value = i.InputFloat##width##OrZeroRegister(3); \
+    __ Cmp(offset, length);                              \
+    Label done;                                          \
+    __ B(hs, &done);                                     \
+    __ Str(value, MemOperand(buffer, offset, UXTW));     \
+    __ Bind(&done);                                      \
   } while (0)
 
-
 #define ASSEMBLE_CHECKED_STORE_INTEGER(asm_instr)          \
   do {                                                     \
     auto buffer = i.InputRegister(0);                      \
     auto offset = i.InputRegister32(1);                    \
     auto length = i.InputOperand32(2);                     \
-    auto value = i.InputRegister32(3);                     \
+    auto value = i.InputOrZeroRegister32(3);               \
     __ Cmp(offset, length);                                \
     Label done;                                            \
     __ B(hs, &done);                                       \
@@ -444,13 +464,12 @@ Condition FlagsConditionToCondition(FlagsCondition condition) {
     __ Bind(&done);                                        \
   } while (0)
 
-
 #define ASSEMBLE_CHECKED_STORE_INTEGER_64(asm_instr)       \
   do {                                                     \
     auto buffer = i.InputRegister(0);                      \
     auto offset = i.InputRegister32(1);                    \
     auto length = i.InputOperand32(2);                     \
-    auto value = i.InputRegister(3);                       \
+    auto value = i.InputOrZeroRegister64(3);               \
     __ Cmp(offset, length);                                \
     Label done;                                            \
     __ B(hs, &done);                                       \
@@ -458,7 +477,6 @@ Condition FlagsConditionToCondition(FlagsCondition condition) {
     __ Bind(&done);                                        \
   } while (0)
 
-
 #define ASSEMBLE_SHIFT(asm_instr, width)                                    \
   do {                                                                      \
     if (instr->InputAt(1)->IsRegister()) {                                  \
@@ -1337,7 +1355,7 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       __ Ldrsb(i.OutputRegister(), i.MemoryOperand());
       break;
     case kArm64Strb:
-      __ Strb(i.InputRegister(2), i.MemoryOperand());
+      __ Strb(i.InputOrZeroRegister64(2), i.MemoryOperand());
       break;
     case kArm64Ldrh:
       __ Ldrh(i.OutputRegister(), i.MemoryOperand());
@@ -1346,31 +1364,31 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       __ Ldrsh(i.OutputRegister(), i.MemoryOperand());
       break;
     case kArm64Strh:
-      __ Strh(i.InputRegister(2), i.MemoryOperand());
+      __ Strh(i.InputOrZeroRegister64(2), i.MemoryOperand());
       break;
     case kArm64LdrW:
       __ Ldr(i.OutputRegister32(), i.MemoryOperand());
       break;
     case kArm64StrW:
-      __ Str(i.InputRegister32(2), i.MemoryOperand());
+      __ Str(i.InputOrZeroRegister32(2), i.MemoryOperand());
       break;
     case kArm64Ldr:
       __ Ldr(i.OutputRegister(), i.MemoryOperand());
       break;
     case kArm64Str:
-      __ Str(i.InputRegister(2), i.MemoryOperand());
+      __ Str(i.InputOrZeroRegister64(2), i.MemoryOperand());
       break;
     case kArm64LdrS:
       __ Ldr(i.OutputDoubleRegister().S(), i.MemoryOperand());
       break;
     case kArm64StrS:
-      __ Str(i.InputDoubleRegister(2).S(), i.MemoryOperand());
+      __ Str(i.InputFloat32OrZeroRegister(2), i.MemoryOperand());
       break;
     case kArm64LdrD:
       __ Ldr(i.OutputDoubleRegister(), i.MemoryOperand());
       break;
     case kArm64StrD:
-      __ Str(i.InputDoubleRegister(2), i.MemoryOperand());
+      __ Str(i.InputFloat64OrZeroRegister(2), i.MemoryOperand());
       break;
     case kCheckedLoadInt8:
       ASSEMBLE_CHECKED_LOAD_INTEGER(Ldrsb);