[v8-dev] MIPS: Add support to load/store byte fields. (issue 25460003)

[kilvadyb]

Reviewers: danno, Benedikt Meurer, Paul Lind, kisg, palfia,
Description:
MIPS: Add support to load/store byte fields.

Port r17079 (0885ac2)

Original commit message:
This adds a new Byte representation and support for zero-extended
loads in HLoadNamedField and truncated stores in HStoreNamedField.

BUG=

Please review this at https://codereview.chromium.org/25460003/

SVN Base: https://github.com/v8/v8.git@gbl

Affected files (+32, -8 lines):
  M src/mips/lithium-codegen-mips.cc


Index: src/mips/lithium-codegen-mips.cc
diff --git a/src/mips/lithium-codegen-mips.cc  
b/src/mips/lithium-codegen-mips.cc
index  
38b0ff5274d4c44cda241072aa8e7a7ab05a54be..7481c4d99dd781459f7b8d9ade147b74e5a51065  
100644
--- a/src/mips/lithium-codegen-mips.cc
+++ b/src/mips/lithium-codegen-mips.cc
@@ -2952,7 +2952,12 @@ void LCodeGen::DoLoadNamedField(LLoadNamedField*  
instr) {

   if (access.IsExternalMemory()) {
     Register result = ToRegister(instr->result());
-    __ lw(result, MemOperand(object, offset));
+    MemOperand operand = MemOperand(object, offset);
+    if (access.representation().IsByte()) {
+      __ lb(result, operand);
+    } else {
+      __ lw(result, operand);
+    }
     return;
   }

@@ -2963,11 +2968,15 @@ void LCodeGen::DoLoadNamedField(LLoadNamedField*  
instr) {
   }

   Register result = ToRegister(instr->result());
-  if (access.IsInobject()) {
-    __ lw(result, FieldMemOperand(object, offset));
-  } else {
+  if (!access.IsInobject()) {
     __ lw(result, FieldMemOperand(object, JSObject::kPropertiesOffset));
-    __ lw(result, FieldMemOperand(result, offset));
+    object = result;
+  }
+  MemOperand operand = FieldMemOperand(object, offset);
+  if (access.representation().IsByte()) {
+    __ lb(result, operand);
+  } else {
+    __ lw(result, operand);
   }
 }

@@ -4131,7 +4140,12 @@ void LCodeGen::DoStoreNamedField(LStoreNamedField*  
instr) {

   if (access.IsExternalMemory()) {
     Register value = ToRegister(instr->value());
-    __ sw(value, MemOperand(object, offset));
+    MemOperand operand = MemOperand(object, offset);
+    if (representation.IsByte()) {
+      __ sb(value, operand);
+    } else {
+      __ sw(value, operand);
+    }
     return;
   }

@@ -4176,7 +4190,12 @@ void LCodeGen::DoStoreNamedField(LStoreNamedField*  
instr) {
       instr->hydrogen()->value()->IsHeapObject()
           ? OMIT_SMI_CHECK : INLINE_SMI_CHECK;
   if (access.IsInobject()) {
-    __ sw(value, FieldMemOperand(object, offset));
+    MemOperand operand = FieldMemOperand(object, offset);
+    if (representation.IsByte()) {
+      __ sb(value, operand);
+    } else {
+      __ sw(value, operand);
+    }
     if (instr->hydrogen()->NeedsWriteBarrier()) {
       // Update the write barrier for the object for in-object properties.
       __ RecordWriteField(object,
@@ -4190,7 +4209,12 @@ void LCodeGen::DoStoreNamedField(LStoreNamedField*  
instr) {
     }
   } else {
     __ lw(scratch, FieldMemOperand(object, JSObject::kPropertiesOffset));
-    __ sw(value, FieldMemOperand(scratch, offset));
+    MemOperand operand = FieldMemOperand(scratch, offset);
+    if (representation.IsByte()) {
+      __ sb(value, operand);
+    } else {
+      __ sw(value, operand);
+    }
     if (instr->hydrogen()->NeedsWriteBarrier()) {
       // Update the write barrier for the properties array.
       // object is used as a scratch register.


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