X87: Convert String array index/length hash to BitField.

Port r21533 (736c779)

BUG=
R=danno@chromium.org

Review URL: https://codereview.chromium.org/298293007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21549 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

diff --git a/src/x87/macro-assembler-x87.cc b/src/x87/macro-assembler-x87.cc
index 8d8876f..bd5c623 100644 (file)
--- a/src/x87/macro-assembler-x87.cc
+++ b/src/x87/macro-assembler-x87.cc
@@ -1940,16 +1940,10 @@ void MacroAssembler::IndexFromHash(Register hash, Register index) {
   // reserved for it does not conflict.
   ASSERT(TenToThe(String::kMaxCachedArrayIndexLength) <
          (1 << String::kArrayIndexValueBits));
-  // We want the smi-tagged index in key.  kArrayIndexValueMask has zeros in
-  // the low kHashShift bits.
-  and_(hash, String::kArrayIndexValueMask);
-  STATIC_ASSERT(String::kHashShift >= kSmiTagSize && kSmiTag == 0);
-  if (String::kHashShift > kSmiTagSize) {
-    shr(hash, String::kHashShift - kSmiTagSize);
-  }
   if (!index.is(hash)) {
     mov(index, hash);
   }
+  DecodeFieldToSmi<String::ArrayIndexValueBits>(index);
 }
 
 

diff --git a/src/x87/macro-assembler-x87.h b/src/x87/macro-assembler-x87.h
index 8f04ac3..faa9012 100644 (file)
--- a/src/x87/macro-assembler-x87.h
+++ b/src/x87/macro-assembler-x87.h
@@ -478,7 +478,23 @@ class MacroAssembler: public Assembler {
   void DecodeField(Register reg) {
     static const int shift = Field::kShift;
     static const int mask = Field::kMask >> Field::kShift;
-    sar(reg, shift);
+    if (shift != 0) {
+      sar(reg, shift);
+    }
+    and_(reg, Immediate(mask));
+  }
+
+  template<typename Field>
+  void DecodeFieldToSmi(Register reg) {
+    static const int shift = Field::kShift;
+    static const int mask = (Field::kMask >> Field::kShift) << kSmiTagSize;
+    STATIC_ASSERT((mask & (0x80000000u >> (kSmiTagSize - 1))) == 0);
+    STATIC_ASSERT(kSmiTag == 0);
+    if (shift < kSmiTagSize) {
+      shl(reg, kSmiTagSize - shift);
+    } else if (shift > kSmiTagSize) {
+      sar(reg, shift - kSmiTagSize);
+    }
     and_(reg, Immediate(mask));
   }