MIPS: Improve code generation for bounds checks.

Port r20872 (0e79653)

BUG=
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/246253007

Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20892 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/lithium-codegen-mips.cc

@@ -4162,42 +4162,25 @@ void LCodeGen::DoStoreNamedGeneric(LStoreNamedGeneric* instr) {
 }
 
 
-void LCodeGen::ApplyCheckIf(Condition condition,
-                            LBoundsCheck* check,
-                            Register src1,
-                            const Operand& src2) {
-  if (FLAG_debug_code && check->hydrogen()->skip_check()) {
+void LCodeGen::DoBoundsCheck(LBoundsCheck* instr) {
+  Condition cc = instr->hydrogen()->allow_equality() ? hi : hs;
+  Operand operand(0);
+  Register reg;
+  if (instr->index()->IsConstantOperand()) {
+    operand = ToOperand(instr->index());
+    reg = ToRegister(instr->length());
+    cc = ReverseCondition(cc);
+  } else {
+    reg = ToRegister(instr->index());
+    operand = ToOperand(instr->length());
+  }
+  if (FLAG_debug_code && instr->hydrogen()->skip_check()) {
     Label done;
-    __ Branch(&done, NegateCondition(condition), src1, src2);
+    __ Branch(&done, NegateCondition(cc), reg, operand);
     __ stop("eliminated bounds check failed");
     __ bind(&done);
   } else {
-    DeoptimizeIf(condition, check->environment(), src1, src2);
-  }
-}
-
-
-void LCodeGen::DoBoundsCheck(LBoundsCheck* instr) {
-  if (instr->hydrogen()->skip_check()) return;
-
-  Condition condition = instr->hydrogen()->allow_equality() ? hi : hs;
-  if (instr->index()->IsConstantOperand()) {
-    int constant_index =
-        ToInteger32(LConstantOperand::cast(instr->index()));
-    if (instr->hydrogen()->length()->representation().IsSmi()) {
-      __ li(at, Operand(Smi::FromInt(constant_index)));
-    } else {
-      __ li(at, Operand(constant_index));
-    }
-    ApplyCheckIf(condition,
-                 instr,
-                 at,
-                 Operand(ToRegister(instr->length())));
-  } else {
-    ApplyCheckIf(condition,
-                 instr,
-                 ToRegister(instr->index()),
-                 Operand(ToRegister(instr->length())));
+    DeoptimizeIf(cc, instr->environment(), reg, operand);
   }
 }
 

src/mips/lithium-codegen-mips.h

@@ -263,10 +263,6 @@ class LCodeGen: public LCodeGenBase {
                     LEnvironment* environment,
                     Register src1 = zero_reg,
                     const Operand& src2 = Operand(zero_reg));
-  void ApplyCheckIf(Condition condition,
-                    LBoundsCheck* check,
-                    Register src1 = zero_reg,
-                    const Operand& src2 = Operand(zero_reg));
 
   void AddToTranslation(LEnvironment* environment,
                         Translation* translation,

src/mips/lithium-mips.cc

@@ -1782,9 +1782,16 @@ LInstruction* LChunkBuilder::DoSeqStringSetChar(HSeqStringSetChar* instr) {
 
 
 LInstruction* LChunkBuilder::DoBoundsCheck(HBoundsCheck* instr) {
-  LOperand* value = UseRegisterOrConstantAtStart(instr->index());
-  LOperand* length = UseRegister(instr->length());
-  return AssignEnvironment(new(zone()) LBoundsCheck(value, length));
+  if (!FLAG_debug_code && instr->skip_check()) return NULL;
+  LOperand* index = UseRegisterOrConstantAtStart(instr->index());
+  LOperand* length = !index->IsConstantOperand()
+  ? UseRegisterOrConstantAtStart(instr->length())
+  : UseRegisterAtStart(instr->length());
+  LInstruction* result = new(zone()) LBoundsCheck(index, length);
+  if (!FLAG_debug_code || !instr->skip_check()) {
+    result = AssignEnvironment(result);
+  }
+  return result;
 }
 
 

src/mips/macro-assembler-mips.cc

@@ -2091,7 +2091,7 @@ void MacroAssembler::BranchShort(Label* L, Condition cond, Register rs,
       case Uless_equal:
         if (rt.imm32_ == 0) {
           offset = shifted_branch_offset(L, false);
-          b(offset);
+          beq(rs, zero_reg, offset);
         } else {
           ASSERT(!scratch.is(rs));
           r2 = scratch;