MIPS: Let NaN flow as double into HBranch + some minor improvements

Port r15246 (cb18dce2)

BUG=
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/17198012

Patch from Akos Palfi <palfia@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15259 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/lithium-codegen-mips.cc

@@ -2039,10 +2039,23 @@ void LCodeGen::DoBranch(LBranch* instr) {
     } else if (type.IsSmi()) {
       ASSERT(!info()->IsStub());
       EmitBranch(instr, ne, reg, Operand(zero_reg));
+    } else if (type.IsJSArray()) {
+      ASSERT(!info()->IsStub());
+      EmitBranch(instr, al, zero_reg, Operand(zero_reg));
+    } else if (type.IsHeapNumber()) {
+      ASSERT(!info()->IsStub());
+      DoubleRegister dbl_scratch = double_scratch0();
+      __ ldc1(dbl_scratch, FieldMemOperand(reg, HeapNumber::kValueOffset));
+      // Test the double value. Zero and NaN are false.
+      EmitBranchF(instr, nue, dbl_scratch, kDoubleRegZero);
+    } else if (type.IsString()) {
+      ASSERT(!info()->IsStub());
+      __ lw(at, FieldMemOperand(reg, String::kLengthOffset));
+      EmitBranch(instr, ne, at, Operand(zero_reg));
     } else {
       ToBooleanStub::Types expected = instr->hydrogen()->expected_input_types();
       // Avoid deopts in the case where we've never executed this path before.
-      if (expected.IsEmpty()) expected = ToBooleanStub::all_types();
+      if (expected.IsEmpty()) expected = ToBooleanStub::Types::Generic();
 
       if (expected.Contains(ToBooleanStub::UNDEFINED)) {
         // undefined -> false.
@@ -2122,8 +2135,11 @@ void LCodeGen::DoBranch(LBranch* instr) {
         __ bind(&not_heap_number);
       }
 
-      // We've seen something for the first time -> deopt.
-      DeoptimizeIf(al, instr->environment(), zero_reg, Operand(zero_reg));
+      if (!expected.IsGeneric()) {
+        // We've seen something for the first time -> deopt.
+        // This can only happen if we are not generic already.
+        DeoptimizeIf(al, instr->environment(), zero_reg, Operand(zero_reg));
+      }
     }
   }
 }

src/mips/lithium-mips.cc

@@ -1003,10 +1003,13 @@ LInstruction* LChunkBuilder::DoBranch(HBranch* instr) {
 
   LBranch* result = new(zone()) LBranch(UseRegister(value));
   // Tagged values that are not known smis or booleans require a
-  // deoptimization environment.
+  // deoptimization environment. If the instruction is generic no
+  // environment is needed since all cases are handled.
   Representation rep = value->representation();
   HType type = value->type();
-  if (rep.IsTagged() && !type.IsSmi() && !type.IsBoolean()) {
+  ToBooleanStub::Types expected = instr->expected_input_types();
+  if (rep.IsTagged() && !type.IsSmi() && !type.IsBoolean() &&
+      !expected.IsGeneric()) {
     return AssignEnvironment(result);
   }
   return result;