PPC: [compiler] Remove broken support for undetectable strings.

Port b62dbf1e

Original commit message:
    Support for undetectable strings was officially dropped in
    https://codereview.chromium.org/916753002, but the compilers
    weren't fixed properly.

R=bmeurer@chromium.org, jyan@ca.ibm.com, dstence@us.ibm.com, joransiu@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1312473012

Cr-Commit-Position: refs/heads/master@{#30390}

src/full-codegen/ppc/full-codegen-ppc.cc

@@ -4992,13 +4992,8 @@ void FullCodeGenerator::EmitLiteralCompareTypeof(Expression* expr,
     Split(eq, if_true, if_false, fall_through);
   } else if (String::Equals(check, factory->string_string())) {
     __ JumpIfSmi(r3, if_false);
-    // Check for undetectable objects => false.
     __ CompareObjectType(r3, r3, r4, FIRST_NONSTRING_TYPE);
-    __ bge(if_false);
-    __ lbz(r4, FieldMemOperand(r3, Map::kBitFieldOffset));
-    STATIC_ASSERT((1 << Map::kIsUndetectable) < 0x8000);
-    __ andi(r0, r4, Operand(1 << Map::kIsUndetectable));
-    Split(eq, if_true, if_false, fall_through, cr0);
+    Split(lt, if_true, if_false, fall_through);
   } else if (String::Equals(check, factory->symbol_string())) {
     __ JumpIfSmi(r3, if_false);
     __ CompareObjectType(r3, r3, r4, SYMBOL_TYPE);

src/ppc/lithium-codegen-ppc.cc

@@ -5903,11 +5903,7 @@ Condition LCodeGen::EmitTypeofIs(Label* true_label, Label* false_label,
   } else if (String::Equals(type_name, factory->string_string())) {
     __ JumpIfSmi(input, false_label);
     __ CompareObjectType(input, scratch, no_reg, FIRST_NONSTRING_TYPE);
-    __ bge(false_label);
-    __ lbz(scratch, FieldMemOperand(scratch, Map::kBitFieldOffset));
-    __ ExtractBit(r0, scratch, Map::kIsUndetectable);
-    __ cmpi(r0, Operand::Zero());
-    final_branch_condition = eq;
+    final_branch_condition = lt;
 
   } else if (String::Equals(type_name, factory->symbol_string())) {
     __ JumpIfSmi(input, false_label);