Improve generated MIPS code for conditional expressions and branches by delaying

runtime/vm/flow_graph_compiler_mips.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_MIPS.
 #if defined(TARGET_ARCH_MIPS)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 1377 matching lines @@
   __ Drop(argument_count);
 }
 
 
 Condition FlowGraphCompiler::EmitEqualityRegConstCompare(
     Register reg,
     const Object& obj,
     bool needs_number_check,
     intptr_t token_pos) {
   __ TraceSimMsg("EqualityRegConstCompare");
+  ASSERT(!needs_number_check ||
+         (!obj.IsMint() && !obj.IsDouble() && !obj.IsBigint()));
   if (needs_number_check) {
     StubCode* stub_code = isolate()->stub_code();
     ASSERT(!obj.IsMint() && !obj.IsDouble() && !obj.IsBigint());
     __ addiu(SP, SP, Immediate(-2 * kWordSize));
     __ sw(reg, Address(SP, 1 * kWordSize));
     __ LoadObject(TMP, obj);
     __ sw(TMP, Address(SP, 0 * kWordSize));
     if (is_optimizing()) {
       __ BranchLinkPatchable(
           &stub_code->OptimizedIdenticalWithNumberCheckLabel());
     } else {
       __ BranchLinkPatchable(
           &stub_code->UnoptimizedIdenticalWithNumberCheckLabel());
     }
     if (token_pos != Scanner::kNoSourcePos) {
       AddCurrentDescriptor(RawPcDescriptors::kRuntimeCall,
                            Isolate::kNoDeoptId,
                            token_pos);
     }
     __ TraceSimMsg("EqualityRegConstCompare return");
-    // Stub returns result in CMPRES1 (if it is 0, then reg and obj are
-    // equal) and always sets CMPRES2 to 0.
+    // Stub returns result in CMPRES1 (if it is 0, then reg and obj are equal).
     __ lw(reg, Address(SP, 1 * kWordSize));  // Restore 'reg'.
     __ addiu(SP, SP, Immediate(2 * kWordSize));  // Discard constant.
+    return Condition(CMPRES1, ZR, EQ);
   } else {
-    __ CompareObject(CMPRES1, CMPRES2, reg, obj);
+    int16_t imm = 0;
+    const Register obj_reg = __ LoadConditionOperand(CMPRES1, obj, &imm);
+    return Condition(reg, obj_reg, EQ, imm);
   }
-  return EQ;
 }
 
 
 Condition FlowGraphCompiler::EmitEqualityRegRegCompare(Register left,
                                                        Register right,
                                                        bool needs_number_check,
                                                        intptr_t token_pos) {
   __ TraceSimMsg("EqualityRegRegCompare");
   __ Comment("EqualityRegRegCompare");
   if (needs_number_check) {
@@ skipping 15 matching lines @@
     }
 #if defined(DEBUG)
     if (!is_optimizing()) {
       // Do this *after* adding the pc descriptor!
       __ LoadImmediate(S4, kInvalidObjectPointer);
       __ LoadImmediate(S5, kInvalidObjectPointer);
     }
 #endif
     __ TraceSimMsg("EqualityRegRegCompare return");
     // Stub returns result in CMPRES1 (if it is 0, then left and right are
-    // equal) and always sets CMPRES2 to 0.
+    // equal).
     __ lw(right, Address(SP, 0 * kWordSize));
     __ lw(left, Address(SP, 1 * kWordSize));
     __ addiu(SP, SP, Immediate(2 * kWordSize));
+    return Condition(CMPRES1, ZR, EQ);
   } else {
-    __ slt(CMPRES1, left, right);
-    __ slt(CMPRES2, right, left);
+    return Condition(left, right, EQ);
   }
-  return EQ;
 }
 
 
 // This function must be in sync with FlowGraphCompiler::RecordSafepoint and
 // FlowGraphCompiler::SlowPathEnvironmentFor.
 void FlowGraphCompiler::SaveLiveRegisters(LocationSummary* locs) {
 #if defined(DEBUG)
   locs->CheckWritableInputs();
   ClobberDeadTempRegisters(locs);
 #endif
@@ skipping 381 matching lines @@
   __ AddImmediate(SP, kDoubleSize);
 }
 
 
 #undef __
 
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_MIPS