Fuse comparisons that are used by branches together.

runtime/vm/intermediate_language_ia32.cc

Index: runtime/vm/intermediate_language_ia32.cc
diff --git a/runtime/vm/intermediate_language_ia32.cc b/runtime/vm/intermediate_language_ia32.cc
index a07b68266aa6c77c2e1bfa3ad41cd8b46ed1ddd3..0f7e539d967aad2b69294c044735593cee73b264 100644
--- a/runtime/vm/intermediate_language_ia32.cc
+++ b/runtime/vm/intermediate_language_ia32.cc
@@ -31,7 +31,13 @@ LocationSummary* Computation::MakeCallSummary() {
 
 void BindInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   computation()->EmitNativeCode(compiler);
-  __ pushl(locs()->out().reg());
+  if (locs()->out().kind() == Location::kRegister) {
+    // TODO(vegorov): this should really happen only for comparisons fused
+    // with branches.  Currrently IR does not provide an easy way to remove
+    // instructions from the graph so we just leave fused comparison in it
+    // but change its result location to be NoLocation.
+    __ pushl(locs()->out().reg());
+  }
 }
 
 
@@ -163,9 +169,9 @@ void AssertBooleanComp::EmitNativeCode(FlowGraphCompiler* compiler) {
   // Check that the type of the value is allowed in conditional context.
   // Call the runtime if the object is not bool::true or bool::false.
   Label done;
-  __ CompareObject(obj, Bool::ZoneHandle(Bool::True()));
+  __ CompareObject(obj, compiler->bool_true());
   __ j(EQUAL, &done, Assembler::kNearJump);
-  __ CompareObject(obj, Bool::ZoneHandle(Bool::False()));
+  __ CompareObject(obj, compiler->bool_false());
   __ j(EQUAL, &done, Assembler::kNearJump);
 
   __ pushl(Immediate(Smi::RawValue(token_index())));  // Source location.
@@ -186,7 +192,9 @@ LocationSummary* EqualityCompareComp::MakeLocationSummary() const {
   LocationSummary* locs = new LocationSummary(2, 0);
   locs->set_in(0, Location::RequiresRegister());
   locs->set_in(1, Location::RequiresRegister());
-  locs->set_out(Location::RegisterLocation(EAX));
+  if (!is_fused_with_branch()) {
+    locs->set_out(Location::RegisterLocation(EAX));
+  }
   return locs;
 }
 
@@ -194,23 +202,25 @@ LocationSummary* EqualityCompareComp::MakeLocationSummary() const {
 void EqualityCompareComp::EmitNativeCode(FlowGraphCompiler* compiler) {
   Register left = locs()->in(0).reg();
   Register right = locs()->in(1).reg();
-  Register result = locs()->out().reg();
-  ASSERT(locs()->out().reg() == EAX);
 
-  const Bool& bool_true = Bool::ZoneHandle(Bool::True());
-  const Bool& bool_false = Bool::ZoneHandle(Bool::False());
   const Immediate raw_null =
       Immediate(reinterpret_cast<intptr_t>(Object::null()));
-  Label done, load_true, non_null_compare;
+  Label done, non_null_compare;
   __ cmpl(left, raw_null);
   __ j(NOT_EQUAL, &non_null_compare, Assembler::kNearJump);
   // Comparison with NULL is "===".
   __ cmpl(left, right);
-  __ j(EQUAL, &load_true, Assembler::kNearJump);
-  __ LoadObject(result, bool_false);
-  __ jmp(&done, Assembler::kNearJump);
-  __ Bind(&load_true);
-  __ LoadObject(result, bool_true);
+  if (!is_fused_with_branch()) {
+    Register result = locs()->out().reg();
+    Label load_true;
+    __ j(EQUAL, &load_true, Assembler::kNearJump);
+    __ LoadObject(result, compiler->bool_false());
+    __ jmp(&done, Assembler::kNearJump);
+    __ Bind(&load_true);
+    __ LoadObject(result, compiler->bool_true());
+  } else {
+    fused_with_branch()->EmitBranchOnCondition(compiler, EQUAL);
+  }
   __ jmp(&done);
 
   __ Bind(&non_null_compare);
@@ -228,6 +238,13 @@ void EqualityCompareComp::EmitNativeCode(FlowGraphCompiler* compiler) {
                                  kNumberOfArguments,
                                  kNoArgumentNames,
                                  kNumArgumentsChecked);
+  ASSERT(fused_with_branch() != NULL || locs()->out().reg() == EAX);
+
+  if (fused_with_branch() != NULL) {
+    __ CompareObject(EAX, compiler->bool_true());
+    fused_with_branch()->EmitBranchOnCondition(compiler, EQUAL);
+  }
+
   __ Bind(&done);
 }
 
@@ -239,7 +256,9 @@ LocationSummary* RelationalOpComp::MakeLocationSummary() const {
     LocationSummary* summary = new LocationSummary(kNumInputs, kNumTemps);
     summary->set_in(0, Location::RequiresRegister());
     summary->set_in(1, Location::RequiresRegister());
-    summary->set_out(Location::RequiresRegister());
+    if (!is_fused_with_branch()) {
+      summary->set_out(Location::RequiresRegister());
+    }
     summary->set_temp(0, Location::RequiresRegister());
     return summary;
   }
@@ -267,7 +286,6 @@ static void EmitSmiRelationalOp(FlowGraphCompiler* compiler,
                                 RelationalOpComp* comp) {
   Register left = comp->locs()->in(0).reg();
   Register right = comp->locs()->in(1).reg();
-  Register result = comp->locs()->out().reg();
   Register temp = comp->locs()->temp(0).reg();
   Label* deopt = compiler->AddDeoptStub(comp->cid(),
                                         comp->token_index(),
@@ -279,18 +297,23 @@ static void EmitSmiRelationalOp(FlowGraphCompiler* compiler,
   __ orl(temp, right);
   __ testl(temp, Immediate(kSmiTagMask));
   __ j(NOT_ZERO, deopt);
-  const Bool& bool_true = Bool::ZoneHandle(Bool::True());
-  const Bool& bool_false = Bool::ZoneHandle(Bool::False());
-  Condition condition = TokenKindToSmiCondition(comp->kind());
 
-  Label done, is_true;
+  Condition true_condition = TokenKindToSmiCondition(comp->kind());
   __ cmpl(left, right);
-  __ j(condition, &is_true);
-  __ LoadObject(result, bool_false);
-  __ jmp(&done);
-  __ Bind(&is_true);
-  __ LoadObject(result, bool_true);
-  __ Bind(&done);
+
+  if (comp->is_fused_with_branch()) {
+    comp->fused_with_branch()->EmitBranchOnCondition(compiler, true_condition);
+  } else {
+    Register result = comp->locs()->out().reg();
+    Label done, is_true;
+
+    __ j(true_condition, &is_true);
+    __ LoadObject(result, compiler->bool_false());
+    __ jmp(&done);
+    __ Bind(&is_true);
+    __ LoadObject(result, compiler->bool_true());
+    __ Bind(&done);
+  }
 }
 
 
@@ -312,7 +335,6 @@ static void EmitDoubleRelationalOp(FlowGraphCompiler* compiler,
                                    RelationalOpComp* comp) {
   Register left = comp->locs()->in(0).reg();
   Register right = comp->locs()->in(1).reg();
-  Register result = comp->locs()->out().reg();
   // TODO(srdjan): temp is only needed if a conversion Smi->Double occurs.
   Register temp = comp->locs()->temp(0).reg();
   Label* deopt = compiler->AddDeoptStub(comp->cid(),
@@ -323,19 +345,26 @@ static void EmitDoubleRelationalOp(FlowGraphCompiler* compiler,
                                         right);
   compiler->LoadDoubleOrSmiToXmm(XMM0, left, temp, deopt);
   compiler->LoadDoubleOrSmiToXmm(XMM1, right, temp, deopt);
-  const Bool& bool_true = Bool::ZoneHandle(Bool::True());
-  const Bool& bool_false = Bool::ZoneHandle(Bool::False());
+
   Condition true_condition = TokenKindToDoubleCondition(comp->kind());
-  Label is_false, is_true, done;
   __ comisd(XMM0, XMM1);
-  __ j(PARITY_EVEN, &is_false, Assembler::kNearJump);  // NaN -> false;
-  __ j(true_condition, &is_true, Assembler::kNearJump);
-  __ Bind(&is_false);
-  __ LoadObject(result, bool_false);
-  __ jmp(&done);
-  __ Bind(&is_true);
-  __ LoadObject(result, bool_true);
-  __ Bind(&done);
+
+  if (comp->is_fused_with_branch()) {
+    BranchInstr* branch = comp->fused_with_branch();
+    __ j(PARITY_EVEN, compiler->GetBlockLabel(branch->false_successor()));
+    branch->EmitBranchOnCondition(compiler, true_condition);
+  } else {
+    Register result = comp->locs()->out().reg();
+    Label is_false, is_true, done;
+    __ j(PARITY_EVEN, &is_false, Assembler::kNearJump);  // NaN -> false;
+    __ j(true_condition, &is_true, Assembler::kNearJump);
+    __ Bind(&is_false);
+    __ LoadObject(result, compiler->bool_false());
+    __ jmp(&done);
+    __ Bind(&is_true);
+    __ LoadObject(result, compiler->bool_true());
+    __ Bind(&done);
+  }
 }
 
 
@@ -1426,10 +1455,11 @@ void NumberNegateComp::EmitNativeCode(FlowGraphCompiler* compiler) {
 
 LocationSummary* ToDoubleComp::MakeLocationSummary() const {
   const intptr_t kNumInputs = 1;
-  const intptr_t kNumTemps = 1;
   if (from() == kDouble) {
+    const intptr_t kNumTemps = 1;
     LocationSummary* locs = new LocationSummary(kNumInputs, kNumTemps);
     locs->set_in(0, Location::RequiresRegister());
+    locs->set_temp(0, Location::RequiresRegister());
     locs->set_out(Location::SameAsFirstInput());
     return locs;
   } else {