Reviewers: Benedikt Meurer,
Description:
[turbofan] Factor out common code between ReduceSelect and ReduceBranch in
ControlReducer.
[email protected]
BUG=
Please review this at https://codereview.chromium.org/734593003/
Base URL: https://chromium.googlesource.com/v8/v8.git@master
Affected files (+25, -40 lines):
M src/compiler/control-reducer.cc
Index: src/compiler/control-reducer.cc
diff --git a/src/compiler/control-reducer.cc
b/src/compiler/control-reducer.cc
index
1d8310316e7219bdc518fd465c9eab43052b7b43..b5acbb23e7abb6e19d509f6996b37e7930102823
100644
--- a/src/compiler/control-reducer.cc
+++ b/src/compiler/control-reducer.cc
@@ -16,6 +16,7 @@ namespace compiler {
enum VisitState { kUnvisited = 0, kOnStack = 1, kRevisit = 2, kVisited = 3
};
enum Reachability { kFromStart = 8 };
+enum Decision { kFalse, kUnknown, kTrue };
#define TRACE(x) \
if (FLAG_trace_turbo_reduction) PrintF x
@@ -340,29 +341,37 @@ class ControlReducerImpl {
}
}
- // Reduce redundant selects.
- Node* ReduceSelect(Node* const node) {
- Node* const cond = node->InputAt(0);
- Node* const tvalue = node->InputAt(1);
- Node* const fvalue = node->InputAt(2);
- if (tvalue == fvalue) return tvalue;
+ // Try to statically fold a condition.
+ Decision DecideCondition(Node* cond) {
switch (cond->opcode()) {
case IrOpcode::kInt32Constant:
- return Int32Matcher(cond).Is(0) ? fvalue : tvalue;
+ return Int32Matcher(cond).Is(0) ? kFalse : kTrue;
case IrOpcode::kInt64Constant:
- return Int64Matcher(cond).Is(0) ? fvalue : tvalue;
+ return Int64Matcher(cond).Is(0) ? kFalse : kTrue;
case IrOpcode::kNumberConstant:
- return NumberMatcher(cond).Is(0) ? fvalue : tvalue;
+ return NumberMatcher(cond).Is(0) ? kFalse : kTrue;
case IrOpcode::kHeapConstant: {
Handle<Object> object =
HeapObjectMatcher<Object>(cond).Value().handle();
- if (object->IsTrue()) return tvalue;
- if (object->IsFalse()) return fvalue;
+ if (object->IsTrue()) return kTrue;
+ if (object->IsFalse()) return kFalse;
+ // TODO(turbofan): decide more conditions for heap constants.
break;
}
default:
break;
}
+ return kUnknown;
+ }
+
+ // Reduce redundant selects.
+ Node* ReduceSelect(Node* const node) {
+ Node* const tvalue = node->InputAt(1);
+ Node* const fvalue = node->InputAt(2);
+ if (tvalue == fvalue) return tvalue;
+ Decision result = DecideCondition(node->InputAt(0));
+ if (result == kTrue) return tvalue;
+ if (result == kFalse) return fvalue;
return node;
}
@@ -436,35 +445,11 @@ class ControlReducerImpl {
// Reduce branches if they have constant inputs.
Node* ReduceBranch(Node* node) {
- Node* cond = node->InputAt(0);
- bool is_true;
- switch (cond->opcode()) {
- case IrOpcode::kInt32Constant:
- is_true = !Int32Matcher(cond).Is(0);
- break;
- case IrOpcode::kInt64Constant:
- is_true = !Int64Matcher(cond).Is(0);
- break;
- case IrOpcode::kNumberConstant:
- is_true = !NumberMatcher(cond).Is(0);
- break;
- case IrOpcode::kHeapConstant: {
- Handle<Object> object =
- HeapObjectMatcher<Object>(cond).Value().handle();
- if (object->IsTrue())
- is_true = true;
- else if (object->IsFalse())
- is_true = false;
- else
- return node; // TODO(turbofan): fold branches on strings,
objects.
- break;
- }
- default:
- return node;
- }
+ Decision result = DecideCondition(node->InputAt(0));
+ if (result == kUnknown) return node;
TRACE(("BranchReduce: #%d:%s = %s\n", node->id(),
node->op()->mnemonic(),
- is_true ? "true" : "false"));
+ (result == kTrue) ? "true" : "false"));
// Replace IfTrue and IfFalse projections from this branch.
Node* control = NodeProperties::GetControlInput(node);
@@ -473,11 +458,11 @@ class ControlReducerImpl {
if (to->opcode() == IrOpcode::kIfTrue) {
TRACE((" IfTrue: #%d:%s\n", to->id(), to->op()->mnemonic()));
i.UpdateToAndIncrement(NULL);
- ReplaceNode(to, is_true ? control : dead());
+ ReplaceNode(to, (result == kTrue) ? control : dead());
} else if (to->opcode() == IrOpcode::kIfFalse) {
TRACE((" IfFalse: #%d:%s\n", to->id(), to->op()->mnemonic()));
i.UpdateToAndIncrement(NULL);
- ReplaceNode(to, is_true ? dead() : control);
+ ReplaceNode(to, (result == kTrue) ? dead() : control);
} else {
++i;
}
--
--
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