Reviewers: dcarney,
Description:
[turbofan] Fix simplified lowering of Int32Div.
Optimize for the common case and get rid of the unreadable Diamond
helper code there.
[email protected]
Please review this at https://codereview.chromium.org/954173002/
Base URL: https://chromium.googlesource.com/v8/v8.git@master
Affected files (+54, -12 lines):
M src/compiler/simplified-lowering.cc
Index: src/compiler/simplified-lowering.cc
diff --git a/src/compiler/simplified-lowering.cc
b/src/compiler/simplified-lowering.cc
index
59dd741ee476f875aa9643e0213ef3bfabe9eea1..65e070696be3f863666e5fe0bd1363c4fa332367
100644
--- a/src/compiler/simplified-lowering.cc
+++ b/src/compiler/simplified-lowering.cc
@@ -1311,6 +1311,7 @@ Node* SimplifiedLowering::StringComparison(Node*
node, bool requires_ordering) {
Node* SimplifiedLowering::Int32Div(Node* const node) {
Int32BinopMatcher m(node);
Node* const zero = jsgraph()->Int32Constant(0);
+ Node* const minus_one = jsgraph()->Int32Constant(-1);
Node* const lhs = m.left().node();
Node* const rhs = m.right().node();
@@ -1322,20 +1323,61 @@ Node* SimplifiedLowering::Int32Div(Node* const
node) {
return graph()->NewNode(machine()->Int32Div(), lhs, rhs,
graph()->start());
}
- Diamond if_zero(graph(), common(),
- graph()->NewNode(machine()->Word32Equal(), rhs, zero),
- BranchHint::kFalse);
+ // General case for signed integer division.
+ //
+ // if 0 < rhs then
+ // lhs / rhs
+ // else
+ // if rhs < -1 then
+ // lhs / rhs
+ // else if rhs == 0 then
+ // 0
+ // else
+ // 0 - lhs
+ //
+ // Note: We do not use the Diamond helper class here, because it really
hurts
+ // readability with nested diamonds.
+ const Operator* const merge_op = common()->Merge(2);
+ const Operator* const phi_op = common()->Phi(kMachInt32, 2);
- Diamond if_minus_one(graph(), common(),
- graph()->NewNode(machine()->Word32Equal(), rhs,
- jsgraph()->Int32Constant(-1)),
- BranchHint::kFalse);
- if_minus_one.Nest(if_zero, false);
- Node* sub = graph()->NewNode(machine()->Int32Sub(), zero, lhs);
- Node* div =
- graph()->NewNode(machine()->Int32Div(), lhs, rhs,
if_minus_one.if_false);
+ Node* check0 = graph()->NewNode(machine()->Int32LessThan(), zero, rhs);
+ Node* branch0 = graph()->NewNode(common()->Branch(BranchHint::kTrue),
check0,
+ graph()->start());
+
+ Node* if_true0 = graph()->NewNode(common()->IfTrue(), branch0);
+ Node* true0 = graph()->NewNode(machine()->Int32Div(), lhs, rhs,
if_true0);
+
+ Node* if_false0 = graph()->NewNode(common()->IfFalse(), branch0);
+ Node* false0;
+ {
+ Node* check1 = graph()->NewNode(machine()->Int32LessThan(), rhs,
minus_one);
+ Node* branch1 = graph()->NewNode(common()->Branch(), check1,
if_false0);
+
+ Node* if_true1 = graph()->NewNode(common()->IfTrue(), branch1);
+ Node* true1 = graph()->NewNode(machine()->Int32Div(), lhs, rhs,
if_true1);
- return if_zero.Phi(kMachInt32, zero, if_minus_one.Phi(kMachInt32, sub,
div));
+ Node* if_false1 = graph()->NewNode(common()->IfFalse(), branch1);
+ Node* false1;
+ {
+ Node* check2 = graph()->NewNode(machine()->Word32Equal(), rhs, zero);
+ Node* branch2 = graph()->NewNode(common()->Branch(), check2,
if_false1);
+
+ Node* if_true2 = graph()->NewNode(common()->IfTrue(), branch2);
+ Node* true2 = zero;
+
+ Node* if_false2 = graph()->NewNode(common()->IfFalse(), branch2);
+ Node* false2 = graph()->NewNode(machine()->Int32Sub(), zero, lhs);
+
+ if_false1 = graph()->NewNode(merge_op, if_true2, if_false2);
+ false1 = graph()->NewNode(phi_op, true2, false2, if_false1);
+ }
+
+ if_false0 = graph()->NewNode(merge_op, if_true1, if_false1);
+ false0 = graph()->NewNode(phi_op, true1, false1, if_false0);
+ }
+
+ Node* merge0 = graph()->NewNode(merge_op, if_true0, if_false0);
+ return graph()->NewNode(phi_op, true0, false0, merge0);
}
--
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