[turbofan] Optimize CheckedInt32Mod with unknown power of 2 right hand side.

src/compiler/effect-control-linearizer.cc

Index: src/compiler/effect-control-linearizer.cc
diff --git a/src/compiler/effect-control-linearizer.cc b/src/compiler/effect-control-linearizer.cc
index 575f050601f36c947a747efe6ef8c5b9417932fc..1b6752ab153c019aa3062cc96c4fb5ae17826281 100644
--- a/src/compiler/effect-control-linearizer.cc
+++ b/src/compiler/effect-control-linearizer.cc
@@ -1285,17 +1285,31 @@ EffectControlLinearizer::LowerCheckedInt32Mod(Node* node, Node* frame_state,
   Node* minusone = jsgraph()->Int32Constant(-1);
   Node* minint = jsgraph()->Int32Constant(std::numeric_limits<int32_t>::min());
 
+  // General case for signed integer modulus, with optimization for (unknown)
+  // power of 2 right hand side.
+  //
+  //   if 0 < rhs then
+  //     msk = rhs - 1
+  //     if rhs & msk == 0 then
+  //       if lhs < 0 then
+  //         -(-lhs & msk)
+  //       else
+  //         lhs & msk
+  //     else
+  //       lhs % rhs
+  //   else
+  //     if rhs < -1 then
+  //       lhs % rhs
+  //     else
+  //       deopt if rhs == 0
+  //       deopt if lhs == minint
+  //       zero
+  //
   Node* lhs = node->InputAt(0);
   Node* rhs = node->InputAt(1);
 
-  // Ensure that {rhs} is not zero, otherwise we'd have to return NaN.
-  Node* check = graph()->NewNode(machine()->Word32Equal(), rhs, zero);
-  control = effect = graph()->NewNode(
-      common()->DeoptimizeIf(DeoptimizeReason::kDivisionByZero), check,
-      frame_state, effect, control);
-
-  // Check if {lhs} is positive or zero.
-  Node* check0 = graph()->NewNode(machine()->Int32LessThanOrEqual(), zero, lhs);
+  // Check if {rhs} is strictly positive.
+  Node* check0 = graph()->NewNode(machine()->Int32LessThan(), zero, rhs);
   Node* branch0 =
       graph()->NewNode(common()->Branch(BranchHint::kTrue), check0, control);
 
@@ -1303,46 +1317,90 @@ EffectControlLinearizer::LowerCheckedInt32Mod(Node* node, Node* frame_state,
   Node* etrue0 = effect;
   Node* vtrue0;
   {
-    // Fast case, no additional checking required.
-    vtrue0 = graph()->NewNode(machine()->Int32Mod(), lhs, rhs, if_true0);
+    Node* msk = graph()->NewNode(machine()->Int32Add(), rhs, minusone);
+
+    // Check if {rhs} minus one is a valid mask.
+    Node* check1 = graph()->NewNode(
+        machine()->Word32Equal(),
+        graph()->NewNode(machine()->Word32And(), rhs, msk), zero);
+    Node* branch1 = graph()->NewNode(common()->Branch(), check1, if_true0);
+
+    Node* if_true1 = graph()->NewNode(common()->IfTrue(), branch1);
+    Node* vtrue1;
+    {
+      // Check if {lhs} is negative.
+      Node* check2 = graph()->NewNode(machine()->Int32LessThan(), lhs, zero);
+      Node* branch2 = graph()->NewNode(common()->Branch(BranchHint::kFalse),
+                                       check2, if_true1);
+
+      // Compute the remainder as {-(-lhs & msk)}.
+      Node* if_true2 = graph()->NewNode(common()->IfTrue(), branch2);
+      Node* vtrue2 = graph()->NewNode(
+          machine()->Int32Sub(), zero,
+          graph()->NewNode(machine()->Word32And(),
+                           graph()->NewNode(machine()->Int32Sub(), zero, lhs),
+                           msk));
+
+      // Compute the remainder as {lhs & msk}.
+      Node* if_false2 = graph()->NewNode(common()->IfFalse(), branch2);
+      Node* vfalse2 = graph()->NewNode(machine()->Word32And(), lhs, msk);
+
+      if_true1 = graph()->NewNode(common()->Merge(2), if_true2, if_false2);
+      vtrue1 =
+          graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
+                           vtrue2, vfalse2, if_true1);
+    }
+
+    // Compute the remainder using the generic {lhs % rhs}.
+    Node* if_false1 = graph()->NewNode(common()->IfFalse(), branch1);
+    Node* vfalse1 =
+        graph()->NewNode(machine()->Int32Mod(), lhs, rhs, if_false1);
+
+    if_true0 = graph()->NewNode(common()->Merge(2), if_true1, if_false1);
+    vtrue0 = graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
+                              vtrue1, vfalse1, if_true0);
   }
 
   Node* if_false0 = graph()->NewNode(common()->IfFalse(), branch0);
   Node* efalse0 = effect;
   Node* vfalse0;
   {
-    // Check if {lhs} is kMinInt and {rhs} is -1, in which case we'd have
-    // to return -0.
-    Node* check1 = graph()->NewNode(machine()->Word32Equal(), lhs, minint);
-    Node* branch1 = graph()->NewNode(common()->Branch(BranchHint::kFalse),
+    // Check if {rhs} is strictly less than -1.
+    Node* check1 = graph()->NewNode(machine()->Int32LessThan(), rhs, minusone);
+    Node* branch1 = graph()->NewNode(common()->Branch(BranchHint::kTrue),
                                      check1, if_false0);
 
+    // Compute the remainder using the generic {lhs % rhs}.
     Node* if_true1 = graph()->NewNode(common()->IfTrue(), branch1);
     Node* etrue1 = efalse0;
-    {
-      // Check if {rhs} is -1.
-      Node* check = graph()->NewNode(machine()->Word32Equal(), rhs, minusone);
-      if_true1 = etrue1 =
-          graph()->NewNode(common()->DeoptimizeIf(DeoptimizeReason::kMinusZero),
-                           check, frame_state, etrue1, if_true1);
-    }
+    Node* vtrue1 = graph()->NewNode(machine()->Int32Mod(), lhs, rhs, if_true1);
 
     Node* if_false1 = graph()->NewNode(common()->IfFalse(), branch1);
     Node* efalse1 = efalse0;
+    Node* vfalse1;
+    {
+      // Ensure that {rhs} is not zero.
+      Node* check2 = graph()->NewNode(machine()->Word32Equal(), rhs, zero);
+      if_false1 = efalse1 = graph()->NewNode(
+          common()->DeoptimizeIf(DeoptimizeReason::kDivisionByZero), check2,
+          frame_state, efalse1, if_false1);
+
+      // Now we know that {rhs} is -1, so make sure {lhs} is not kMinInt, as
+      // we would otherwise have to return -0.
+      Node* check3 = graph()->NewNode(machine()->Word32Equal(), lhs, minint);
+      if_false1 = efalse1 =
+          graph()->NewNode(common()->DeoptimizeIf(DeoptimizeReason::kMinusZero),
+                           check3, frame_state, efalse1, if_false1);
+
+      // The remainder is zero.
+      vfalse1 = zero;
+    }
 
     if_false0 = graph()->NewNode(common()->Merge(2), if_true1, if_false1);
     efalse0 =
         graph()->NewNode(common()->EffectPhi(2), etrue1, efalse1, if_false0);
-
-    // Perform the actual integer modulos.
-    vfalse0 = graph()->NewNode(machine()->Int32Mod(), lhs, rhs, if_false0);
-
-    // Check if the result is zero, because in that case we'd have to return
-    // -0 here since we always take the signe of the {lhs} which is negative.
-    Node* check = graph()->NewNode(machine()->Word32Equal(), vfalse0, zero);
-    if_false0 = efalse0 =
-        graph()->NewNode(common()->DeoptimizeIf(DeoptimizeReason::kMinusZero),
-                         check, frame_state, efalse0, if_false0);
+    vfalse0 = graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
+                               vtrue1, vfalse1, if_false0);
   }
 
   control = graph()->NewNode(common()->Merge(2), if_true0, if_false0);