[turbofan] Fix input count in Uint32Mod/Div reduction.

src/compiler/machine-operator-reducer.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/machine-operator-reducer.h"
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/codegen.h"
 #include "src/compiler/generic-node-inl.h"
@@ skipping 582 matching lines @@
   if (m.right().Is(1)) return Replace(m.left().node());   // x / 1 => x
   if (m.IsFoldable()) {                                   // K / K => K
     return ReplaceUint32(
         base::bits::UnsignedDiv32(m.left().Value(), m.right().Value()));
   }
   if (m.LeftEqualsRight()) {  // x / x => x != 0
     Node* const zero = Int32Constant(0);
     return Replace(Word32Equal(Word32Equal(m.left().node(), zero), zero));
   }
   if (m.right().IsPowerOf2()) {  // x / 2^n => x >> n
+    node->ReplaceInput(1, Uint32Constant(WhichPowerOf2(m.right().Value())));

[Benedikt Meurer, 2014/10/29 18:26:45]

Let's keep the set_op() before ReplaceInput.

[Jarin, 2014/10/29 21:12:24]

Done.

I am wondering what's the reason for this. I was always imagining that the
set_op method should be the operation that morally 'commits' the changes to the
node. E.g., if we want to hook up the typer for re-typing, set_op would be the
method to do that. (Well, we would have to make set_op a method on the graph,
but you get the idea.)

+    node->TrimInputCount(2);
     node->set_op(machine()->Word32Shr());
-    node->ReplaceInput(1, Uint32Constant(WhichPowerOf2(m.right().Value())));
     return Changed(node);
   }
   return NoChange();
 }
 
 
 Reduction MachineOperatorReducer::ReduceInt32Mod(Node* node) {
   Int32BinopMatcher m(node);
   if (m.left().Is(0)) return Replace(m.left().node());    // 0 % x  => 0
   if (m.right().Is(0)) return Replace(m.right().node());  // x % 0  => 0
@@ skipping 43 matching lines @@
   Uint32BinopMatcher m(node);
   if (m.left().Is(0)) return Replace(m.left().node());    // 0 % x => 0
   if (m.right().Is(0)) return Replace(m.right().node());  // x % 0 => 0
   if (m.right().Is(1)) return ReplaceUint32(0);           // x % 1 => 0
   if (m.LeftEqualsRight()) return ReplaceInt32(0);        // x % x  => 0
   if (m.IsFoldable()) {                                   // K % K => K
     return ReplaceUint32(
         base::bits::UnsignedMod32(m.left().Value(), m.right().Value()));
   }
   if (m.right().IsPowerOf2()) {  // x % 2^n => x & 2^n-1
+    node->ReplaceInput(1, Uint32Constant(m.right().Value() - 1));
+    node->TrimInputCount(2);
     node->set_op(machine()->Word32And());

[Benedikt Meurer, 2014/10/29 18:26:45]

Same here.

[Jarin, 2014/10/29 21:12:24]

Done.

-    node->ReplaceInput(1, Uint32Constant(m.right().Value() - 1));
     return Changed(node);
   }
   return NoChange();
 }
 
 
 Reduction MachineOperatorReducer::ReduceProjection(size_t index, Node* node) {
   switch (node->opcode()) {
     case IrOpcode::kInt32AddWithOverflow: {
       DCHECK(index == 0 || index == 1);
@@ skipping 38 matching lines @@
 MachineOperatorBuilder* MachineOperatorReducer::machine() const {
   return jsgraph()->machine();
 }
 
 
 Graph* MachineOperatorReducer::graph() const { return jsgraph()->graph(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8