[compiler] Better code generation for branches on binops

Commit 0719ace6 improves the code
generated for comparisons by avoiding the materalization of the
comparison bit.

Now, this commit aims at doing this same improvement for binary
operations. Since binary operations set the ZF flag, there is no
reason to insert a "== 0" comparison.

Note that this commit might increase register pressure, which might
actually reduce performance. It's hard to anticipate, so we'll land
it, and revert it if it's actually bad for performance.


Bug: v8:12484
Change-Id: I963f0c4afdd59b35b4bac468e47d987836433163
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3545165Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Darius Mercadier <dmercadier@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79611}

src/compiler/branch-condition-duplicator.cc

@@ -18,15 +18,29 @@ namespace {
 bool IsBranch(Node* node) { return node->opcode() == IrOpcode::kBranch; }
 
 bool CanDuplicate(Node* node) {
-  // We only allow duplication of comparisons. Duplicating other nodes makes
-  // little sense, because a "== 0" need to be inserted in branches anyways
-  // (except for some binops, but duplicating binops might increase the live
-  // range  of the operands, thus increasing register pressure).
+  // We only allow duplication of comparisons and "cheap" binary operations
+  // (cheap = not multiplication or division). The idea is that those
+  // instructions set the ZF flag, and thus do not require a "== 0" to be added
+  // before the branch. Duplicating other nodes, on the other hand, makes little
+  // sense, because a "== 0" would need to be inserted in branches anyways.
   switch (node->opcode()) {
 #define BRANCH_CASE(op) \
   case IrOpcode::k##op: \
     break;
     MACHINE_COMPARE_BINOP_LIST(BRANCH_CASE)
+    case IrOpcode::kInt32Add:
+    case IrOpcode::kInt32Sub:
+    case IrOpcode::kWord32And:
+    case IrOpcode::kWord32Or:
+    case IrOpcode::kInt64Add:
+    case IrOpcode::kInt64Sub:
+    case IrOpcode::kWord64And:
+    case IrOpcode::kWord64Or:
+    case IrOpcode::kWord32Shl:
+    case IrOpcode::kWord32Shr:
+    case IrOpcode::kWord64Shl:
+    case IrOpcode::kWord64Shr:
+      break;
     default:
       return false;
   }