commit 71a9fcc950f1b8efb27543961745ab0262cda7c4
author Darius Mercadier <dmercadier@chromium.org> Mon Mar 14 16:46:57 2022
committer V8 LUCI CQ <v8-scoped@luci-project-accounts.iam.gserviceaccount.com> Mon Mar 14 17:33:05 2022
tree ce8ff049c30cf0ae252fc9f7a16891bb465d4c5c
parent dc9ed94efdac30bdbe88e81f4cf08783c1dc952f

Revert "[compiler] let InstructionSelector duplicate branch conditions"

This reverts commit 3d5d99ffd9bd0dd433cfdf8ba9b207648ff51ea9.

Reason for revert: causes this crash: https://bugs.chromium.org/p/chromium/issues/detail?id=1303458

Original change's description:
> [compiler] let InstructionSelector duplicate branch conditions
>
> Bug: v8:12484
> Change-Id: I44c2028efadbd70e7711f01d107995e0462f05d4
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3477094
> Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
> Commit-Queue: Darius Mercadier <dmercadier@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#79239}

Bug: chromium:1303458, v8:12484
Change-Id: I129467bcb2507f2fba894f5dd58304eb139f739c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3522069
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Darius Mercadier <dmercadier@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79469}

src/compiler/backend/x64/instruction-selector-x64.cc

diff --git a/src/compiler/backend/x64/instruction-selector-x64.cc b/src/compiler/backend/x64/instruction-selector-x64.cc
index 2cc4bef..a30b501 100644
--- a/src/compiler/backend/x64/instruction-selector-x64.cc
+++ b/src/compiler/backend/x64/instruction-selector-x64.cc
@@ -2479,28 +2479,6 @@
   selector->Emit(code, arraysize(outputs), outputs, arraysize(inputs), inputs);
 }
 
-// Used instead of CanCover in VisitWordCompareZero: even if CanCover(user,
-// node) returns false, if |node| is a comparison, then it does not require any
-// registers, and can thus be covered by |user|.
-bool CanCoverForCompareZero(InstructionSelector* selector, Node* user,
-                            Node* node) {
-  if (selector->CanCover(user, node)) {
-    return true;
-  }
-  // Checking if |node| is a comparison. If so, it doesn't required any
-  // registers, and, as such, it can always be covered by |user|.
-  switch (node->opcode()) {
-#define CHECK_CMP_OP(op) \
-  case IrOpcode::k##op:  \
-    return true;
-    MACHINE_COMPARE_BINOP_LIST(CHECK_CMP_OP)
-#undef CHECK_CMP_OP
-    default:
-      break;
-  }
-  return false;
-}
-
 }  // namespace
 
 // Shared routine for word comparison against zero.
@@ -2516,7 +2494,7 @@
     cont->Negate();
   }
 
-  if (CanCoverForCompareZero(this, user, value)) {
+  if (CanCover(user, value)) {
     switch (value->opcode()) {
       case IrOpcode::kWord32Equal:
         cont->OverwriteAndNegateIfEqual(kEqual);
@@ -2536,7 +2514,7 @@
       case IrOpcode::kWord64Equal: {
         cont->OverwriteAndNegateIfEqual(kEqual);
         Int64BinopMatcher m(value);
-        if (m.right().Is(0) && CanCover(user, value)) {
+        if (m.right().Is(0)) {
           // Try to combine the branch with a comparison.
           Node* const eq_user = m.node();
           Node* const eq_value = m.left().node();
@@ -2646,6 +2624,7 @@
         break;
     }
   }
+
   // Branch could not be combined with a compare, emit compare against 0.
   VisitCompareZero(this, user, value, kX64Cmp32, cont);
 }