[arm64] Emit CBZ for deoptimisations.

src/compiler/arm64/instruction-selector-arm64.cc

Index: src/compiler/arm64/instruction-selector-arm64.cc
diff --git a/src/compiler/arm64/instruction-selector-arm64.cc b/src/compiler/arm64/instruction-selector-arm64.cc
index da27be8626acbc43b653c36b541388a76e5bc5f7..be56d5cc81c37bffafeb04150b75e3636e41cae5 100644
--- a/src/compiler/arm64/instruction-selector-arm64.cc
+++ b/src/compiler/arm64/instruction-selector-arm64.cc
@@ -2152,6 +2152,20 @@ FlagsCondition MapForCbz(FlagsCondition cond) {
   }
 }
 
+void EmitBranchOrDeoptimize(InstructionSelector* selector,
+                            InstructionCode opcode, InstructionOperand value,
+                            FlagsContinuation* cont) {
+  Arm64OperandGenerator g(selector);
+  if (cont->IsBranch()) {
+    selector->Emit(cont->Encode(opcode), g.NoOutput(), value,
+                   g.Label(cont->true_block()), g.Label(cont->false_block()));
+  } else {
+    DCHECK(cont->IsDeoptimize());
+    selector->EmitDeoptimize(cont->Encode(opcode), g.NoOutput(), value,
+                             cont->reason(), cont->frame_state());
+  }
+}
+
 // Try to emit TBZ, TBNZ, CBZ or CBNZ for certain comparisons of {node}
 // against zero, depending on the condition.
 bool TryEmitCbzOrTbz(InstructionSelector* selector, Node* node, Node* user,
@@ -2160,12 +2174,16 @@ bool TryEmitCbzOrTbz(InstructionSelector* selector, Node* node, Node* user,
   USE(m_user);
   DCHECK(m_user.right().Is(0) || m_user.left().Is(0));
 
-  // Only handle branches.
-  if (!cont->IsBranch()) return false;
+  // Only handle branches and deoptimisations.
+  if (!cont->IsBranch() && !cont->IsDeoptimize()) return false;
 
   switch (cond) {
     case kSignedLessThan:
     case kSignedGreaterThanOrEqual: {
+      // We don't generate TBZ/TBNZ for deoptimisations, as they have a
+      // shorter range than conditional branches and generating them for
+      // deoptimisations results in more veneers.
+      if (cont->IsDeoptimize()) return false;
       Arm64OperandGenerator g(selector);
       cont->Overwrite(MapForTbz(cond));
       Int32Matcher m(node);
@@ -2192,9 +2210,8 @@ bool TryEmitCbzOrTbz(InstructionSelector* selector, Node* node, Node* user,
     case kUnsignedGreaterThan: {
       Arm64OperandGenerator g(selector);
       cont->Overwrite(MapForCbz(cond));
-      selector->Emit(cont->Encode(kArm64CompareAndBranch32), g.NoOutput(),
-                     g.UseRegister(node), g.Label(cont->true_block()),
-                     g.Label(cont->false_block()));
+      EmitBranchOrDeoptimize(selector, kArm64CompareAndBranch32,
+                             g.UseRegister(node), cont);
       return true;
     }
     default:
@@ -2380,10 +2397,10 @@ void VisitWordCompareZero(InstructionSelector* selector, Node* user,
                                     kLogical64Imm);
           }
           // Merge the Word64Equal(x, 0) comparison into a cbz instruction.
-          if (cont->IsBranch()) {
-            selector->Emit(cont->Encode(kArm64CompareAndBranch), g.NoOutput(),
-                           g.UseRegister(left), g.Label(cont->true_block()),
-                           g.Label(cont->false_block()));
+          if (cont->IsBranch() || cont->IsDeoptimize()) {
+            EmitBranchOrDeoptimize(selector,
+                                   cont->Encode(kArm64CompareAndBranch),
+                                   g.UseRegister(left), cont);
             return;
           }
         }