Fix FlooringDivByPowerOf2I on ARM/ARM64

src/arm64/lithium-codegen-arm64.cc

 // Copyright 2013 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 "v8.h"
 
 #include "arm64/lithium-codegen-arm64.h"
 #include "arm64/lithium-gap-resolver-arm64.h"
 #include "code-stubs.h"
 #include "stub-cache.h"
@@ skipping 3852 matching lines @@
   __ Fccmp(input, input, NoFlag, eq);
   DeoptimizeIf(ne, instr->environment());
 }
 
 
 void LCodeGen::DoFlooringDivByPowerOf2I(LFlooringDivByPowerOf2I* instr) {
   Register dividend = ToRegister32(instr->dividend());
   Register result = ToRegister32(instr->result());
   int32_t divisor = instr->divisor();
 
+  // If the divisor is 1, return the dividend.
+  if (divisor == 1) {
+    __ Mov(result, dividend, kDiscardForSameWReg);
+    return;
+  }
+
   // If the divisor is positive, things are easy: There can be no deopts and we
   // can simply do an arithmetic right shift.
-  if (divisor == 1) return;
   int32_t shift = WhichPowerOf2Abs(divisor);
   if (divisor > 1) {
     __ Mov(result, Operand(dividend, ASR, shift));
     return;
   }
 
   // If the divisor is negative, we have to negate and handle edge cases.
   __ Negs(result, dividend);
   if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
     DeoptimizeIf(eq, instr->environment());
   }
 
   // If the negation could not overflow, simply shifting is OK.
   if (!instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
     __ Mov(result, Operand(dividend, ASR, shift));
     return;
   }
 
   // Dividing by -1 is basically negation, unless we overflow.
   if (divisor == -1) {
     DeoptimizeIf(vs, instr->environment());
     return;
   }
 
-  // Using a conditional data processing instruction would need 1 more register.
-  Label not_kmin_int, done;
-  __ B(vc, &not_kmin_int);
-  __ Mov(result, kMinInt / divisor);
-  __ B(&done);
-  __ bind(&not_kmin_int);
-  __ Mov(result, Operand(dividend, ASR, shift));
-  __ bind(&done);
+  __ Asr(result, dividend, shift);
+  __ Csel(result, result, kMinInt / divisor, vc);
 }
 
 
 void LCodeGen::DoFlooringDivByConstI(LFlooringDivByConstI* instr) {
   Register dividend = ToRegister32(instr->dividend());
   int32_t divisor = instr->divisor();
   Register result = ToRegister32(instr->result());
   ASSERT(!AreAliased(dividend, result));
 
   if (divisor == 0) {
@@ skipping 2083 matching lines @@
   __ Ldr(result, FieldMemOperand(object, JSObject::kPropertiesOffset));
   // Index is equal to negated out of object property index plus 1.
   __ Sub(result, result, Operand::UntagSmiAndScale(index, kPointerSizeLog2));
   __ Ldr(result, FieldMemOperand(result,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ Bind(deferred->exit());
   __ Bind(&done);
 }
 
 } }  // namespace v8::internal