Fixed flooring division by -1 on ARM.

src/ia32/lithium-codegen-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1604 matching lines @@
   // 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) {
     __ sar(dividend, shift);
     return;
   }
 
   // If the divisor is negative, we have to negate and handle edge cases.
-  Label not_kmin_int, done;
   __ neg(dividend);
   if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
     DeoptimizeIf(zero, instr->environment());
   }
-  if (instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
-    // Note that we could emit branch-free code, but that would need one more
-    // register.
-    if (divisor == -1) {
-      DeoptimizeIf(overflow, instr->environment());
-    } else {
-      __ j(no_overflow, &not_kmin_int, Label::kNear);
-      __ mov(dividend, Immediate(kMinInt / divisor));
-      __ jmp(&done, Label::kNear);
-    }
+
+  if (!instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
+    __ sar(dividend, shift);
+    return;
   }
+
+  // Dividing by -1 is basically negation, unless we overflow.
+  if (divisor == -1) {
+    DeoptimizeIf(overflow, instr->environment());
+    return;
+  }
+
+  Label not_kmin_int, done;
+  __ j(no_overflow, &not_kmin_int, Label::kNear);
+  __ mov(dividend, Immediate(kMinInt / divisor));
+  __ jmp(&done, Label::kNear);
   __ bind(&not_kmin_int);
   __ sar(dividend, shift);
   __ bind(&done);
 }
 
 
 void LCodeGen::DoFlooringDivByConstI(LFlooringDivByConstI* instr) {
   Register dividend = ToRegister(instr->dividend());
   int32_t divisor = instr->divisor();
   ASSERT(ToRegister(instr->result()).is(edx));
@@ skipping 4793 matching lines @@
   __ bind(deferred->exit());
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32