Fixed flooring division by a power of 2, once again...

src/x64/lithium-codegen-x64.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 "src/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/x64/lithium-codegen-x64.h"
 #include "src/code-stubs.h"
@@ skipping 1116 matching lines @@
     __ sarl(dividend, Immediate(shift));
     return;
   }
 
   // If the divisor is negative, we have to negate and handle edge cases.
   __ negl(dividend);
   if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
     DeoptimizeIf(zero, instr->environment());
   }
 
+  // Dividing by -1 is basically negation, unless we overflow.
+  if (divisor == -1) {
+    if (instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
+      DeoptimizeIf(overflow, instr->environment());
+    }
+    return;
+  }
+
   // If the negation could not overflow, simply shifting is OK.
   if (!instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
     __ sarl(dividend, Immediate(shift));
     return;
   }
 
-  // Note that we could emit branch-free code, but that would need one more
-  // register.
-  if (divisor == -1) {
-    DeoptimizeIf(overflow, instr->environment());
-    return;
-  }
-
   Label not_kmin_int, done;
   __ j(no_overflow, &not_kmin_int, Label::kNear);
   __ movl(dividend, Immediate(kMinInt / divisor));
   __ jmp(&done, Label::kNear);
   __ bind(&not_kmin_int);
   __ sarl(dividend, Immediate(shift));
   __ bind(&done);
 }
 
 
@@ skipping 4577 matching lines @@
   CallRuntime(Runtime::kHiddenPushBlockContext, 2, instr);
   RecordSafepoint(Safepoint::kNoLazyDeopt);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64