BoundsCheck should be extended to support array_bounds_checks_elimination

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
===================================================================
--- src/x64/lithium-codegen-x64.cc	(revision 11854)
+++ src/x64/lithium-codegen-x64.cc	(working copy)
@@ -3489,30 +3489,63 @@
 
 
 void LCodeGen::DoBoundsCheck(LBoundsCheck* instr) {
-  if (instr->length()->IsRegister()) {
-    Register reg = ToRegister(instr->length());
-    if (FLAG_debug_code) {
-      __ AbortIfNotZeroExtended(reg);
+  int32_t lower_offset = instr->hydrogen()->lower_offset();
+  int32_t upper_offset = instr->hydrogen()->upper_offset();
+  LOperand* length = instr->length();
+  LOperand* index = instr->index();
+  if (instr->index()->IsConstantOperand()) {
+    int32_t c_index = ToInteger32(LConstantOperand::cast(index));
+    int64_t upper_range = (int64_t)c_index + (int64_t)upper_offset;
+    if (c_index < -lower_offset || upper_range > ((int64_t)1 << 32)) {
+      DeoptimizeIf(no_condition, instr->environment());
     }
-    if (instr->index()->IsConstantOperand()) {
-      __ cmpq(reg,
-              Immediate(ToInteger32(LConstantOperand::cast(instr->index()))));
-    } else {
-      Register reg2 = ToRegister(instr->index());
+    if (length->IsRegister()) {
       if (FLAG_debug_code) {
-        __ AbortIfNotZeroExtended(reg2);
+        __ AbortIfNotZeroExtended(ToRegister(length));
       }
-      __ cmpq(reg, reg2);
+      __ cmpl(ToRegister(length), Immediate(c_index + upper_offset));
+    } else {
+      __ cmpq(ToOperand(length), Immediate(c_index + upper_offset));
     }
+    DeoptimizeIf(below_equal, instr->environment());
   } else {
-    if (instr->index()->IsConstantOperand()) {
-      __ cmpq(ToOperand(instr->length()),
-              Immediate(ToInteger32(LConstantOperand::cast(instr->index()))));
+    ASSERT(index->IsRegister());
+    Register reg_index = ToRegister(index);
+    if (FLAG_debug_code) {
+      __ AbortIfNotZeroExtended(reg_index);
+    }
+    if (lower_offset == 0 && upper_offset == 0) {
+      if (length->IsRegister()) {
+        if (FLAG_debug_code) {
+          __ AbortIfNotZeroExtended(ToRegister(length));
+        }
+        __ cmpl(ToRegister(length), ToRegister(index));
+      } else {
+        __ cmpq(ToOperand(length), ToRegister(index));
+      }
+      DeoptimizeIf(below_equal, instr->environment());
     } else {
-      __ cmpq(ToOperand(instr->length()), ToRegister(instr->index()));
+      ASSERT(instr->TempAt(0)->IsRegister());
+      Register temp_length = ToRegister(instr->TempAt(0));
+      if (length->IsRegister()) {
+        if (FLAG_debug_code) {
+          __ AbortIfNotZeroExtended(ToRegister(length));
+        }
+        __ movl(temp_length, ToRegister(length));
+      } else {
+        __ movq(temp_length, ToOperand(length));
+      }
+      __ cmpl(reg_index, Immediate(-lower_offset));
+      DeoptimizeIf(less, instr->environment());
+      __ subl(temp_length, Immediate(upper_offset));
+      __ cmpl(reg_index, temp_length);
+      if (upper_offset >= 0) {
+        DeoptimizeIf(greater_equal, instr->environment());
+      } else {
+        DeoptimizeIf(above_equal, instr->environment());
+      }
     }
   }
-  DeoptimizeIf(below_equal, instr->environment());
 }