Fix overflow check when shifting unboxed mints on 32-bit platforms, except on

runtime/vm/intermediate_language_arm.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_ARM.
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/cpu.h"
@@ skipping 536 matching lines @@
       return VS;
   }
 }
 
 
 static Condition EmitUnboxedMintEqualityOp(FlowGraphCompiler* compiler,
                                            LocationSummary* locs,
                                            Token::Kind kind) {
   ASSERT(Token::IsEqualityOperator(kind));
   PairLocation* left_pair = locs->in(0).AsPairLocation();
-  Register left1 = left_pair->At(0).reg();
-  Register left2 = left_pair->At(1).reg();
+  Register left_lo = left_pair->At(0).reg();
+  Register left_hi = left_pair->At(1).reg();
   PairLocation* right_pair = locs->in(1).AsPairLocation();
-  Register right1 = right_pair->At(0).reg();
-  Register right2 = right_pair->At(1).reg();
+  Register right_lo = right_pair->At(0).reg();
+  Register right_hi = right_pair->At(1).reg();
 
   // Compare lower.
-  __ cmp(left1, Operand(right1));
+  __ cmp(left_lo, Operand(right_lo));
   // Compare upper if lower is equal.
-  __ cmp(left2, Operand(right2), EQ);
+  __ cmp(left_hi, Operand(right_hi), EQ);
   return TokenKindToMintCondition(kind);
 }
 
 
 static Condition EmitUnboxedMintComparisonOp(FlowGraphCompiler* compiler,
                                              LocationSummary* locs,
                                              Token::Kind kind) {
   PairLocation* left_pair = locs->in(0).AsPairLocation();
-  Register left1 = left_pair->At(0).reg();
-  Register left2 = left_pair->At(1).reg();
+  Register left_lo = left_pair->At(0).reg();
+  Register left_hi = left_pair->At(1).reg();
   PairLocation* right_pair = locs->in(1).AsPairLocation();
-  Register right1 = right_pair->At(0).reg();
-  Register right2 = right_pair->At(1).reg();
+  Register right_lo = right_pair->At(0).reg();
+  Register right_hi = right_pair->At(1).reg();
 
   Register out = locs->temp(0).reg();
 
   // 64-bit comparison
   Condition hi_true_cond, hi_false_cond, lo_false_cond;
   switch (kind) {
     case Token::kLT:
     case Token::kLTE:
       hi_true_cond = LT;
       hi_false_cond = GT;
       lo_false_cond = (kind == Token::kLT) ? CS : HI;
       break;
     case Token::kGT:
     case Token::kGTE:
       hi_true_cond = GT;
       hi_false_cond = LT;
       lo_false_cond = (kind == Token::kGT) ? LS : CC;
       break;
     default:
       UNREACHABLE();
       hi_true_cond = hi_false_cond = lo_false_cond = VS;
   }
 
-  Label is_true, is_false, done;
+  Label done;
   // Compare upper halves first.
-  __ cmp(left2, Operand(right2));
+  __ cmp(left_hi, Operand(right_hi));
   __ LoadImmediate(out, 0, hi_false_cond);
   __ LoadImmediate(out, 1, hi_true_cond);
   // If higher words aren't equal, skip comparing lower words.
   __ b(&done, NE);
 
-  __ cmp(left1, Operand(right1));
+  __ cmp(left_lo, Operand(right_lo));
   __ LoadImmediate(out, 1);
   __ LoadImmediate(out, 0, lo_false_cond);
   __ Bind(&done);
 
   return NegateCondition(lo_false_cond);
 }
 
 
 static Condition TokenKindToDoubleCondition(Token::Kind kind) {
   switch (kind) {
@@ skipping 200 matching lines @@
   const intptr_t kNumInputs = 2;
   const intptr_t kNumTemps = 0;
   if (operation_cid() == kMintCid) {
     const intptr_t kNumTemps = 1;
     LocationSummary* locs = new(isolate) LocationSummary(
         isolate, kNumInputs, kNumTemps, LocationSummary::kNoCall);
     locs->set_in(0, Location::Pair(Location::RequiresRegister(),
                                    Location::RequiresRegister()));
     locs->set_in(1, Location::Pair(Location::RequiresRegister(),
                                    Location::RequiresRegister()));
-    locs->set_temp(0, Location::RequiresRegister());
+    locs->set_temp(0, Location::RequiresRegister());  // TODO(regis): Improve.
     locs->set_out(0, Location::RequiresRegister());
     return locs;
   }
   if (operation_cid() == kDoubleCid) {
     LocationSummary* summary = new(isolate) LocationSummary(
         isolate, kNumInputs, kNumTemps, LocationSummary::kNoCall);
     summary->set_in(0, Location::RequiresFpuRegister());
     summary->set_in(1, Location::RequiresFpuRegister());
     summary->set_out(0, Location::RequiresRegister());
     return summary;
@@ skipping 53 matching lines @@
 
 
 void RelationalOpInstr::EmitBranchCode(FlowGraphCompiler* compiler,
                                        BranchInstr* branch) {
   BranchLabels labels = compiler->CreateBranchLabels(branch);
   Condition true_condition = EmitComparisonCode(compiler, labels);
 
   if (operation_cid() == kSmiCid) {
     EmitBranchOnCondition(compiler, true_condition, labels);
   } else if (operation_cid() == kMintCid) {
-    const Register result = locs()->temp(0).reg();
+    const Register result = locs()->temp(0).reg();  // TODO(regis): Improve.
     __ CompareImmediate(result, 1);
     __ b(labels.true_label, EQ);
     __ b(labels.false_label, NE);
   } else if (operation_cid() == kDoubleCid) {
     Label* nan_result = (true_condition == NE) ?
         labels.true_label : labels.false_label;
     __ b(nan_result, VS);
     EmitBranchOnCondition(compiler, true_condition, labels);
   }
 }
@@ skipping 2958 matching lines @@
     __ StoreToOffset(kWord,
                      temp,
                      out,
                      Mint::value_offset() - kHeapObjectTag + kWordSize);
     __ Bind(&done);
   }
 }
 
 
 LocationSummary* BoxInt64Instr::MakeLocationSummary(Isolate* isolate,
-                                                      bool opt) const {
+                                                    bool opt) const {
   const intptr_t kNumInputs = 1;
   const intptr_t kNumTemps = ValueFitsSmi() ? 0 : 1;
   LocationSummary* summary = new(isolate) LocationSummary(
       isolate,
       kNumInputs,
       kNumTemps,
       ValueFitsSmi() ? LocationSummary::kNoCall
                      : LocationSummary::kCallOnSlowPath);
   summary->set_in(0, Location::Pair(Location::RequiresRegister(),
                                     Location::RequiresRegister()));
@@ skipping 2422 matching lines @@
           if (shift == 32) {
             __ mov(out_hi, Operand(left_lo));
           } else {
             __ Lsl(out_hi, left_lo, Operand(shift - 32));
           }
           __ mov(out_lo, Operand(0));
         }
         // Check for overflow.
         if (can_overflow()) {
           // Compare high word from input with shifted high word from output.
-          if (shift > 31) {
-            __ cmp(left_hi, Operand(out_hi));
+          // If shift > 32, also compare low word from input with high word from
+          // output shifted back shift - 32.
+          if (shift > 32) {
+            __ cmp(left_lo, Operand(out_hi, ASR, shift - 32));
+            __ cmp(left_hi, Operand(out_hi, ASR, 31), EQ);
+          } else if (shift == 32) {
+            __ cmp(left_hi, Operand(out_hi, ASR, 31));
           } else {
             __ cmp(left_hi, Operand(out_hi, ASR, shift));
           }
           // Overflow if they aren't equal.
           __ b(deopt, NE);
         }
         break;
       }
       default:
         UNREACHABLE();
     }
   } else {
     // Code for a variable shift amount.
     Register shift = locs()->in(1).reg();
 
     // Untag shift count.
     __ SmiUntag(shift);
 
     // Deopt if shift is larger than 63 or less than 0.
     if (has_shift_count_check()) {
       __ CompareImmediate(shift, kMintShiftCountLimit);
       __ b(deopt, HI);
     }
 
-    __ mov(out_lo, Operand(left_lo));
-    __ mov(out_hi, Operand(left_hi));
-
     switch (op_kind()) {
       case Token::kSHR: {
-        __ cmp(shift, Operand(32));
-
-        __ mov(out_lo, Operand(out_hi), HI);
-        __ Asr(out_hi, out_hi, Operand(31), HI);
-        __ sub(shift, shift, Operand(32), HI);
-
-        __ rsb(IP, shift, Operand(32));
-        __ mov(IP, Operand(out_hi, LSL, IP));
-        __ orr(out_lo, IP, Operand(out_lo, LSR, shift));
-        __ Asr(out_hi, out_hi, shift);
+        __ rsbs(IP, shift, Operand(32));
+        __ sub(IP, shift, Operand(32), MI);
+        __ mov(out_lo, Operand(left_hi, ASR, IP), MI);
+        __ mov(out_lo, Operand(left_lo, LSR, shift), PL);
+        __ orr(out_lo, out_lo, Operand(left_hi, LSL, IP), PL);
+        __ mov(out_hi, Operand(left_hi, ASR, shift));
         break;
       }
       case Token::kSHL: {
         __ rsbs(IP, shift, Operand(32));
         __ sub(IP, shift, Operand(32), MI);
-        __ mov(out_hi, Operand(out_lo, LSL, IP), MI);
-        __ mov(out_hi, Operand(out_hi, LSL, shift), PL);
-        __ orr(out_hi, out_hi, Operand(out_lo, LSR, IP), PL);
-        __ mov(out_lo, Operand(out_lo, LSL, shift));
+        __ mov(out_hi, Operand(left_lo, LSL, IP), MI);
+        __ mov(out_hi, Operand(left_hi, LSL, shift), PL);
+        __ orr(out_hi, out_hi, Operand(left_lo, LSR, IP), PL);
+        __ mov(out_lo, Operand(left_lo, LSL, shift));
 
         // Check for overflow.
         if (can_overflow()) {
+          // If shift > 32, compare low word from input with high word from
+          // output shifted back shift - 32.
+          __ mov(IP, Operand(out_hi, ASR, IP), MI);
+          __ mov(IP, Operand(left_lo), PL);  // No test if shift <= 32.
+          __ cmp(left_lo, Operand(IP));
           // Compare high word from input with shifted high word from output.
-          __ cmp(left_hi, Operand(out_hi, ASR, shift));
+          __ cmp(left_hi, Operand(out_hi, ASR, shift), EQ);
           // Overflow if they aren't equal.
           __ b(deopt, NE);
         }
         break;
       }
       default:
         UNREACHABLE();
     }
   }
 
@@ skipping 507 matching lines @@
   compiler->GenerateCall(token_pos(), &label, stub_kind_, locs());
 #if defined(DEBUG)
   __ LoadImmediate(R4, kInvalidObjectPointer);
   __ LoadImmediate(R5, kInvalidObjectPointer);
 #endif
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM