ART: Fix read-out-of-bounds in the compiler

In case of a wide dalvik register, asking for the constant value
can lead to a read out of bounds.

Bug: 17302671

(cherry picked from commit ade731854d18839823e57fb2d3d67238c5467d15)

Change-Id: Ie1849cd67cc418c97cbd7a8524f027f9b66e4c96

2 files changed, 13 insertions, 4 deletions

diff --git a/compiler/dex/mir_graph.h b/compiler/dex/mir_graph.h
index ef43ea2..078970d 100644
--- a/compiler/dex/mir_graph.h
+++ b/compiler/dex/mir_graph.h
@@ -760,6 +760,8 @@ class MIRGraph {
 
   int64_t ConstantValueWide(RegLocation loc) const {
     DCHECK(IsConst(loc));
+    DCHECK(!loc.high_word);  // Do not allow asking for the high partner.
+    DCHECK_LT(loc.orig_sreg + 1, GetNumSSARegs());
     return (static_cast<int64_t>(constant_values_[loc.orig_sreg + 1]) << 32) |
         Low32Bits(static_cast<int64_t>(constant_values_[loc.orig_sreg]));
   }
diff --git a/compiler/dex/quick/codegen_util.cc b/compiler/dex/quick/codegen_util.cc
index 08e1c1a..6d8f288 100644
--- a/compiler/dex/quick/codegen_util.cc
+++ b/compiler/dex/quick/codegen_util.cc
@@ -57,16 +57,23 @@ bool Mir2Lir::IsInexpensiveConstant(RegLocation rl_src) {
   bool res = false;
   if (rl_src.is_const) {
     if (rl_src.wide) {
+      // For wide registers, check whether we're the high partner. In that case we need to switch
+      // to the lower one for the correct value.
+      if (rl_src.high_word) {
+        rl_src.high_word = false;
+        rl_src.s_reg_low--;
+        rl_src.orig_sreg--;
+      }
       if (rl_src.fp) {
-         res = InexpensiveConstantDouble(mir_graph_->ConstantValueWide(rl_src));
+        res = InexpensiveConstantDouble(mir_graph_->ConstantValueWide(rl_src));
       } else {
-         res = InexpensiveConstantLong(mir_graph_->ConstantValueWide(rl_src));
+        res = InexpensiveConstantLong(mir_graph_->ConstantValueWide(rl_src));
       }
     } else {
       if (rl_src.fp) {
-         res = InexpensiveConstantFloat(mir_graph_->ConstantValue(rl_src));
+        res = InexpensiveConstantFloat(mir_graph_->ConstantValue(rl_src));
       } else {
-         res = InexpensiveConstantInt(mir_graph_->ConstantValue(rl_src));
+        res = InexpensiveConstantInt(mir_graph_->ConstantValue(rl_src));
       }
     }
   }