commit 7f8678ec4d2abec1f540fb441be60604bec86b6e
author Mathieu Chartier <mathieuc@google.com> Fri Aug 30 16:22:28 2019 -0700
committer Mathieu Chartier <mathieuc@google.com> Fri Sep 06 18:40:59 2019 +0000
tree e36b4d32dfc47fcebadf0ee5c7e4d1e3d51412a6
parent 84e5bb990d48263849bab132d80d753495bc7204

Revert^2 "Prevent overflow for AOT hotness counters"

Fixed bug where sbc usage was incorrect. sbc does -1 + carry.

Test: test/run-test --always-clean --runtime-option -Xcheck:jni --64 674-hotness-compiled
Test: test/run-test --always-clean --runtime-option -Xcheck:jni 674-hotness-compiled
Bug: 139883463

This reverts commit 7ab07777b08db86dda2891f3e7ae15df8f25a599.

Change-Id: I6f8ac0320592a94314386b04cdb0c7e0e6da6994

compiler/optimizing/code_generator_arm_vixl.cc

diff --git a/compiler/optimizing/code_generator_arm_vixl.cc b/compiler/optimizing/code_generator_arm_vixl.cc
index b3141bf..02286d8 100644
--- a/compiler/optimizing/code_generator_arm_vixl.cc
+++ b/compiler/optimizing/code_generator_arm_vixl.cc
@@ -2087,8 +2087,12 @@
   if (GetCompilerOptions().CountHotnessInCompiledCode()) {
     UseScratchRegisterScope temps(GetVIXLAssembler());
     vixl32::Register temp = temps.Acquire();
+    static_assert(ArtMethod::MaxCounter() == 0xFFFF, "asm is probably wrong");
+    // Load with sign extend to set the high bits for integer overflow check.
     __ Ldrh(temp, MemOperand(kMethodRegister, ArtMethod::HotnessCountOffset().Int32Value()));
     __ Add(temp, temp, 1);
+    // Subtract one if the counter would overflow.
+    __ Sub(temp, temp, Operand(temp, ShiftType::LSR, 16));
     __ Strh(temp, MemOperand(kMethodRegister, ArtMethod::HotnessCountOffset().Int32Value()));
   }
 
@@ -2497,8 +2501,11 @@
       vixl32::Register temp = temps.Acquire();
       __ Push(vixl32::Register(kMethodRegister));
       GetAssembler()->LoadFromOffset(kLoadWord, kMethodRegister, sp, kArmWordSize);
+      // Load with sign extend to set the high bits for integer overflow check.
       __ Ldrh(temp, MemOperand(kMethodRegister, ArtMethod::HotnessCountOffset().Int32Value()));
       __ Add(temp, temp, 1);
+      // Subtract one if the counter would overflow.
+      __ Sub(temp, temp, Operand(temp, ShiftType::LSR, 16));
       __ Strh(temp, MemOperand(kMethodRegister, ArtMethod::HotnessCountOffset().Int32Value()));
       __ Pop(vixl32::Register(kMethodRegister));
     }