ART: Change GenPCUseDefEncoding(), turn on Load Hoisting for ARM64

This defines the PC resource mask as empty, as the PC is not
accessible on ARM64.

Unify code paths with x86 in LoadStoreElimination and LoadHoisting.

Change-Id: Iea8b9e666f306c7a6ff52b6c5bf7e05b35346b2c

6 files changed, 33 insertions, 29 deletions

diff --git a/compiler/dex/frontend.cc b/compiler/dex/frontend.cc
index 711743d69b..d097500a77 100644
--- a/compiler/dex/frontend.cc
+++ b/compiler/dex/frontend.cc
@@ -96,7 +96,6 @@ static constexpr uint32_t kDisabledOptimizationsPerISA[] = {
     ~0U,
     // 2 = kArm64.     TODO(Arm64): enable optimizations once backend is mature enough.
     (1 << kLoadStoreElimination) |
-    (1 << kLoadHoisting) |
     0,
     // 3 = kThumb2.
     0,
diff --git a/compiler/dex/quick/arm64/target_arm64.cc b/compiler/dex/quick/arm64/target_arm64.cc
index ef9dbddbde..be3cd8e142 100644
--- a/compiler/dex/quick/arm64/target_arm64.cc
+++ b/compiler/dex/quick/arm64/target_arm64.cc
@@ -158,7 +158,6 @@ ResourceMask Arm64Mir2Lir::GetRegMaskCommon(const RegStorage& reg) const {
 }
 
 ResourceMask Arm64Mir2Lir::GetPCUseDefEncoding() const {
-  LOG(FATAL) << "Unexpected call to GetPCUseDefEncoding for Arm64";
   return kEncodeNone;
 }
 
diff --git a/compiler/dex/quick/local_optimizations.cc b/compiler/dex/quick/local_optimizations.cc
index b97ff2a447..289315747a 100644
--- a/compiler/dex/quick/local_optimizations.cc
+++ b/compiler/dex/quick/local_optimizations.cc
@@ -121,20 +121,22 @@ void Mir2Lir::ApplyLoadStoreElimination(LIR* head_lir, LIR* tail_lir) {
     }
 
     ResourceMask stop_def_reg_mask = this_lir->u.m.def_mask->Without(kEncodeMem);
-    ResourceMask stop_use_reg_mask;
-    if (cu_->instruction_set == kX86 || cu_->instruction_set == kX86_64) {
+
+    /*
+     * Add pc to the resource mask to prevent this instruction
+     * from sinking past branch instructions. Also take out the memory
+     * region bits since stop_mask is used to check data/control
+     * dependencies.
+     *
+     * Note: on x86(-64) and Arm64 we use the IsBranch bit, as the PC is not exposed.
+     */
+    ResourceMask pc_encoding = GetPCUseDefEncoding();
+    if (pc_encoding == kEncodeNone) {
       // TODO: Stop the abuse of kIsBranch as a bit specification for ResourceMask.
-      stop_use_reg_mask = ResourceMask::Bit(kIsBranch).Union(*this_lir->u.m.use_mask).Without(
-          kEncodeMem);
-    } else {
-      /*
-       * Add pc to the resource mask to prevent this instruction
-       * from sinking past branch instructions. Also take out the memory
-       * region bits since stop_mask is used to check data/control
-       * dependencies.
-       */
-      stop_use_reg_mask = GetPCUseDefEncoding().Union(*this_lir->u.m.use_mask).Without(kEncodeMem);
+      pc_encoding = ResourceMask::Bit(kIsBranch);
     }
+    ResourceMask  stop_use_reg_mask = pc_encoding.Union(*this_lir->u.m.use_mask).
+        Without(kEncodeMem);
 
     for (check_lir = NEXT_LIR(this_lir); check_lir != tail_lir; check_lir = NEXT_LIR(check_lir)) {
       /*
@@ -310,16 +312,17 @@ void Mir2Lir::ApplyLoadHoisting(LIR* head_lir, LIR* tail_lir) {
 
     ResourceMask stop_use_all_mask = *this_lir->u.m.use_mask;
 
-    if (cu_->instruction_set != kX86 && cu_->instruction_set != kX86_64) {
-      /*
-       * Branches for null/range checks are marked with the true resource
-       * bits, and loads to Dalvik registers, constant pools, and non-alias
-       * locations are safe to be hoisted. So only mark the heap references
-       * conservatively here.
-       */
-      if (stop_use_all_mask.HasBit(ResourceMask::kHeapRef)) {
-        stop_use_all_mask.SetBits(GetPCUseDefEncoding());
-      }
+    /*
+     * Branches for null/range checks are marked with the true resource
+     * bits, and loads to Dalvik registers, constant pools, and non-alias
+     * locations are safe to be hoisted. So only mark the heap references
+     * conservatively here.
+     *
+     * Note: on x86(-64) and Arm64 this will add kEncodeNone.
+     * TODO: Sanity check. LoadStoreElimination uses kBranchBit to fake a PC.
+     */
+    if (stop_use_all_mask.HasBit(ResourceMask::kHeapRef)) {
+      stop_use_all_mask.SetBits(GetPCUseDefEncoding());
     }
 
     /* Similar as above, but just check for pure register dependency */
diff --git a/compiler/dex/quick/mir_to_lir.h b/compiler/dex/quick/mir_to_lir.h
index 87509b636c..d1e83c2230 100644
--- a/compiler/dex/quick/mir_to_lir.h
+++ b/compiler/dex/quick/mir_to_lir.h
@@ -1263,6 +1263,9 @@ class Mir2Lir : public Backend {
     virtual const char* GetTargetInstFmt(int opcode) = 0;
     virtual const char* GetTargetInstName(int opcode) = 0;
     virtual std::string BuildInsnString(const char* fmt, LIR* lir, unsigned char* base_addr) = 0;
+
+    // Note: This may return kEncodeNone on architectures that do not expose a PC. The caller must
+    //       take care of this.
     virtual ResourceMask GetPCUseDefEncoding() const = 0;
     virtual uint64_t GetTargetInstFlags(int opcode) = 0;
     virtual size_t GetInsnSize(LIR* lir) = 0;
diff --git a/compiler/dex/quick/resource_mask.h b/compiler/dex/quick/resource_mask.h
index 12ce98adc4..436cdb5440 100644
--- a/compiler/dex/quick/resource_mask.h
+++ b/compiler/dex/quick/resource_mask.h
@@ -63,6 +63,11 @@ class ResourceMask {
   ResourceMask(const ResourceMask& other) = default;
   ResourceMask& operator=(const ResourceMask& other) = default;
 
+  // Comparable by content.
+  bool operator==(const ResourceMask& other) {
+    return masks_[0] == other.masks_[0] && masks_[1] == other.masks_[1];
+  }
+
   static constexpr ResourceMask RawMask(uint64_t mask1, uint64_t mask2) {
     return ResourceMask(mask1, mask2);
   }
diff --git a/compiler/dex/quick/x86/target_x86.cc b/compiler/dex/quick/x86/target_x86.cc
index 4310525a5d..0083128501 100755
--- a/compiler/dex/quick/x86/target_x86.cc
+++ b/compiler/dex/quick/x86/target_x86.cc
@@ -246,11 +246,6 @@ ResourceMask X86Mir2Lir::GetRegMaskCommon(const RegStorage& reg) const {
 }
 
 ResourceMask X86Mir2Lir::GetPCUseDefEncoding() const {
-  /*
-   * FIXME: might make sense to use a virtual resource encoding bit for pc.  Might be
-   * able to clean up some of the x86/Arm_Mips differences
-   */
-  LOG(FATAL) << "Unexpected call to GetPCUseDefEncoding for x86";
   return kEncodeNone;
 }