Update HInstruction::NeedsCurrentMethod.

HLoadString and HLoadClass when sharpened may not need it
anymore. Instead just rely on the HCurrentMethod being the
SSA dependency of those instructions.

Also save storing the current method in the stack if the
graph actually doesn't need it.

test: m test-art-host test-art-target
Change-Id: I235d8275230637cbbd38fc0d2f9b822f6d2a9c1e

10 files changed, 79 insertions, 14 deletions

diff --git a/compiler/optimizing/code_generator_arm.cc b/compiler/optimizing/code_generator_arm.cc
index 9870876879..77d6f23fff 100644
--- a/compiler/optimizing/code_generator_arm.cc
+++ b/compiler/optimizing/code_generator_arm.cc
@@ -1129,7 +1129,13 @@ void CodeGeneratorARM::GenerateFrameEntry() {
   int adjust = GetFrameSize() - FrameEntrySpillSize();
   __ AddConstant(SP, -adjust);
   __ cfi().AdjustCFAOffset(adjust);
-  __ StoreToOffset(kStoreWord, kMethodRegisterArgument, SP, 0);
+
+  // Save the current method if we need it. Note that we do not
+  // do this in HCurrentMethod, as the instruction might have been removed
+  // in the SSA graph.
+  if (RequiresCurrentMethod()) {
+    __ StoreToOffset(kStoreWord, kMethodRegisterArgument, SP, 0);
+  }
 }
 
 void CodeGeneratorARM::GenerateFrameExit() {
diff --git a/compiler/optimizing/code_generator_arm64.cc b/compiler/optimizing/code_generator_arm64.cc
index 969d653f97..b1e4f5c763 100644
--- a/compiler/optimizing/code_generator_arm64.cc
+++ b/compiler/optimizing/code_generator_arm64.cc
@@ -1046,7 +1046,13 @@ void CodeGeneratorARM64::GenerateFrameEntry() {
     //      ...                       : other preserved fp registers.
     //      ...                       : reserved frame space.
     //      sp[0]                     : current method.
-    __ Str(kArtMethodRegister, MemOperand(sp, -frame_size, PreIndex));
+
+    // Save the current method if we need it. Note that we do not
+    // do this in HCurrentMethod, as the instruction might have been removed
+    // in the SSA graph.
+    if (RequiresCurrentMethod()) {
+      __ Str(kArtMethodRegister, MemOperand(sp, -frame_size, PreIndex));
+    }
     GetAssembler()->cfi().AdjustCFAOffset(frame_size);
     GetAssembler()->SpillRegisters(GetFramePreservedCoreRegisters(),
         frame_size - GetCoreSpillSize());
diff --git a/compiler/optimizing/code_generator_mips.cc b/compiler/optimizing/code_generator_mips.cc
index 990bbcc85b..bc8bb480ec 100644
--- a/compiler/optimizing/code_generator_mips.cc
+++ b/compiler/optimizing/code_generator_mips.cc
@@ -743,9 +743,12 @@ void CodeGeneratorMIPS::GenerateFrameEntry() {
     // TODO: __ cfi().RelOffset(DWARFReg(reg), ofs);
   }
 
-  // Store the current method pointer.
-  // TODO: can we not do this if RequiresCurrentMethod() returns false?
-  __ StoreToOffset(kStoreWord, kMethodRegisterArgument, SP, kCurrentMethodStackOffset);
+  // Save the current method if we need it. Note that we do not
+  // do this in HCurrentMethod, as the instruction might have been removed
+  // in the SSA graph.
+  if (RequiresCurrentMethod()) {
+    __ StoreToOffset(kStoreWord, kMethodRegisterArgument, SP, kCurrentMethodStackOffset);
+  }
 }
 
 void CodeGeneratorMIPS::GenerateFrameExit() {
diff --git a/compiler/optimizing/code_generator_mips64.cc b/compiler/optimizing/code_generator_mips64.cc
index 02576bda67..010bf24232 100644
--- a/compiler/optimizing/code_generator_mips64.cc
+++ b/compiler/optimizing/code_generator_mips64.cc
@@ -556,9 +556,14 @@ void CodeGeneratorMIPS64::GenerateFrameEntry() {
 
   __ IncreaseFrameSize(GetFrameSize() - FrameEntrySpillSize());
 
-  static_assert(IsInt<16>(kCurrentMethodStackOffset),
-                "kCurrentMethodStackOffset must fit into int16_t");
-  __ Sd(kMethodRegisterArgument, SP, kCurrentMethodStackOffset);
+  // Save the current method if we need it. Note that we do not
+  // do this in HCurrentMethod, as the instruction might have been removed
+  // in the SSA graph.
+  if (RequiresCurrentMethod()) {
+    static_assert(IsInt<16>(kCurrentMethodStackOffset),
+                  "kCurrentMethodStackOffset must fit into int16_t");
+    __ Sd(kMethodRegisterArgument, SP, kCurrentMethodStackOffset);
+  }
 }
 
 void CodeGeneratorMIPS64::GenerateFrameExit() {
diff --git a/compiler/optimizing/code_generator_x86.cc b/compiler/optimizing/code_generator_x86.cc
index 0b23599665..960f01ce9d 100644
--- a/compiler/optimizing/code_generator_x86.cc
+++ b/compiler/optimizing/code_generator_x86.cc
@@ -898,7 +898,12 @@ void CodeGeneratorX86::GenerateFrameEntry() {
   int adjust = GetFrameSize() - FrameEntrySpillSize();
   __ subl(ESP, Immediate(adjust));
   __ cfi().AdjustCFAOffset(adjust);
-  __ movl(Address(ESP, kCurrentMethodStackOffset), kMethodRegisterArgument);
+  // Save the current method if we need it. Note that we do not
+  // do this in HCurrentMethod, as the instruction might have been removed
+  // in the SSA graph.
+  if (RequiresCurrentMethod()) {
+    __ movl(Address(ESP, kCurrentMethodStackOffset), kMethodRegisterArgument);
+  }
 }
 
 void CodeGeneratorX86::GenerateFrameExit() {
diff --git a/compiler/optimizing/code_generator_x86_64.cc b/compiler/optimizing/code_generator_x86_64.cc
index 28638d721d..665d028338 100644
--- a/compiler/optimizing/code_generator_x86_64.cc
+++ b/compiler/optimizing/code_generator_x86_64.cc
@@ -1140,8 +1140,13 @@ void CodeGeneratorX86_64::GenerateFrameEntry() {
     }
   }
 
-  __ movq(Address(CpuRegister(RSP), kCurrentMethodStackOffset),
-          CpuRegister(kMethodRegisterArgument));
+  // Save the current method if we need it. Note that we do not
+  // do this in HCurrentMethod, as the instruction might have been removed
+  // in the SSA graph.
+  if (RequiresCurrentMethod()) {
+    __ movq(Address(CpuRegister(RSP), kCurrentMethodStackOffset),
+            CpuRegister(kMethodRegisterArgument));
+  }
 }
 
 void CodeGeneratorX86_64::GenerateFrameExit() {
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 348f99d6df..426c4f1fa0 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -2093,10 +2093,10 @@ class HInstruction : public ArenaObject<kArenaAllocInstruction> {
   // to the current method. Such instructions are:
   // (1): Instructions that require an environment, as calling the runtime requires
   //      to walk the stack and have the current method stored at a specific stack address.
-  // (2): Object literals like classes and strings, that are loaded from the dex cache
-  //      fields of the current method.
+  // (2): HCurrentMethod, potentially used by HInvokeStaticOrDirect, HLoadString, or HLoadClass
+  //      to access the dex cache.
   bool NeedsCurrentMethod() const {
-    return NeedsEnvironment() || IsLoadClass() || IsLoadString();
+    return NeedsEnvironment() || IsCurrentMethod();
   }
 
   // Returns whether the code generation of the instruction will require to have access
diff --git a/test/619-checker-current-method/expected.txt b/test/619-checker-current-method/expected.txt
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/test/619-checker-current-method/expected.txt
diff --git a/test/619-checker-current-method/info.txt b/test/619-checker-current-method/info.txt
new file mode 100644
index 0000000000..75f5213975
--- /dev/null
+++ b/test/619-checker-current-method/info.txt
@@ -0,0 +1,2 @@
+Checks that we don't store the current method when the compiled
+code does not need it.
diff --git a/test/619-checker-current-method/src/Main.java b/test/619-checker-current-method/src/Main.java
new file mode 100644
index 0000000000..d829370d74
--- /dev/null
+++ b/test/619-checker-current-method/src/Main.java
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+public class Main {
+
+  // Check that there is no instruction storing to stack.
+  /// CHECK-START-X86: int Main.foo(int, int, int, int, int, int) disassembly (after)
+  /// CHECK-NOT:  mov [{{\w+}}], {{\w+}}
+
+  // Use enough parameters to ensure we'll need a frame.
+  public static int foo(int a, int b, int c, int d, int e, int f) {
+    return a + b + c + d + e + f;
+  }
+
+  public static void main(String[] args) {
+    if (foo(1, 2, 3, 4, 5, 6) != 21) {
+      throw new Error("Expected 21");
+    }
+  }
+}