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

7 files changed, 44 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