src/code-generation-scopes-vixl.h - platform/external/vixl - Gitiles

 // Copyright 2016, VIXL authors
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are met:
 //
 //   * Redistributions of source code must retain the above copyright notice,
 //     this list of conditions and the following disclaimer.
 //   * Redistributions in binary form must reproduce the above copyright notice,
 //     this list of conditions and the following disclaimer in the documentation
 //     and/or other materials provided with the distribution.
 //   * Neither the name of ARM Limited nor the names of its contributors may be
 //     used to endorse or promote products derived from this software without
 //     specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS CONTRIBUTORS "AS IS" AND
 // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 // WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


 #ifndef VIXL_CODE_GENERATION_SCOPES_H_
 #define VIXL_CODE_GENERATION_SCOPES_H_


 #include "assembler-base-vixl.h"
 #include "macro-assembler-interface.h"


 namespace vixl {

 // This scope will:
 // - Allow code emission from the specified `Assembler`.
 // - Optionally reserve space in the `CodeBuffer` (if it is managed by VIXL).
 // - Optionally, on destruction, check the size of the generated code.
 //   (The size can be either exact or a maximum size.)
 class CodeBufferCheckScope {
  public:
   // Tell whether or not the scope needs to ensure the associated CodeBuffer
   // has enough space for the requested size.
   enum BufferSpacePolicy {
     kReserveBufferSpace,
     kDontReserveBufferSpace,

     // Deprecated, but kept for backward compatibility.
     kCheck = kReserveBufferSpace,
     kNoCheck = kDontReserveBufferSpace
   };

   // Tell whether or not the scope should assert the amount of code emitted
   // within the scope is consistent with the requested amount.
   enum SizePolicy {
     kNoAssert,    // Do not check the size of the code emitted.
     kExactSize,   // The code emitted must be exactly size bytes.
     kMaximumSize  // The code emitted must be at most size bytes.
   };

   // This constructor implicitly calls `Open` to initialise the scope
   // (`assembler` must not be `NULL`), so it is ready to use immediately after
   // it has been constructed.
   CodeBufferCheckScope(internal::AssemblerBase* assembler,
                        size_t size,
                        BufferSpacePolicy check_policy = kReserveBufferSpace,
                        SizePolicy size_policy = kMaximumSize)
       : assembler_(NULL), initialised_(false) {
     Open(assembler, size, check_policy, size_policy);
   }

   // This constructor does not implicitly initialise the scope. Instead, the
   // user is required to explicitly call the `Open` function before using the
   // scope.
   CodeBufferCheckScope() : assembler_(NULL), initialised_(false) {
     // Nothing to do.
   }

   virtual ~CodeBufferCheckScope() { Close(); }

   // This function performs the actual initialisation work.
   void Open(internal::AssemblerBase* assembler,
             size_t size,
             BufferSpacePolicy check_policy = kReserveBufferSpace,
             SizePolicy size_policy = kMaximumSize) {
     VIXL_ASSERT(!initialised_);
     VIXL_ASSERT(assembler != NULL);
     assembler_ = assembler;
     if (check_policy == kReserveBufferSpace) {
       assembler->GetBuffer()->EnsureSpaceFor(size);
     }
 #ifdef VIXL_DEBUG
     limit_ = assembler_->GetSizeOfCodeGenerated() + size;
     assert_policy_ = size_policy;
     previous_allow_assembler_ = assembler_->AllowAssembler();
     assembler_->SetAllowAssembler(true);
 #else
     USE(size_policy);
 #endif
     initialised_ = true;
   }

   // This function performs the cleaning-up work. It must succeed even if the
   // scope has not been opened. It is safe to call multiple times.
   void Close() {
 #ifdef VIXL_DEBUG
     if (!initialised_) {
       return;
     }
     assembler_->SetAllowAssembler(previous_allow_assembler_);
     switch (assert_policy_) {
       case kNoAssert:
         break;
       case kExactSize:
         VIXL_ASSERT(assembler_->GetSizeOfCodeGenerated() == limit_);
         break;
       case kMaximumSize:
         VIXL_ASSERT(assembler_->GetSizeOfCodeGenerated() <= limit_);
         break;
       default:
         VIXL_UNREACHABLE();
     }
 #endif
     initialised_ = false;
   }

  protected:
   internal::AssemblerBase* assembler_;
   SizePolicy assert_policy_;
   size_t limit_;
   bool previous_allow_assembler_;
   bool initialised_;
 };


 // This scope will:
 // - Do the same as `CodeBufferCheckSCope`, but:
 //   - If managed by VIXL, always reserve space in the `CodeBuffer`.
 //   - Always check the size (exact or maximum) of the generated code on
 //     destruction.
 // - Emit pools if the specified size would push them out of range.
 // - Block pools emission for the duration of the scope.
 // This scope allows the `Assembler` and `MacroAssembler` to be freely and
 // safely mixed for its duration.
 class EmissionCheckScope : public CodeBufferCheckScope {
  public:
   // This constructor implicitly calls `Open` (when `masm` is not `NULL`) to
   // initialise the scope, so it is ready to use immediately after it has been
   // constructed.
   EmissionCheckScope(MacroAssemblerInterface* masm,
                      size_t size,
                      SizePolicy size_policy = kMaximumSize) {
     Open(masm, size, size_policy);
   }

   // This constructor does not implicitly initialise the scope. Instead, the
   // user is required to explicitly call the `Open` function before using the
   // scope.
   EmissionCheckScope() {}

   virtual ~EmissionCheckScope() { Close(); }

   enum PoolPolicy {
     // Do not forbid pool emission inside the scope. Pools will not be emitted
     // on `Open` either.
     kIgnorePools,
     // Force pools to be generated on `Open` if necessary and block their
     // emission inside the scope.
     kBlockPools,
     // Deprecated, but kept for backward compatibility.
     kCheckPools = kBlockPools
   };

   void Open(MacroAssemblerInterface* masm,
             size_t size,
             SizePolicy size_policy = kMaximumSize) {
     Open(masm, size, size_policy, kBlockPools);
   }

   void Close() {
     if (!initialised_) {
       return;
     }
     if (masm_ == NULL) {
       // Nothing to do.
       return;
     }
     // Perform the opposite of `Open`, which is:
     //   - Check the code generation limit was not exceeded.
     //   - Release the pools.
     CodeBufferCheckScope::Close();
     if (pool_policy_ == kBlockPools) {
       masm_->ReleasePools();
     }
     VIXL_ASSERT(!initialised_);
   }

  protected:
   void Open(MacroAssemblerInterface* masm,
             size_t size,
             SizePolicy size_policy,
             PoolPolicy pool_policy) {
     if (masm == NULL) {
       // Nothing to do.
       // We may reach this point in a context of conditional code generation.
       // See `aarch64::MacroAssembler::MoveImmediateHelper()` for an example.
       return;
     }
     masm_ = masm;
     pool_policy_ = pool_policy;
     if (pool_policy_ == kBlockPools) {
       // To avoid duplicating the work to check that enough space is available
       // in the buffer, do not use the more generic `EnsureEmitFor()`. It is
       // done below when opening `CodeBufferCheckScope`.
       masm->EnsureEmitPoolsFor(size);
       masm->BlockPools();
     }
     // The buffer should be checked *after* we emit the pools.
     CodeBufferCheckScope::Open(masm->AsAssemblerBase(),
                                size,
                                kReserveBufferSpace,
                                size_policy);
     VIXL_ASSERT(initialised_);
   }

   // This constructor should only be used from code that is *currently
   // generating* the pools, to avoid an infinite loop.
   EmissionCheckScope(MacroAssemblerInterface* masm,
                      size_t size,
                      SizePolicy size_policy,
                      PoolPolicy pool_policy) {
     Open(masm, size, size_policy, pool_policy);
   }

   MacroAssemblerInterface* masm_;
   PoolPolicy pool_policy_;
 };

 // Use this scope when you need a one-to-one mapping between methods and
 // instructions. This scope will:
 // - Do the same as `EmissionCheckScope`.
 // - Block access to the MacroAssemblerInterface (using run-time assertions).
 class ExactAssemblyScope : public EmissionCheckScope {
  public:
   // This constructor implicitly calls `Open` (when `masm` is not `NULL`) to
   // initialise the scope, so it is ready to use immediately after it has been
   // constructed.
   ExactAssemblyScope(MacroAssemblerInterface* masm,
                      size_t size,
                      SizePolicy size_policy = kExactSize) {
     Open(masm, size, size_policy);
   }

   // This constructor does not implicitly initialise the scope. Instead, the
   // user is required to explicitly call the `Open` function before using the
   // scope.
   ExactAssemblyScope() {}

   virtual ~ExactAssemblyScope() { Close(); }

   void Open(MacroAssemblerInterface* masm,
             size_t size,
             SizePolicy size_policy = kExactSize) {
     Open(masm, size, size_policy, kBlockPools);
   }

   void Close() {
     if (!initialised_) {
       return;
     }
     if (masm_ == NULL) {
       // Nothing to do.
       return;
     }
 #ifdef VIXL_DEBUG
     masm_->SetAllowMacroInstructions(previous_allow_macro_assembler_);
 #else
     USE(previous_allow_macro_assembler_);
 #endif
     EmissionCheckScope::Close();
   }

  protected:
   // This protected constructor allows overriding the pool policy. It is
   // available to allow this scope to be used in code that handles generation
   // of pools.
   ExactAssemblyScope(MacroAssemblerInterface* masm,
                      size_t size,
                      SizePolicy assert_policy,
                      PoolPolicy pool_policy) {
     Open(masm, size, assert_policy, pool_policy);
   }

   void Open(MacroAssemblerInterface* masm,
             size_t size,
             SizePolicy size_policy,
             PoolPolicy pool_policy) {
     VIXL_ASSERT(size_policy != kNoAssert);
     if (masm == NULL) {
       // Nothing to do.
       return;
     }
     // Rely on EmissionCheckScope::Open to initialise `masm_` and
     // `pool_policy_`.
     EmissionCheckScope::Open(masm, size, size_policy, pool_policy);
 #ifdef VIXL_DEBUG
     previous_allow_macro_assembler_ = masm->AllowMacroInstructions();
     masm->SetAllowMacroInstructions(false);
 #endif
   }

  private:
   bool previous_allow_macro_assembler_;
 };


 }  // namespace vixl

 #endif  // VIXL_CODE_GENERATION_SCOPES_H_
	// Copyright 2016, VIXL authors
	// All rights reserved.
	//
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions are met:
	//
	// * Redistributions of source code must retain the above copyright notice,
	// this list of conditions and the following disclaimer.
	// * Redistributions in binary form must reproduce the above copyright notice,
	// this list of conditions and the following disclaimer in the documentation
	// and/or other materials provided with the distribution.
	// * Neither the name of ARM Limited nor the names of its contributors may be
	// used to endorse or promote products derived from this software without
	// specific prior written permission.
	//
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS CONTRIBUTORS "AS IS" AND
	// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
	// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
	// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
	// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
	// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
	// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
	// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


	#ifndef VIXL_CODE_GENERATION_SCOPES_H_
	#define VIXL_CODE_GENERATION_SCOPES_H_


	#include "assembler-base-vixl.h"
	#include "macro-assembler-interface.h"


	namespace vixl {

	// This scope will:
	// - Allow code emission from the specified `Assembler`.
	// - Optionally reserve space in the `CodeBuffer` (if it is managed by VIXL).
	// - Optionally, on destruction, check the size of the generated code.
	// (The size can be either exact or a maximum size.)
	class CodeBufferCheckScope {
	public:
	// Tell whether or not the scope needs to ensure the associated CodeBuffer
	// has enough space for the requested size.
	enum BufferSpacePolicy {
	kReserveBufferSpace,
	kDontReserveBufferSpace,

	// Deprecated, but kept for backward compatibility.
	kCheck = kReserveBufferSpace,
	kNoCheck = kDontReserveBufferSpace
	};

	// Tell whether or not the scope should assert the amount of code emitted
	// within the scope is consistent with the requested amount.
	enum SizePolicy {
	kNoAssert, // Do not check the size of the code emitted.
	kExactSize, // The code emitted must be exactly size bytes.
	kMaximumSize // The code emitted must be at most size bytes.
	};

	// This constructor implicitly calls `Open` to initialise the scope
	// (`assembler` must not be `NULL`), so it is ready to use immediately after
	// it has been constructed.
	CodeBufferCheckScope(internal::AssemblerBase* assembler,
	size_t size,
	BufferSpacePolicy check_policy = kReserveBufferSpace,
	SizePolicy size_policy = kMaximumSize)
	: assembler_(NULL), initialised_(false) {
	Open(assembler, size, check_policy, size_policy);
	}

	// This constructor does not implicitly initialise the scope. Instead, the
	// user is required to explicitly call the `Open` function before using the
	// scope.
	CodeBufferCheckScope() : assembler_(NULL), initialised_(false) {
	// Nothing to do.
	}

	virtual ~CodeBufferCheckScope() { Close(); }

	// This function performs the actual initialisation work.
	void Open(internal::AssemblerBase* assembler,
	size_t size,
	BufferSpacePolicy check_policy = kReserveBufferSpace,
	SizePolicy size_policy = kMaximumSize) {
	VIXL_ASSERT(!initialised_);
	VIXL_ASSERT(assembler != NULL);
	assembler_ = assembler;
	if (check_policy == kReserveBufferSpace) {
	assembler->GetBuffer()->EnsureSpaceFor(size);
	}
	#ifdef VIXL_DEBUG
	limit_ = assembler_->GetSizeOfCodeGenerated() + size;
	assert_policy_ = size_policy;
	previous_allow_assembler_ = assembler_->AllowAssembler();
	assembler_->SetAllowAssembler(true);
	#else
	USE(size_policy);
	#endif
	initialised_ = true;
	}

	// This function performs the cleaning-up work. It must succeed even if the
	// scope has not been opened. It is safe to call multiple times.
	void Close() {
	#ifdef VIXL_DEBUG
	if (!initialised_) {
	return;
	}
	assembler_->SetAllowAssembler(previous_allow_assembler_);
	switch (assert_policy_) {
	case kNoAssert:
	break;
	case kExactSize:
	VIXL_ASSERT(assembler_->GetSizeOfCodeGenerated() == limit_);
	break;
	case kMaximumSize:
	VIXL_ASSERT(assembler_->GetSizeOfCodeGenerated() <= limit_);
	break;
	default:
	VIXL_UNREACHABLE();
	}
	#endif
	initialised_ = false;
	}

	protected:
	internal::AssemblerBase* assembler_;
	SizePolicy assert_policy_;
	size_t limit_;
	bool previous_allow_assembler_;
	bool initialised_;
	};


	// This scope will:
	// - Do the same as `CodeBufferCheckSCope`, but:
	// - If managed by VIXL, always reserve space in the `CodeBuffer`.
	// - Always check the size (exact or maximum) of the generated code on
	// destruction.
	// - Emit pools if the specified size would push them out of range.
	// - Block pools emission for the duration of the scope.
	// This scope allows the `Assembler` and `MacroAssembler` to be freely and
	// safely mixed for its duration.
	class EmissionCheckScope : public CodeBufferCheckScope {
	public:
	// This constructor implicitly calls `Open` (when `masm` is not `NULL`) to
	// initialise the scope, so it is ready to use immediately after it has been
	// constructed.
	EmissionCheckScope(MacroAssemblerInterface* masm,
	size_t size,
	SizePolicy size_policy = kMaximumSize) {
	Open(masm, size, size_policy);
	}

	// This constructor does not implicitly initialise the scope. Instead, the
	// user is required to explicitly call the `Open` function before using the
	// scope.
	EmissionCheckScope() {}

	virtual ~EmissionCheckScope() { Close(); }

	enum PoolPolicy {
	// Do not forbid pool emission inside the scope. Pools will not be emitted
	// on `Open` either.
	kIgnorePools,
	// Force pools to be generated on `Open` if necessary and block their
	// emission inside the scope.
	kBlockPools,
	// Deprecated, but kept for backward compatibility.
	kCheckPools = kBlockPools
	};

	void Open(MacroAssemblerInterface* masm,
	size_t size,
	SizePolicy size_policy = kMaximumSize) {
	Open(masm, size, size_policy, kBlockPools);
	}

	void Close() {
	if (!initialised_) {
	return;
	}
	if (masm_ == NULL) {
	// Nothing to do.
	return;
	}
	// Perform the opposite of `Open`, which is:
	// - Check the code generation limit was not exceeded.
	// - Release the pools.
	CodeBufferCheckScope::Close();
	if (pool_policy_ == kBlockPools) {
	masm_->ReleasePools();
	}
	VIXL_ASSERT(!initialised_);
	}

	protected:
	void Open(MacroAssemblerInterface* masm,
	size_t size,
	SizePolicy size_policy,
	PoolPolicy pool_policy) {
	if (masm == NULL) {
	// Nothing to do.
	// We may reach this point in a context of conditional code generation.
	// See `aarch64::MacroAssembler::MoveImmediateHelper()` for an example.
	return;
	}
	masm_ = masm;
	pool_policy_ = pool_policy;
	if (pool_policy_ == kBlockPools) {
	// To avoid duplicating the work to check that enough space is available
	// in the buffer, do not use the more generic `EnsureEmitFor()`. It is
	// done below when opening `CodeBufferCheckScope`.
	masm->EnsureEmitPoolsFor(size);
	masm->BlockPools();
	}
	// The buffer should be checked after we emit the pools.
	CodeBufferCheckScope::Open(masm->AsAssemblerBase(),
	size,
	kReserveBufferSpace,
	size_policy);
	VIXL_ASSERT(initialised_);
	}

	// This constructor should only be used from code that is *currently
	// generating* the pools, to avoid an infinite loop.
	EmissionCheckScope(MacroAssemblerInterface* masm,
	size_t size,
	SizePolicy size_policy,
	PoolPolicy pool_policy) {
	Open(masm, size, size_policy, pool_policy);
	}

	MacroAssemblerInterface* masm_;
	PoolPolicy pool_policy_;
	};

	// Use this scope when you need a one-to-one mapping between methods and
	// instructions. This scope will:
	// - Do the same as `EmissionCheckScope`.
	// - Block access to the MacroAssemblerInterface (using run-time assertions).
	class ExactAssemblyScope : public EmissionCheckScope {
	public:
	// This constructor implicitly calls `Open` (when `masm` is not `NULL`) to
	// initialise the scope, so it is ready to use immediately after it has been
	// constructed.
	ExactAssemblyScope(MacroAssemblerInterface* masm,
	size_t size,
	SizePolicy size_policy = kExactSize) {
	Open(masm, size, size_policy);
	}

	// This constructor does not implicitly initialise the scope. Instead, the
	// user is required to explicitly call the `Open` function before using the
	// scope.
	ExactAssemblyScope() {}

	virtual ~ExactAssemblyScope() { Close(); }

	void Open(MacroAssemblerInterface* masm,
	size_t size,
	SizePolicy size_policy = kExactSize) {
	Open(masm, size, size_policy, kBlockPools);
	}

	void Close() {
	if (!initialised_) {
	return;
	}
	if (masm_ == NULL) {
	// Nothing to do.
	return;
	}
	#ifdef VIXL_DEBUG
	masm_->SetAllowMacroInstructions(previous_allow_macro_assembler_);
	#else
	USE(previous_allow_macro_assembler_);
	#endif
	EmissionCheckScope::Close();
	}

	protected:
	// This protected constructor allows overriding the pool policy. It is
	// available to allow this scope to be used in code that handles generation
	// of pools.
	ExactAssemblyScope(MacroAssemblerInterface* masm,
	size_t size,
	SizePolicy assert_policy,
	PoolPolicy pool_policy) {
	Open(masm, size, assert_policy, pool_policy);
	}

	void Open(MacroAssemblerInterface* masm,
	size_t size,
	SizePolicy size_policy,
	PoolPolicy pool_policy) {
	VIXL_ASSERT(size_policy != kNoAssert);
	if (masm == NULL) {
	// Nothing to do.
	return;
	}
	// Rely on EmissionCheckScope::Open to initialise `masm_` and
	// `pool_policy_`.
	EmissionCheckScope::Open(masm, size, size_policy, pool_policy);
	#ifdef VIXL_DEBUG
	previous_allow_macro_assembler_ = masm->AllowMacroInstructions();
	masm->SetAllowMacroInstructions(false);
	#endif
	}

	private:
	bool previous_allow_macro_assembler_;
	};


	} // namespace vixl

	#endif // VIXL_CODE_GENERATION_SCOPES_H_