65 lines
1.9 KiB
C++
65 lines
1.9 KiB
C++
// Copyright (c) the JPEG XL Project Authors. All rights reserved.
|
|
//
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
#ifndef LIB_JXL_BASE_IACA_H_
|
|
#define LIB_JXL_BASE_IACA_H_
|
|
|
|
#include "lib/jxl/base/compiler_specific.h"
|
|
|
|
// IACA (Intel's Code Analyzer) analyzes instruction latencies, but only for
|
|
// code between special markers. These functions embed such markers in an
|
|
// executable, but only for reading via IACA - they deliberately trigger a
|
|
// crash if executed to ensure they are removed in normal builds.
|
|
|
|
#ifndef JXL_IACA_ENABLED
|
|
#define JXL_IACA_ENABLED 0
|
|
#endif
|
|
|
|
namespace jxl {
|
|
|
|
// Call before the region of interest.
|
|
static JXL_INLINE void BeginIACA() {
|
|
#if JXL_IACA_ENABLED && (JXL_COMPILER_GCC || JXL_COMPILER_CLANG)
|
|
asm volatile(
|
|
// UD2 "instruction" raises an invalid opcode exception.
|
|
".byte 0x0F, 0x0B\n\t"
|
|
// Magic sequence recognized by IACA (MOV + addr32 fs:NOP). This actually
|
|
// clobbers EBX, but we don't care because the code won't be run, and we
|
|
// want IACA to observe the same code the compiler would have generated
|
|
// without this marker.
|
|
"movl $111, %%ebx\n\t"
|
|
".byte 0x64, 0x67, 0x90\n\t"
|
|
:
|
|
:
|
|
// (Allegedly) clobbering memory may prevent reordering.
|
|
: "memory");
|
|
#endif
|
|
}
|
|
|
|
// Call after the region of interest.
|
|
static JXL_INLINE void EndIACA() {
|
|
#if JXL_IACA_ENABLED && (JXL_COMPILER_GCC || JXL_COMPILER_CLANG)
|
|
asm volatile(
|
|
// See above.
|
|
"movl $222, %%ebx\n\t"
|
|
".byte 0x64, 0x67, 0x90\n\t"
|
|
// UD2
|
|
".byte 0x0F, 0x0B\n\t"
|
|
:
|
|
:
|
|
// (Allegedly) clobbering memory may prevent reordering.
|
|
: "memory");
|
|
#endif
|
|
}
|
|
|
|
// Add to a scope to mark a region.
|
|
struct ScopeIACA {
|
|
JXL_INLINE ScopeIACA() { BeginIACA(); }
|
|
JXL_INLINE ~ScopeIACA() { EndIACA(); }
|
|
};
|
|
|
|
} // namespace jxl
|
|
|
|
#endif // LIB_JXL_BASE_IACA_H_
|