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Diffstat (limited to '')
-rw-r--r-- | third_party/jpeg-xl/lib/jxl/base/iaca.h | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/third_party/jpeg-xl/lib/jxl/base/iaca.h b/third_party/jpeg-xl/lib/jxl/base/iaca.h new file mode 100644 index 0000000000..e5732dae5c --- /dev/null +++ b/third_party/jpeg-xl/lib/jxl/base/iaca.h @@ -0,0 +1,65 @@ +// 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_ |