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Enable POPCNT only through Makefile

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Also remove some fallback templates that prevent a
compile error in case the user runs 'make icc-profile-popcnt'
from a non supported machine.

We want to loudly fail in that case instead of silently
fallback in a non-popcount compilation.

Updated documentation too.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2009-11-06 17:23:02 +01:00
parent 53ce6ce49c
commit 7c0cb8e73d
2 changed files with 5 additions and 24 deletions
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26
src/bitcount.h
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@@ -22,19 +22,12 @@
#if !defined(BITCOUNT_H_INCLUDED)
#define BITCOUNT_H_INCLUDED
// To enable POPCNT support uncomment USE_POPCNT define. For PGO compile on a Core i7
// you may want to collect profile data first with USE_POPCNT disabled and then, in a
// second profiling session, with USE_POPCNT enabled so to exercise both paths. Don't
// forget to leave USE_POPCNT enabled for the final optimized compile though ;-)
//#define USE_POPCNT
#include "types.h"
// Select type of intrinsic bit count instruction to use
// Select type of intrinsic bit count instruction to use, see
// README.txt on how to pgo compile with POPCNT support.
#if defined(__INTEL_COMPILER) && defined(IS_64BIT) && defined(USE_POPCNT) // Intel compiler
#if defined(__INTEL_COMPILER) && defined(USE_POPCNT) // Intel compiler
#include <nmmintrin.h>
@@ -45,17 +38,9 @@ inline bool cpu_has_popcnt() {
return (CPUInfo[2] >> 23) & 1;
}
// Define a dummy template to workaround a compile error if _mm_popcnt_u64() is not defined.
//
// If _mm_popcnt_u64() is defined in <nmmintrin.h> it will be choosen first due to
// C++ overload rules that always prefer a function to a template with the same name.
// If not, we avoid a compile error and because cpu_has_popcnt() should return false,
// our templetized _mm_popcnt_u64() is never called anyway.
template<typename T> inline unsigned _mm_popcnt_u64(T) { return 0; } // Is never called
#define POPCNT_INTRINSIC(x) _mm_popcnt_u64(x)
#elif defined(_MSC_VER) && defined(IS_64BIT) && defined(USE_POPCNT) // Microsoft compiler
#elif defined(_MSC_VER) && defined(USE_POPCNT) // Microsoft compiler
#include <intrin.h>
@@ -66,9 +51,6 @@ inline bool cpu_has_popcnt() {
return (CPUInfo[2] >> 23) & 1;
}
// See comment of _mm_popcnt_u64<>() few lines above for an explanation.
template<typename T> inline unsigned __popcnt64(T) { return 0; } // Is never called
#define POPCNT_INTRINSIC(x) __popcnt64(x)
#else // Safe fallback for unsupported compilers or when USE_POPCNT is disabled