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/* This file is part of the Spring engine (GPL v2 or later), see LICENSE.html */
#include "FPUCheck.h"
#include <cstddef>
#include "System/Log/ILog.h"
#include "lib/streflop/streflop_cond.h"
/**
@brief checks FPU control registers.
@return true if everything is fine, false otherwise
Can be used in an assert() to check the FPU control registers MXCSR and FPUCW,
e.g. `assert(good_fpu_control_registers());'
For reference, the layout of the MXCSR register:
FZ:RC:RC:PM:UM:OM:ZM:DM:IM:Rsvd:PE:UE:OE:ZE:DE:IE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Spring1: 0 0 0 1 1 1 0 1 0 0 0 0 0 0 0 0 = 0x1D00 = 7424
Spring2: 0 0 0 1 1 1 1 1 1 0 0 0 0 0 0 0 = 0x1F80 = 8064
Default: 0 0 0 1 1 1 1 1 1 0 0 0 0 0 0 0 = 0x1F80 = 8064
MaskRsvd:1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 = 0xFF80
And the layout of the 387 FPU control word register:
Rsvd:Rsvd:Rsvd:X:RC:RC:PC:PC:Rsvd:Rsvd:PM:UM:OM:ZM:DM:IM
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Spring1: 0 0 0 0 0 0 0 0 0 0 1 1 1 0 1 0 = 0x003A = 58
Spring2: 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 = 0x003F = 63
Default: 0 0 0 0 0 0 1 1 0 0 1 1 1 1 1 1 = 0x033F = 831
MaskRsvd: 0 0 0 1 1 1 1 1 0 0 1 1 1 1 1 1 = 0x1F3F
Where:
Rsvd - Reserved
FZ - Flush to Zero
RC - Rounding Control
PM - Precision Mask
UM - Underflow Mask
OM - Overflow Mask
ZM - Zerodivide Mask
DM - Denormal Mask
IM - Invalid Mask
PE - Precision Exception
UE - Underflow Exception
OE - Overflow Exception
ZE - Zerodivide Exception
DE - Denormal Exception
IE - Invalid Exception
X - Infinity control (unused on 387 and higher)
PC - Precision Control
Spring1 - Control word used by spring in code in CGame::SimFrame().
Spring2 - Control word used by spring in code everywhere else.
Default - Default control word according to Intel.
MaskRsvd - Masks out the reserved bits.
Source: Intel Architecture Software Development Manual, Volume 1, Basic Architecture
*/
void good_fpu_control_registers(const char* text)
{
// We are paranoid.
// We don't trust the enumeration constants from streflop / (g)libc.
// accepted/syncsafe FPU states:
#if defined(__SUPPORT_SNAN__) && !defined(USE_GML) // -fsignaling-nans
static const int sse_a = (0x1937 & 0xFF80);
static const int sse_b = (0x1925 & 0xFF80);
static const int x87_a = (0x0072 & 0x1F3F);
static const int x87_b = 0x003F;
#else
static const int sse_a = 0x1D00;
static const int sse_b = 0x1F80;
static const int x87_a = 0x003A;
static const int x87_b = 0x003F;
#endif
#if defined(STREFLOP_SSE)
// struct
streflop::fpenv_t fenv;
streflop::fegetenv(&fenv);
bool ret = ((fenv.sse_mode & 0xFF80) == sse_a || (fenv.sse_mode & 0xFF80) == sse_b) &&
((fenv.x87_mode & 0x1F3F) == x87_a || (fenv.x87_mode & 0x1F3F) == x87_b);
if (!ret) {
LOG_L(L_WARNING, "[%s] Sync warning: (env.sse_mode) MXCSR 0x%04X instead of 0x%04X or 0x%04X (\"%s\")", __FUNCTION__, fenv.sse_mode, sse_a, sse_b, text);
LOG_L(L_WARNING, "[%s] Sync warning: (env.x87_mode) FPUCW 0x%04X instead of 0x%04X or 0x%04X (\"%s\")", __FUNCTION__, fenv.x87_mode, x87_a, x87_b, text);
// Set single precision floating point math.
streflop_init<streflop::Simple>();
#if defined(__SUPPORT_SNAN__) && !defined(USE_GML)
streflop::feraiseexcept(streflop::FPU_Exceptions(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW));
#endif
}
#elif defined(STREFLOP_X87)
// short int
streflop::fpenv_t fenv;
streflop::fegetenv(&fenv);
bool ret = (fenv & 0x1F3F) == x87_a || (fenv & 0x1F3F) == x87_b;
if (!ret) {
LOG_L(L_WARNING, "[%s] Sync warning: FPUCW 0x%04X instead of 0x%04X or 0x%04X (\"%s\")", __FUNCTION__, fenv, x87_a, x87_b, text);
// Set single precision floating point math.
streflop_init<streflop::Simple>();
#if defined(__SUPPORT_SNAN__) && !defined(USE_GML)
streflop::feraiseexcept(streflop::FPU_Exceptions(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW));
#endif
}
#endif
}
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