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libgcc/m68k: Fixes for soft float #93

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libgcc/m68k: Fixes for soft float #93

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862467c
m68k: TARGET_CAN_CHANGE_MODE_CLASS is false for FP regs
keith-packard Dec 29, 2024
c1ea994
libgcc/m68k: Fixes for soft float
keith-packard Dec 29, 2024
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22 changes: 22 additions & 0 deletions gcc/config/m68k/m68k.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -200,6 +200,7 @@ static void m68k_asm_final_postscan_insn (FILE *, rtx_insn *insn, rtx [], int);
static HARD_REG_SET m68k_zero_call_used_regs (HARD_REG_SET);
static machine_mode m68k_c_mode_for_floating_type (enum tree_index);
static bool m68k_use_lra_p (void);
static bool m68k_can_change_mode_class (machine_mode from, machine_mode to, reg_class_t rclass);

/* Initialize the GCC target structure. */

Expand Down Expand Up @@ -370,6 +371,9 @@ static bool m68k_use_lra_p (void);
#undef TARGET_C_MODE_FOR_FLOATING_TYPE
#define TARGET_C_MODE_FOR_FLOATING_TYPE m68k_c_mode_for_floating_type

#undef TARGET_CAN_CHANGE_MODE_CLASS
#define TARGET_CAN_CHANGE_MODE_CLASS m68k_can_change_mode_class

TARGET_GNU_ATTRIBUTES (m68k_attribute_table,
{
/* { name, min_len, max_len, decl_req, type_req, fn_type_req,
Expand Down Expand Up @@ -7269,4 +7273,22 @@ m68k_use_lra_p ()
return m68k_lra_p;
}

/* Implement TARGET_CAN_CHANGE_MODE_CLASS. */

static bool
m68k_can_change_mode_class (machine_mode from,
machine_mode to,
reg_class_t rclass)
{
if (from == to)
return true;

/* 68881 registers can't do subreg at all, as all values are reformatted
to extended precision. */
if (reg_classes_intersect_p(rclass, FP_REGS))
return false;

return true;
}

#include "gt-m68k.h"
78 changes: 36 additions & 42 deletions libgcc/config/m68k/fpgnulib.c
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Original file line number Diff line number Diff line change
Expand Up @@ -449,34 +449,37 @@ __extenddfxf2 (double d)
}

exp = EXPD (dl) - EXCESSD + EXCESSX;
/* Check for underflow and denormals. */
if (exp < 0)

dl.l.upper &= MANTDMASK;

/* Recover from a denorm. */
if (exp == -EXCESSD + EXCESSX)
{
if (exp < -53)
{
ldl.l.middle = 0;
ldl.l.lower = 0;
}
else if (exp < -30)
{
ldl.l.lower = (ldl.l.middle & MANTXMASK) >> ((1 - exp) - 32);
ldl.l.middle &= ~MANTXMASK;
}
else
exp++;
while ((dl.l.upper & HIDDEND) == 0)
{
ldl.l.lower >>= 1 - exp;
ldl.l.lower |= (ldl.l.middle & MANTXMASK) << (32 - (1 - exp));
ldl.l.middle = (ldl.l.middle & ~MANTXMASK) | (ldl.l.middle & MANTXMASK >> (1 - exp));
exp--;
dl.l.upper = (dl.l.upper << 1) | (dl.l.lower >> 31);
dl.l.lower = dl.l.lower << 1;
}
exp = 0;
}

/* Handle inf and NaN */
if (exp == EXPDMASK - EXCESSD + EXCESSX)
exp = EXPXMASK;
else if (exp == EXPDMASK - EXCESSD + EXCESSX)
{
exp = EXPXMASK;
/* Add hidden one bit for NaN */
if (dl.l.upper != 0 || dl.l.lower != 0)
dl.l.upper |= HIDDEND;
}
else
{
dl.l.upper |= HIDDEND;
}

ldl.l.upper |= exp << 16;
ldl.l.middle = HIDDENX;
/* 31-20: # mantissa bits in ldl.l.middle - # mantissa bits in dl.l.upper */
ldl.l.middle |= (dl.l.upper & MANTDMASK) << (31 - 20);
ldl.l.middle = dl.l.upper << (31 - 20);
/* 1+20: explicit-integer-bit + # mantissa bits in dl.l.upper */
ldl.l.middle |= dl.l.lower >> (1 + 20);
/* 32 - 21: # bits of dl.l.lower in ldl.l.middle */
Expand Down Expand Up @@ -508,21 +511,21 @@ __truncxfdf2 (long double ld)
/* Check for underflow and denormals. */
if (exp <= 0)
{
if (exp < -53)
long shift = 1 - exp;
if (shift > 52)
{
ldl.l.middle = 0;
ldl.l.lower = 0;
}
else if (exp < -30)
else if (shift >= 32)
{
ldl.l.lower = (ldl.l.middle & MANTXMASK) >> ((1 - exp) - 32);
ldl.l.middle &= ~MANTXMASK;
ldl.l.lower = (ldl.l.middle) >> (shift - 32);
ldl.l.middle = 0;
}
else
{
ldl.l.lower >>= 1 - exp;
ldl.l.lower |= (ldl.l.middle & MANTXMASK) << (32 - (1 - exp));
ldl.l.middle = (ldl.l.middle & ~MANTXMASK) | (ldl.l.middle & MANTXMASK >> (1 - exp));
ldl.l.lower = (ldl.l.middle << (32 - shift)) | (ldl.l.lower >> shift);
ldl.l.middle = ldl.l.middle >> shift;
}
exp = 0;
}
Expand Down Expand Up @@ -585,36 +588,27 @@ __fixxfsi (long double a)
{
union long_double_long ldl;
long exp;
long l;

ldl.ld = a;

exp = EXPX (ldl);
if (exp == 0 && ldl.l.middle == 0 && ldl.l.lower == 0)
return 0;

exp = exp - EXCESSX - 63;
exp = exp - EXCESSX - 32;

if (exp > 0)
if (exp >= 0)
{
/* Return largest integer. */
return SIGNX (ldl) ? 0x80000000L : 0x7fffffffL;
}

if (exp <= -64)
if (exp <= -32)
return 0;

if (exp <= -32)
{
ldl.l.lower = ldl.l.middle >> (-exp - 32);
}
else if (exp < 0)
{
ldl.l.lower = ldl.l.lower >> -exp;
ldl.l.lower |= ldl.l.middle << (32 + exp);
}
ldl.l.middle >>= -exp;

return SIGNX (ldl) ? -ldl.l.lower : ldl.l.lower;
return SIGNX (ldl) ? -ldl.l.middle : ldl.l.middle;
}

/* The remaining provide crude math support by working in double precision. */
Expand Down
13 changes: 9 additions & 4 deletions libgcc/config/m68k/lb1sf68.S
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Expand Up @@ -635,7 +635,7 @@ SYM (__modsi3):
.globl SYM (_fpCCR)
.globl $_exception_handler

QUIET_NaN = 0xffffffff
QUIET_NaN = 0x7fffffff

D_MAX_EXP = 0x07ff
D_BIAS = 1022
Expand Down Expand Up @@ -700,9 +700,10 @@ Ld$overflow:
PICJUMP $_exception_handler

Ld$underflow:
| Return 0 and set the exception flags
| Return a properly signed 0 and set the exception flags
movel IMM (0),d0
movel d0,d1
orl d7,d0
movew IMM (INEXACT_RESULT+UNDERFLOW),d7
moveq IMM (DOUBLE_FLOAT),d6
PICJUMP $_exception_handler
Expand All @@ -711,6 +712,7 @@ Ld$inop:
| Return a quiet NaN and set the exception flags
movel IMM (QUIET_NaN),d0
movel d0,d1
bset IMM (31),d1
movew IMM (INEXACT_RESULT+INVALID_OPERATION),d7
moveq IMM (DOUBLE_FLOAT),d6
PICJUMP $_exception_handler
Expand Down Expand Up @@ -2082,6 +2084,7 @@ Ldivdf$b$nf:
| If d2 == 0x7ff00000 we have to check d3.
tstl d3 |
bne Ld$inop | if d3 <> 0, b is NaN
movel a0,d7 | put a's sign
bra Ld$underflow | else b is +/-INFINITY, so signal underflow

Ldivdf$a$nf:
Expand Down Expand Up @@ -2187,6 +2190,7 @@ Lround$exit:
#endif
beq 2f | if not loop back
bra 1b |
movel a0,d7 | get back sign bit into d7
bra Ld$underflow | safety check, shouldn't execute '
2: orl d6,d2 | this is a trick so we don't lose '
orl d7,d3 | the bits which were flushed right
Expand Down Expand Up @@ -2549,7 +2553,7 @@ Lround$to$minus:
.globl SYM (_fpCCR)
.globl $_exception_handler

QUIET_NaN = 0xffffffff
QUIET_NaN = 0x7fffffff
SIGNL_NaN = 0x7f800001
INFINITY = 0x7f800000

Expand Down Expand Up @@ -2615,8 +2619,9 @@ Lf$overflow:
PICJUMP $_exception_handler

Lf$underflow:
| Return 0 and set the exception flags
| Return a properly signed 0 and set the exception flags
moveq IMM (0),d0
orl d7,d0
moveq IMM (INEXACT_RESULT+UNDERFLOW),d7
moveq IMM (SINGLE_FLOAT),d6
PICJUMP $_exception_handler
Expand Down