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[PATCH v2 5/6] softfloat: return low bits of quotient from floatx80_modr
From: |
Joseph Myers |
Subject: |
[PATCH v2 5/6] softfloat: return low bits of quotient from floatx80_modrem |
Date: |
Mon, 8 Jun 2020 16:57:16 +0000 |
User-agent: |
Alpine 2.21 (DEB 202 2017-01-01) |
Both x87 and m68k need the low parts of the quotient for their
remainder operations. Arrange for floatx80_modrem to track those bits
and return them via a pointer.
The architectures using float32_rem and float64_rem do not appear to
need this information, so the *_rem interface is left unchanged and
the information returned only from floatx80_modrem. The logic used to
determine the low 7 bits of the quotient for m68k
(target/m68k/fpu_helper.c:make_quotient) appears completely bogus (it
looks at the result of converting the remainder to integer, the
quotient having been discarded by that point); this patch does not
change that, but the m68k maintainers may wish to do so.
Signed-off-by: Joseph Myers <joseph@codesourcery.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
fpu/softfloat.c | 23 ++++++++++++++++++-----
include/fpu/softfloat.h | 3 ++-
2 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index 1552241b5e..72f45b0103 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -5684,10 +5684,11 @@ floatx80 floatx80_div(floatx80 a, floatx80 b,
float_status *status)
| `a' with respect to the corresponding value `b'. The operation is performed
| according to the IEC/IEEE Standard for Binary Floating-Point Arithmetic,
| if 'mod' is false; if 'mod' is true, return the remainder based on truncating
-| the quotient toward zero instead.
+| the quotient toward zero instead. '*quotient' is set to the low 64 bits of
+| the absolute value of the integer quotient.
*----------------------------------------------------------------------------*/
-floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod,
+floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod, uint64_t *quotient,
float_status *status)
{
bool aSign, zSign;
@@ -5695,6 +5696,7 @@ floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod,
uint64_t aSig0, aSig1, bSig;
uint64_t q, term0, term1, alternateASig0, alternateASig1;
+ *quotient = 0;
if (floatx80_invalid_encoding(a) || floatx80_invalid_encoding(b)) {
float_raise(float_flag_invalid, status);
return floatx80_default_nan(status);
@@ -5753,7 +5755,7 @@ floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod,
shift128Right( aSig0, 0, 1, &aSig0, &aSig1 );
expDiff = 0;
}
- q = ( bSig <= aSig0 );
+ *quotient = q = ( bSig <= aSig0 );
if ( q ) aSig0 -= bSig;
expDiff -= 64;
while ( 0 < expDiff ) {
@@ -5763,6 +5765,8 @@ floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod,
sub128( aSig0, aSig1, term0, term1, &aSig0, &aSig1 );
shortShift128Left( aSig0, aSig1, 62, &aSig0, &aSig1 );
expDiff -= 62;
+ *quotient <<= 62;
+ *quotient += q;
}
expDiff += 64;
if ( 0 < expDiff ) {
@@ -5776,6 +5780,12 @@ floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool
mod,
++q;
sub128( aSig0, aSig1, term0, term1, &aSig0, &aSig1 );
}
+ if (expDiff < 64) {
+ *quotient <<= expDiff;
+ } else {
+ *quotient = 0;
+ }
+ *quotient += q;
}
else {
term1 = 0;
@@ -5790,6 +5800,7 @@ floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod,
aSig0 = alternateASig0;
aSig1 = alternateASig1;
zSign = ! zSign;
+ ++*quotient;
}
}
return
@@ -5806,7 +5817,8 @@ floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod,
floatx80 floatx80_rem(floatx80 a, floatx80 b, float_status *status)
{
- return floatx80_modrem(a, b, false, status);
+ uint64_t quotient;
+ return floatx80_modrem(a, b, false, "ient, status);
}
/*----------------------------------------------------------------------------
@@ -5817,7 +5829,8 @@ floatx80 floatx80_rem(floatx80 a, floatx80 b,
float_status *status)
floatx80 floatx80_mod(floatx80 a, floatx80 b, float_status *status)
{
- return floatx80_modrem(a, b, true, status);
+ uint64_t quotient;
+ return floatx80_modrem(a, b, true, "ient, status);
}
/*----------------------------------------------------------------------------
diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h
index bff6934d09..ff4e2605b1 100644
--- a/include/fpu/softfloat.h
+++ b/include/fpu/softfloat.h
@@ -687,7 +687,8 @@ floatx80 floatx80_add(floatx80, floatx80, float_status
*status);
floatx80 floatx80_sub(floatx80, floatx80, float_status *status);
floatx80 floatx80_mul(floatx80, floatx80, float_status *status);
floatx80 floatx80_div(floatx80, floatx80, float_status *status);
-floatx80 floatx80_modrem(floatx80, floatx80, bool, float_status *status);
+floatx80 floatx80_modrem(floatx80, floatx80, bool, uint64_t *,
+ float_status *status);
floatx80 floatx80_mod(floatx80, floatx80, float_status *status);
floatx80 floatx80_rem(floatx80, floatx80, float_status *status);
floatx80 floatx80_sqrt(floatx80, float_status *status);
--
2.17.1
--
Joseph S. Myers
joseph@codesourcery.com
- [PATCH v2 0/6] softfloat, target/i386: fprem, fprem1 fixes, Joseph Myers, 2020/06/08
- [PATCH v2 1/6] softfloat: merge floatx80_mod and floatx80_rem, Joseph Myers, 2020/06/08
- [PATCH v2 2/6] softfloat: fix floatx80 remainder pseudo-denormal check for zero, Joseph Myers, 2020/06/08
- [PATCH v2 3/6] softfloat: do not return pseudo-denormal from floatx80 remainder, Joseph Myers, 2020/06/08
- [PATCH v2 4/6] softfloat: do not set denominator high bit for floatx80 remainder, Joseph Myers, 2020/06/08
- [PATCH v2 5/6] softfloat: return low bits of quotient from floatx80_modrem,
Joseph Myers <=
- [PATCH v2 6/6] target/i386: reimplement fprem, fprem1 using floatx80 operations, Joseph Myers, 2020/06/08
- Re: [PATCH v2 0/6] softfloat, target/i386: fprem, fprem1 fixes, Paolo Bonzini, 2020/06/12