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Groups > linux.kernel > #1738452
| From | Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH 4.13 027/109] MIPS: math-emu: <MADDF|MSUBF>.S: Fix accuracy (32-bit case) |
| Date | 2017-09-24 23:00 +0200 |
| Message-ID | <utman-50G-55@gated-at.bofh.it> (permalink) |
| References | <utm0F-4Xd-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
4.13-stable review patch. If anyone has any objections, please let me know.
------------------
From: Douglas Leung <douglas.leung@imgtec.com>
commit b3b8e1eb27c523e32b6a8aa7ec8ac4754456af57 upstream.
Implement fused multiply-add with correct accuracy.
Fused multiply-add operation has better accuracy than respective
sequential execution of multiply and add operations applied on the
same inputs. This is because accuracy errors accumulate in latter
case.
This patch implements fused multiply-add with the same accuracy
as it is implemented in hardware, using 64-bit intermediate
calculations.
One test case example (raw bits) that this patch fixes:
MADDF.S fd,fs,ft:
fd = 0x22575225
fs = ft = 0x3727c5ac
Fixes: e24c3bec3e8e ("MIPS: math-emu: Add support for the MIPS R6 MADDF FPU instruction")
Fixes: 83d43305a1df ("MIPS: math-emu: Add support for the MIPS R6 MSUBF FPU instruction")
Signed-off-by: Douglas Leung <douglas.leung@imgtec.com>
Signed-off-by: Miodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: Goran Ferenc <goran.ferenc@imgtec.com>
Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
Cc: Douglas Leung <douglas.leung@imgtec.com>
Cc: Bo Hu <bohu@google.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Jin Qian <jinqian@google.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Petar Jovanovic <petar.jovanovic@imgtec.com>
Cc: Raghu Gandham <raghu.gandham@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/16890/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/mips/math-emu/ieee754sp.h | 4 +
arch/mips/math-emu/sp_maddf.c | 116 ++++++++++++++++-------------------------
2 files changed, 50 insertions(+), 70 deletions(-)
--- a/arch/mips/math-emu/ieee754sp.h
+++ b/arch/mips/math-emu/ieee754sp.h
@@ -45,6 +45,10 @@ static inline int ieee754sp_finite(union
return SPBEXP(x) != SP_EMAX + 1 + SP_EBIAS;
}
+/* 64 bit right shift with rounding */
+#define XSPSRS64(v, rs) \
+ (((rs) >= 64) ? ((v) != 0) : ((v) >> (rs)) | ((v) << (64-(rs)) != 0))
+
/* 3bit extended single precision sticky right shift */
#define XSPSRS(v, rs) \
((rs > (SP_FBITS+3))?1:((v) >> (rs)) | ((v) << (32-(rs)) != 0))
--- a/arch/mips/math-emu/sp_maddf.c
+++ b/arch/mips/math-emu/sp_maddf.c
@@ -21,14 +21,8 @@ static union ieee754sp _sp_maddf(union i
int re;
int rs;
unsigned rm;
- unsigned short lxm;
- unsigned short hxm;
- unsigned short lym;
- unsigned short hym;
- unsigned lrm;
- unsigned hrm;
- unsigned t;
- unsigned at;
+ uint64_t rm64;
+ uint64_t zm64;
int s;
COMPXSP;
@@ -170,108 +164,90 @@ static union ieee754sp _sp_maddf(union i
if (flags & MADDF_NEGATE_PRODUCT)
rs ^= 1;
- /* shunt to top of word */
- xm <<= 32 - (SP_FBITS + 1);
- ym <<= 32 - (SP_FBITS + 1);
+ /* Multiple 24 bit xm and ym to give 48 bit results */
+ rm64 = (uint64_t)xm * ym;
- /*
- * Multiply 32 bits xm, ym to give high 32 bits rm with stickness.
- */
- lxm = xm & 0xffff;
- hxm = xm >> 16;
- lym = ym & 0xffff;
- hym = ym >> 16;
-
- lrm = lxm * lym; /* 16 * 16 => 32 */
- hrm = hxm * hym; /* 16 * 16 => 32 */
-
- t = lxm * hym; /* 16 * 16 => 32 */
- at = lrm + (t << 16);
- hrm += at < lrm;
- lrm = at;
- hrm = hrm + (t >> 16);
-
- t = hxm * lym; /* 16 * 16 => 32 */
- at = lrm + (t << 16);
- hrm += at < lrm;
- lrm = at;
- hrm = hrm + (t >> 16);
-
- rm = hrm | (lrm != 0);
+ /* Shunt to top of word */
+ rm64 = rm64 << 16;
- /*
- * Sticky shift down to normal rounding precision.
- */
- if ((int) rm < 0) {
- rm = (rm >> (32 - (SP_FBITS + 1 + 3))) |
- ((rm << (SP_FBITS + 1 + 3)) != 0);
+ /* Put explicit bit at bit 62 if necessary */
+ if ((int64_t) rm64 < 0) {
+ rm64 = rm64 >> 1;
re++;
- } else {
- rm = (rm >> (32 - (SP_FBITS + 1 + 3 + 1))) |
- ((rm << (SP_FBITS + 1 + 3 + 1)) != 0);
}
- assert(rm & (SP_HIDDEN_BIT << 3));
-
- if (zc == IEEE754_CLASS_ZERO)
- return ieee754sp_format(rs, re, rm);
- /* And now the addition */
+ assert(rm64 & (1 << 62));
- assert(zm & SP_HIDDEN_BIT);
+ if (zc == IEEE754_CLASS_ZERO) {
+ /*
+ * Move explicit bit from bit 62 to bit 26 since the
+ * ieee754sp_format code expects the mantissa to be
+ * 27 bits wide (24 + 3 rounding bits).
+ */
+ rm = XSPSRS64(rm64, (62 - 26));
+ return ieee754sp_format(rs, re, rm);
+ }
- /*
- * Provide guard,round and stick bit space.
- */
- zm <<= 3;
+ /* Move explicit bit from bit 23 to bit 62 */
+ zm64 = (uint64_t)zm << (62 - 23);
+ assert(zm64 & (1 << 62));
+ /* Make the exponents the same */
if (ze > re) {
/*
* Have to shift r fraction right to align.
*/
s = ze - re;
- rm = XSPSRS(rm, s);
+ rm64 = XSPSRS64(rm64, s);
re += s;
} else if (re > ze) {
/*
* Have to shift z fraction right to align.
*/
s = re - ze;
- zm = XSPSRS(zm, s);
+ zm64 = XSPSRS64(zm64, s);
ze += s;
}
assert(ze == re);
assert(ze <= SP_EMAX);
+ /* Do the addition */
if (zs == rs) {
/*
- * Generate 28 bit result of adding two 27 bit numbers
- * leaving result in zm, zs and ze.
+ * Generate 64 bit result by adding two 63 bit numbers
+ * leaving result in zm64, zs and ze.
*/
- zm = zm + rm;
-
- if (zm >> (SP_FBITS + 1 + 3)) { /* carry out */
- zm = XSPSRS1(zm);
+ zm64 = zm64 + rm64;
+ if ((int64_t)zm64 < 0) { /* carry out */
+ zm64 = XSPSRS1(zm64);
ze++;
}
} else {
- if (zm >= rm) {
- zm = zm - rm;
+ if (zm64 >= rm64) {
+ zm64 = zm64 - rm64;
} else {
- zm = rm - zm;
+ zm64 = rm64 - zm64;
zs = rs;
}
- if (zm == 0)
+ if (zm64 == 0)
return ieee754sp_zero(ieee754_csr.rm == FPU_CSR_RD);
/*
- * Normalize in extended single precision
+ * Put explicit bit at bit 62 if necessary.
*/
- while ((zm >> (SP_MBITS + 3)) == 0) {
- zm <<= 1;
+ while ((zm64 >> 62) == 0) {
+ zm64 <<= 1;
ze--;
}
-
}
+
+ /*
+ * Move explicit bit from bit 62 to bit 26 since the
+ * ieee754sp_format code expects the mantissa to be
+ * 27 bits wide (24 + 3 rounding bits).
+ */
+ zm = XSPSRS64(zm64, (62 - 26));
+
return ieee754sp_format(zs, ze, zm);
}
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[PATCH 4.13 000/109] 4.13.4-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 058/109] scsi: qedi: off by one in qedi_get_cmd_from_tid() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 041/109] powerpc/powernv/npu: Move tlb flush before launching ATSD Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 088/109] media: venus: fix copy/paste error in return_buf_error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 066/109] scsi: sg: fixup infoleak when using SG_GET_REQUEST_TABLE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 031/109] crypto: scompress - dont sleep with preemption disabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 060/109] scsi: megaraid_sas: mismatch of allocated MFI frame size and length exposed in MFI MPT pass through command Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 039/109] ext4: fix quota inconsistency during orphan cleanup for read-only mounts Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 067/109] scsi: qla2xxx: Update fw_started flags at qpair creation. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
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[PATCH 4.13 083/109] net/netfilter/nf_conntrack_core: Fix net_conntrack_lock() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 028/109] MIPS: math-emu: <MADDF|MSUBF>.D: Fix accuracy (64-bit case) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 049/109] skd: Submit requests to firmware before triggering the doorbell Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 085/109] s390/mm: fix race on mm->context.flush_mm Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 062/109] scsi: megaraid_sas: Check valid aen class range to avoid kernel panic Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 036/109] wcn36xx: Introduce mutual exclusion of fw configuration Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 037/109] ext4: in ext4_seek_{hole,data}, return -ENXIO for negative offsets Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 078/109] tracing: Fix clear of RECORDED_TGID flag when disabling trace event Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
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[PATCH 4.13 059/109] scsi: aacraid: Fix command send race condition Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 027/109] MIPS: math-emu: <MADDF|MSUBF>.S: Fix accuracy (32-bit case) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 052/109] scsi: zfcp: fix capping of unsuccessful GPN_FT SAN response trace records Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 079/109] tracing: Apply trace_clock changes to instance max buffer Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 055/109] scsi: zfcp: fix payload with full FCP_RSP IU in SCSI trace records Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 026/109] MIPS: math-emu: <MADDF|MSUBF>.<D|S>: Clean up "maddf_flags" enumeration Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 029/109] docs: disable KASLR when debugging kernel Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 043/109] powerpc: Fix DAR reporting when alignment handler faults Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 046/109] md/bitmap: copy correct data for bitmap super Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 075/109] ftrace: Fix selftest goto location on error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 081/109] PCI: shpchp: Enable bridge bus mastering if MSI is enabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
[PATCH 4.13 018/109] MIPS: math-emu: <MAX|MAXA|MIN|MINA>.<D|S>: Fix cases of both inputs zero Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
[PATCH 4.13 024/109] MIPS: math-emu: <MADDF|MSUBF>.<D|S>: Fix some cases of infinite inputs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
[PATCH 4.13 016/109] Input: i8042 - add Gigabyte P57 to the keyboard reset table Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
[PATCH 4.13 008/109] Input: xpad - validate USB endpoint type during probe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
[PATCH 4.13 020/109] MIPS: math-emu: <MAXA|MINA>.<D|S>: Fix cases of input values with opposite signs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
[PATCH 4.13 023/109] MIPS: math-emu: <MADDF|MSUBF>.<D|S>: Fix NaN propagation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
[PATCH 4.13 009/109] drm/amdgpu: read reg in each iterator of psp_wait_for loop Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
[PATCH 4.13 010/109] tty: improve tty_insert_flip_char() fast path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
[PATCH 4.13 014/109] pinctrl: samsung: Fix NULL pointer exception on external interrupts on S3C24xx Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
[PATCH 4.13 022/109] MIPS: math-emu: MINA.<D|S>: Fix some cases of infinity and zero inputs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
[PATCH 4.13 011/109] tty: improve tty_insert_flip_char() slow path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
[PATCH 4.13 019/109] MIPS: math-emu: <MAX|MIN>.<D|S>: Fix cases of both inputs negative Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
[PATCH 4.13 001/109] orangefs: Dont clear SGID when inheriting ACLs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
Re: [PATCH 4.13 001/109] orangefs: Dont clear SGID when inheriting ACLs Mike Marshall <hubcap@omnibond.com> - 2017-09-26 02:10 +0200
[PATCH 4.13 004/109] IB/{qib, hfi1}: Avoid flow control testing for RDMA write operation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
[PATCH 4.13 006/109] srcu: Provide ordering for CPU not involved in grace period Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
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Re: [PATCH 4.13 000/109] 4.13.4-stable review Guenter Roeck <linux@roeck-us.net> - 2017-09-25 03:10 +0200
Re: [PATCH 4.13 000/109] 4.13.4-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-25 08:40 +0200
Re: [PATCH 4.13 000/109] 4.13.4-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-09-26 01:20 +0200
Re: [PATCH 4.13 000/109] 4.13.4-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-26 09:40 +0200
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