Author: kib
Date: Wed Oct 28 21:01:00 2020
New Revision: 367115
URL: https://svnweb.freebsd.org/changeset/base/367115
Log:
MFC r366904:
Improve FPU Tag Word reconstruction on i386 to indicate register states.
PR: 250454
Modified:
stable/12/sys/amd64/ia32/ia32_reg.c
stable/12/sys/i386/i386/npx.c
Directory Properties:
stable/12/ (props changed)
Modified: stable/12/sys/amd64/ia32/ia32_reg.c
==============================================================================
--- stable/12/sys/amd64/ia32/ia32_reg.c Wed Oct 28 20:22:20 2020
(r367114)
+++ stable/12/sys/amd64/ia32/ia32_reg.c Wed Oct 28 21:01:00 2020
(r367115)
@@ -146,7 +146,11 @@ fill_fpregs32(struct thread *td, struct fpreg32 *regs)
struct save87 *sv_87;
struct env87 *penv_87;
struct envxmm *penv_xmm;
- int i;
+ struct fpacc87 *fx_reg;
+ int i, st;
+ uint64_t mantissa;
+ uint16_t tw, exp;
+ uint8_t ab_tw;
bzero(regs, sizeof(*regs));
sv_87 = (struct save87 *)regs;
@@ -172,13 +176,39 @@ fill_fpregs32(struct thread *td, struct fpreg32 *regs)
/* Entry into the kernel always sets TF_HASSEGS */
penv_87->en_fos = td->td_frame->tf_ds;
- /* FPU registers and tags */
- penv_87->en_tw = 0xffff;
- for (i = 0; i < 8; ++i) {
- sv_87->sv_ac[i] = sv_fpu->sv_fp[i].fp_acc;
- if ((penv_xmm->en_tw & (1 << i)) != 0)
- penv_87->en_tw &= ~(3 << i * 2);
+ /*
+ * FPU registers and tags.
+ * For ST(i), i = fpu_reg - top; we start with fpu_reg=7.
+ */
+ st = 7 - ((penv_xmm->en_sw >> 11) & 7);
+ ab_tw = penv_xmm->en_tw;
+ tw = 0;
+ for (i = 0x80; i != 0; i >>= 1) {
+ sv_87->sv_ac[st] = sv_fpu->sv_fp[st].fp_acc;
+ tw <<= 2;
+ if ((ab_tw & i) != 0) {
+ /* Non-empty - we need to check ST(i) */
+ fx_reg = &sv_fpu->sv_fp[st].fp_acc;
+ /* The first 64 bits contain the mantissa. */
+ mantissa = *((uint64_t *)fx_reg->fp_bytes);
+ /*
+ * The final 16 bits contain the sign bit and the
exponent.
+ * Mask the sign bit since it is of no consequence to
these
+ * tests.
+ */
+ exp = *((uint16_t *)&fx_reg->fp_bytes[8]) & 0x7fff;
+ if (exp == 0) {
+ if (mantissa == 0)
+ tw |= 1; /* Zero */
+ else
+ tw |= 2; /* Denormal */
+ } else if (exp == 0x7fff)
+ tw |= 2; /* Infinity or NaN */
+ } else
+ tw |= 3; /* Empty */
+ st = (st - 1) & 7;
}
+ penv_87->en_tw = tw;
return (0);
}
Modified: stable/12/sys/i386/i386/npx.c
==============================================================================
--- stable/12/sys/i386/i386/npx.c Wed Oct 28 20:22:20 2020
(r367114)
+++ stable/12/sys/i386/i386/npx.c Wed Oct 28 21:01:00 2020
(r367115)
@@ -1149,7 +1149,11 @@ npx_fill_fpregs_xmm1(struct savexmm *sv_xmm, struct sa
{
struct env87 *penv_87;
struct envxmm *penv_xmm;
- int i;
+ struct fpacc87 *fx_reg;
+ int i, st;
+ uint64_t mantissa;
+ uint16_t tw, exp;
+ uint8_t ab_tw;
penv_87 = &sv_87->sv_env;
penv_xmm = &sv_xmm->sv_env;
@@ -1163,14 +1167,39 @@ npx_fill_fpregs_xmm1(struct savexmm *sv_xmm, struct sa
penv_87->en_foo = penv_xmm->en_foo;
penv_87->en_fos = penv_xmm->en_fos;
- /* FPU registers and tags */
- penv_87->en_tw = 0xffff;
- for (i = 0; i < 8; ++i) {
- sv_87->sv_ac[i] = sv_xmm->sv_fp[i].fp_acc;
- if ((penv_xmm->en_tw & (1 << i)) != 0)
- /* zero and special are set as valid */
- penv_87->en_tw &= ~(3 << i * 2);
+ /*
+ * FPU registers and tags.
+ * For ST(i), i = fpu_reg - top; we start with fpu_reg=7.
+ */
+ st = 7 - ((penv_xmm->en_sw >> 11) & 7);
+ ab_tw = penv_xmm->en_tw;
+ tw = 0;
+ for (i = 0x80; i != 0; i >>= 1) {
+ sv_87->sv_ac[st] = sv_xmm->sv_fp[st].fp_acc;
+ tw <<= 2;
+ if (ab_tw & i) {
+ /* Non-empty - we need to check ST(i) */
+ fx_reg = &sv_xmm->sv_fp[st].fp_acc;
+ /* The first 64 bits contain the mantissa. */
+ mantissa = *((uint64_t *)fx_reg->fp_bytes);
+ /*
+ * The final 16 bits contain the sign bit and the
exponent.
+ * Mask the sign bit since it is of no consequence to
these
+ * tests.
+ */
+ exp = *((uint16_t *)&fx_reg->fp_bytes[8]) & 0x7fff;
+ if (exp == 0) {
+ if (mantissa == 0)
+ tw |= 1; /* Zero */
+ else
+ tw |= 2; /* Denormal */
+ } else if (exp == 0x7fff)
+ tw |= 2; /* Infinity or NaN */
+ } else
+ tw |= 3; /* Empty */
+ st = (st - 1) & 7;
}
+ penv_87->en_tw = tw;
}
void
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