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Work around a compiler bug in gcc2.6.3 in handling (long long) variables and
shifting. Also correct the original code as Garrett noticed it in mail. Leave the mishandled code in to use it later if future versions of gcc are correct. The code was part of the calibrate_cyclecounter routine to get the speed of the pentium chip.
This commit is contained in:
Andreas Schulz
parent
82c1981ce5
commit
a9700525d8
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=5431
@ -34,7 +34,7 @@
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* SUCH DAMAGE.
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*
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* from: @(#)clock.c 7.2 (Berkeley) 5/12/91
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* $Id: clock.c,v 1.28 1994/11/12 16:24:54 ache Exp $
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* $Id: clock.c,v 1.29 1994/12/30 12:43:34 bde Exp $
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*/
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/*
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@ -292,9 +292,30 @@ calibrate_cyclecounter(void)
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* This assumes that you will never have a clock rate higher
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* than 4GHz, probably a good assumption.
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*/
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cycles_per_sec = (long long)edx + eax;
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cycles_per_sec -= (long long)lastedx + lasteax;
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/* The following C code is correct, but our current gcc 2.6.3
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* seems to produce bad assembly code for it , ATS , XXXX */
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#if 0
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cycles_per_sec = ((long long)edx << 32) + eax;
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cycles_per_sec -= ((long long)lastedx << 32) + lasteax;
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pentium_mhz = ((long)cycles_per_sec + 500000) / 1000000; /* round up */
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#else
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/* produce a workaround for the code above */
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{
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union {
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long long extralong;
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long shorty[2];
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} tmp;
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tmp.shorty[0] = eax;
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tmp.shorty[1] = edx;
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cycles_per_sec = tmp.extralong;
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tmp.shorty[0] = lasteax;
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tmp.shorty[1] = lastedx;
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cycles_per_sec -= tmp.extralong;
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/* round up */
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pentium_mhz = (long) ((cycles_per_sec + 500000) / 1000000);
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}
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#endif
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}
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#endif
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@ -34,7 +34,7 @@
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* SUCH DAMAGE.
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*
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* from: @(#)clock.c 7.2 (Berkeley) 5/12/91
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* $Id: clock.c,v 1.28 1994/11/12 16:24:54 ache Exp $
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* $Id: clock.c,v 1.29 1994/12/30 12:43:34 bde Exp $
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*/
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/*
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@ -292,9 +292,30 @@ calibrate_cyclecounter(void)
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* This assumes that you will never have a clock rate higher
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* than 4GHz, probably a good assumption.
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*/
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cycles_per_sec = (long long)edx + eax;
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cycles_per_sec -= (long long)lastedx + lasteax;
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/* The following C code is correct, but our current gcc 2.6.3
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* seems to produce bad assembly code for it , ATS , XXXX */
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#if 0
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cycles_per_sec = ((long long)edx << 32) + eax;
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cycles_per_sec -= ((long long)lastedx << 32) + lasteax;
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pentium_mhz = ((long)cycles_per_sec + 500000) / 1000000; /* round up */
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#else
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/* produce a workaround for the code above */
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{
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union {
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long long extralong;
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long shorty[2];
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} tmp;
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tmp.shorty[0] = eax;
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tmp.shorty[1] = edx;
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cycles_per_sec = tmp.extralong;
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tmp.shorty[0] = lasteax;
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tmp.shorty[1] = lastedx;
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cycles_per_sec -= tmp.extralong;
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/* round up */
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pentium_mhz = (long) ((cycles_per_sec + 500000) / 1000000);
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}
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#endif
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}
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#endif
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@ -34,7 +34,7 @@
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* SUCH DAMAGE.
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*
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* from: @(#)clock.c 7.2 (Berkeley) 5/12/91
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* $Id: clock.c,v 1.28 1994/11/12 16:24:54 ache Exp $
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* $Id: clock.c,v 1.29 1994/12/30 12:43:34 bde Exp $
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*/
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/*
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@ -292,9 +292,30 @@ calibrate_cyclecounter(void)
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* This assumes that you will never have a clock rate higher
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* than 4GHz, probably a good assumption.
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*/
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cycles_per_sec = (long long)edx + eax;
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cycles_per_sec -= (long long)lastedx + lasteax;
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/* The following C code is correct, but our current gcc 2.6.3
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* seems to produce bad assembly code for it , ATS , XXXX */
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#if 0
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cycles_per_sec = ((long long)edx << 32) + eax;
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cycles_per_sec -= ((long long)lastedx << 32) + lasteax;
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pentium_mhz = ((long)cycles_per_sec + 500000) / 1000000; /* round up */
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#else
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/* produce a workaround for the code above */
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{
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union {
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long long extralong;
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long shorty[2];
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} tmp;
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tmp.shorty[0] = eax;
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tmp.shorty[1] = edx;
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cycles_per_sec = tmp.extralong;
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tmp.shorty[0] = lasteax;
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tmp.shorty[1] = lastedx;
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cycles_per_sec -= tmp.extralong;
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/* round up */
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pentium_mhz = (long) ((cycles_per_sec + 500000) / 1000000);
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}
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#endif
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}
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#endif
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@ -34,7 +34,7 @@
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* SUCH DAMAGE.
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*
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* from: @(#)clock.c 7.2 (Berkeley) 5/12/91
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* $Id: clock.c,v 1.28 1994/11/12 16:24:54 ache Exp $
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* $Id: clock.c,v 1.29 1994/12/30 12:43:34 bde Exp $
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*/
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/*
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@ -292,9 +292,30 @@ calibrate_cyclecounter(void)
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* This assumes that you will never have a clock rate higher
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* than 4GHz, probably a good assumption.
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*/
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cycles_per_sec = (long long)edx + eax;
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cycles_per_sec -= (long long)lastedx + lasteax;
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/* The following C code is correct, but our current gcc 2.6.3
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* seems to produce bad assembly code for it , ATS , XXXX */
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#if 0
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cycles_per_sec = ((long long)edx << 32) + eax;
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cycles_per_sec -= ((long long)lastedx << 32) + lasteax;
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pentium_mhz = ((long)cycles_per_sec + 500000) / 1000000; /* round up */
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#else
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/* produce a workaround for the code above */
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{
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union {
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long long extralong;
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long shorty[2];
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} tmp;
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tmp.shorty[0] = eax;
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tmp.shorty[1] = edx;
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cycles_per_sec = tmp.extralong;
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tmp.shorty[0] = lasteax;
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tmp.shorty[1] = lastedx;
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cycles_per_sec -= tmp.extralong;
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/* round up */
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pentium_mhz = (long) ((cycles_per_sec + 500000) / 1000000);
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}
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#endif
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}
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#endif
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@ -34,7 +34,7 @@
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* SUCH DAMAGE.
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*
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* from: @(#)clock.c 7.2 (Berkeley) 5/12/91
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* $Id: clock.c,v 1.28 1994/11/12 16:24:54 ache Exp $
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* $Id: clock.c,v 1.29 1994/12/30 12:43:34 bde Exp $
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*/
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/*
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@ -292,9 +292,30 @@ calibrate_cyclecounter(void)
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* This assumes that you will never have a clock rate higher
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* than 4GHz, probably a good assumption.
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*/
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cycles_per_sec = (long long)edx + eax;
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cycles_per_sec -= (long long)lastedx + lasteax;
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/* The following C code is correct, but our current gcc 2.6.3
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* seems to produce bad assembly code for it , ATS , XXXX */
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#if 0
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cycles_per_sec = ((long long)edx << 32) + eax;
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cycles_per_sec -= ((long long)lastedx << 32) + lasteax;
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pentium_mhz = ((long)cycles_per_sec + 500000) / 1000000; /* round up */
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#else
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/* produce a workaround for the code above */
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{
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union {
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long long extralong;
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long shorty[2];
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} tmp;
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tmp.shorty[0] = eax;
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tmp.shorty[1] = edx;
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cycles_per_sec = tmp.extralong;
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tmp.shorty[0] = lasteax;
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tmp.shorty[1] = lastedx;
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cycles_per_sec -= tmp.extralong;
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/* round up */
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pentium_mhz = (long) ((cycles_per_sec + 500000) / 1000000);
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}
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#endif
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}
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#endif
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