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[POWERPC] Fix rounding bug in emulation for double float operating

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This patch fixes rounding bug in emulation for double float operating on PowerPC platform.

When pack double float operand, it need to truncate the tail due to the limited precision.
If the truncated part is not zero, the last bit of work bit (totally 3 bits) need to '|' 1.

This patch is completed in _FP_FRAC_SRS_2(X,N,sz) (arch/powerpc/math-emu/op-2.h).
Originally the code leftwards rotates the operand to just keep the truncated part,
then check whether it is zero. However, the number it rotates is not correct when
N is not smaller than _FP_W_TYPE_SIZE, and it will cause the work bit '|' 1 in the improper case.

This patch fixes this issue.

Signed-off-by: Liu Yu <b13201@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
This commit is contained in:
Liu Yu 2007-12-10 13:00:52 +08:00 committed by Kumar Gala
parent e8b5f43f7b
commit c896862105
1 changed files with 2 additions and 1 deletions
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3
arch/powerpc/math-emu/op-2.h
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@ -59,7 +59,8 @@
else \
{ \
X##_f0 = (X##_f1 >> ((N) - _FP_W_TYPE_SIZE) | \
(((X##_f1 << (sz - (N))) | X##_f0) != 0)); \
(((X##_f1 << (2 * _FP_W_TYPE_SIZE - (N))) | \
X##_f0) != 0)); \
X##_f1 = 0; \
} \
} while (0)