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parisc: avoid undefined shift in cnv_float.h

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The attached change fixes a float conversion problem found running the
GCC testsuite with GCC configured with --with-arch=2.0.

The actual problem occurs for an exponent value of 63. This is the
maximum exponent value that can be passed. This causes a left shift by
32 in the else hunk of the macro. This causes undefined behavior and the
wrong value is returned for dresultB. The fix is the check "exponent <=
62". If the exponent is 63, dresultB is set to 0. The patch also
optimizes the operation a bit by copying "Sall(sgl_value) <<
SGL_EXP_LENGTH" to val, so that sgl_value is not modified.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>
This commit is contained in:
John David Anglin 2012-04-01 12:57:18 -04:00 committed by Helge Deller
parent d287b8750e
commit cabd91c3bb
1 changed files with 5 additions and 6 deletions
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11
arch/parisc/math-emu/cnv_float.h
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@ -347,16 +347,15 @@
Sgl_isinexact_to_fix(sgl_value,exponent)
#define Duint_from_sgl_mantissa(sgl_value,exponent,dresultA,dresultB) \
{Sall(sgl_value) <<= SGL_EXP_LENGTH; /* left-justify */ \
{unsigned int val = Sall(sgl_value) << SGL_EXP_LENGTH; \
if (exponent <= 31) { \
Dintp1(dresultA) = 0; \
Dintp2(dresultB) = (unsigned)Sall(sgl_value) >> (31 - exponent); \
Dintp1(dresultA) = 0; \
Dintp2(dresultB) = val >> (31 - exponent); \
} \
else { \
Dintp1(dresultA) = Sall(sgl_value) >> (63 - exponent); \
Dintp2(dresultB) = Sall(sgl_value) << (exponent - 31); \
Dintp1(dresultA) = val >> (63 - exponent); \
Dintp2(dresultB) = exponent <= 62 ? val << (exponent - 31) : 0; \
} \
Sall(sgl_value) >>= SGL_EXP_LENGTH; /* return to original */ \
}
#define Duint_setzero(dresultA,dresultB) \