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Remove underflow error in float division with infinite divisor.

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float4_div and float8_div correctly produced zero for zero divided
by infinity, but threw an underflow error for nonzero finite values
divided by infinity.  This seems wrong; at the very least it's
inconsistent with the behavior recently implemented for numeric
infinities.  Remove the error and allow zero to be returned.

This patch also removes a useless isinf() test from the overflow
checks in these functions (non-Inf divided by Inf can't produce Inf).

Extracted from a larger patch; this seems significant outside the
context of geometric operators, so it deserves its own commit.

Kyotaro Horiguchi

Discussion: https://postgr.es/m/CAGf+fX70rWFOk5cd00uMfa__0yP+vtQg5ck7c2Onb-Yczp0URA@mail.gmail.com
This commit is contained in:
Tom Lane
2020-11-04 18:11:15 -05:00
parent 9e38c2bb50
commit fac83dbd6f
6 changed files with 24 additions and 4 deletions
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8
src/include/utils/float.h
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@@ -225,9 +225,9 @@ float4_div(const float4 val1, const float4 val2)
if (unlikely(val2 == 0.0f) && !isnan(val1))
float_zero_divide_error();
result = val1 / val2;
if (unlikely(isinf(result)) && !isinf(val1) && !isinf(val2))
if (unlikely(isinf(result)) && !isinf(val1))
float_overflow_error();
if (unlikely(result == 0.0f) && val1 != 0.0f)
if (unlikely(result == 0.0f) && val1 != 0.0f && !isinf(val2))
float_underflow_error();
return result;
@@ -241,9 +241,9 @@ float8_div(const float8 val1, const float8 val2)
if (unlikely(val2 == 0.0) && !isnan(val1))
float_zero_divide_error();
result = val1 / val2;
if (unlikely(isinf(result)) && !isinf(val1) && !isinf(val2))
if (unlikely(isinf(result)) && !isinf(val1))
float_overflow_error();
if (unlikely(result == 0.0) && val1 != 0.0)
if (unlikely(result == 0.0) && val1 != 0.0 && !isinf(val2))
float_underflow_error();
return result;