From: Joseph Myers Date: Mon, 4 Nov 2013 16:54:15 +0000 (+0000) Subject: math-emu: fix floating-point to integer overflow detection X-Git-Tag: v3.14-rc1~80^2~5^2~42 X-Git-Url: https://openfabrics.org/gitweb/?a=commitdiff_plain;h=d06b3326dfd02f3f036b670d622fe56eb68a5f30;p=~emulex%2Finfiniband.git math-emu: fix floating-point to integer overflow detection On overflow, the math-emu macro _FP_TO_INT_ROUND tries to saturate its result (subject to the value of rsigned specifying the desired overflow semantics). However, if the rounding step has the effect of increasing the exponent so as to cause overflow (if the rounded result is 1 larger than the largest positive value with the given number of bits, allowing for signedness), the overflow does not get detected, meaning that for unsigned results 0 is produced instead of the maximum unsigned integer with the give number of bits, without an exception being raised for overflow, and that for signed results the minimum (negative) value is produced instead of the maximum (positive) value, again without an exception. This patch makes the code check for rounding increasing the exponent and adjusts the exponent value as needed for the overflow check. Signed-off-by: Joseph Myers Signed-off-by: Scott Wood --- diff --git a/include/math-emu/op-common.h b/include/math-emu/op-common.h index 70fe5e989ac..6bdf8c61d22 100644 --- a/include/math-emu/op-common.h +++ b/include/math-emu/op-common.h @@ -743,12 +743,17 @@ do { \ } \ else \ { \ + int _lz0, _lz1; \ if (X##_e <= -_FP_WORKBITS - 1) \ _FP_FRAC_SET_##wc(X, _FP_MINFRAC_##wc); \ else \ _FP_FRAC_SRS_##wc(X, _FP_FRACBITS_##fs - 1 - X##_e, \ _FP_WFRACBITS_##fs); \ + _FP_FRAC_CLZ_##wc(_lz0, X); \ _FP_ROUND(wc, X); \ + _FP_FRAC_CLZ_##wc(_lz1, X); \ + if (_lz1 < _lz0) \ + X##_e++; /* For overflow detection. */ \ _FP_FRAC_SRL_##wc(X, _FP_WORKBITS); \ _FP_FRAC_ASSEMBLE_##wc(r, X, rsize); \ } \