From 4f6db5efff8256c7f608285877e892e7e649137a Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Mon, 4 Nov 2013 16:53:50 +0000 Subject: math-emu: fix floating-point to integer unsigned saturation The math-emu macros _FP_TO_INT and _FP_TO_INT_ROUND are supposed to saturate their results for out-of-range arguments, except in the case rsigned == 2 (when instead the low bits of the result are taken). However, in the case rsigned == 0 (converting to unsigned integers), they mistakenly produce 0 for positive results and the maximum unsigned integer for negative results, the opposite of correct unsigned saturation. This patch fixes the logic. Signed-off-by: Joseph Myers Signed-off-by: Scott Wood --- include/math-emu/op-common.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/math-emu/op-common.h') diff --git a/include/math-emu/op-common.h b/include/math-emu/op-common.h index 9696a5e2c437..70fe5e989ace 100644 --- a/include/math-emu/op-common.h +++ b/include/math-emu/op-common.h @@ -685,7 +685,7 @@ do { \ else \ { \ r = 0; \ - if (X##_s) \ + if (!X##_s) \ r = ~r; \ } \ FP_SET_EXCEPTION(FP_EX_INVALID); \ @@ -762,7 +762,7 @@ do { \ if (!rsigned) \ { \ r = 0; \ - if (X##_s) \ + if (!X##_s) \ r = ~r; \ } \ else if (rsigned != 2) \ -- cgit v1.2.1 From d06b3326dfd02f3f036b670d622fe56eb68a5f30 Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Mon, 4 Nov 2013 16:54:15 +0000 Subject: 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 --- include/math-emu/op-common.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/math-emu/op-common.h') diff --git a/include/math-emu/op-common.h b/include/math-emu/op-common.h index 70fe5e989ace..6bdf8c61d221 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); \ } \ -- cgit v1.2.1