From 41602807766e253ccb6fb761f3ff12767f786e2c Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Mon, 4 May 2020 23:38:44 +0000 Subject: softfloat: fix floatx80 pseudo-denormal addition / subtraction The softfloat function addFloatx80Sigs, used for addition of values with the same sign and subtraction of values with opposite sign, fails to handle the case where the two values both have biased exponent zero and there is a carry resulting from adding the significands, which can occur if one or both values are pseudo-denormals (biased exponent zero, explicit integer bit 1). Add a check for that case, so making the results match those seen on x86 hardware for pseudo-denormals. Signed-off-by: Joseph Myers Message-Id: Signed-off-by: Richard Henderson --- tests/tcg/i386/test-i386-pseudo-denormal.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) create mode 100644 tests/tcg/i386/test-i386-pseudo-denormal.c (limited to 'tests') diff --git a/tests/tcg/i386/test-i386-pseudo-denormal.c b/tests/tcg/i386/test-i386-pseudo-denormal.c new file mode 100644 index 0000000..cfa2a50 --- /dev/null +++ b/tests/tcg/i386/test-i386-pseudo-denormal.c @@ -0,0 +1,24 @@ +/* Test pseudo-denormal operations. */ + +#include +#include + +union u { + struct { uint64_t sig; uint16_t sign_exp; } s; + long double ld; +}; + +volatile union u ld_pseudo_m16382 = { .s = { UINT64_C(1) << 63, 0 } }; + +volatile long double ld_res; + +int main(void) +{ + int ret = 0; + ld_res = ld_pseudo_m16382.ld + ld_pseudo_m16382.ld; + if (ld_res != 0x1p-16381L) { + printf("FAIL: pseudo-denormal add\n"); + ret = 1; + } + return ret; +} -- cgit v1.1