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[174.21.70.228]) by smtp.gmail.com with ESMTPSA id z19sm2231943pjq.11.2021.05.25.08.07.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 May 2021 08:07:14 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Subject: [PATCH v2 11/28] softfloat: Adjust parts_uncanon_normal for floatx80 Date: Tue, 25 May 2021 08:06:49 -0700 Message-Id: <20210525150706.294968-12-richard.henderson@linaro.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210525150706.294968-1-richard.henderson@linaro.org> References: <20210525150706.294968-1-richard.henderson@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::62c; envelope-from=richard.henderson@linaro.org; helo=mail-pl1-x62c.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: alex.bennee@linaro.org, david@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" With floatx80_precision_x, the rounding happens across the break between words. Notice this case with frac_lsb = round_mask + 1 -> 0 and check the bits in frac_hi as needed. In addition, since frac_shift == 0, we won't implicitly clear round_mask via the right-shift, so explicitly clear those bits. This fixes rounding for floatx80_precision_[sd]. Signed-off-by: Richard Henderson Reviewed-by: Alex Bennée --- fpu/softfloat-parts.c.inc | 36 ++++++++++++++++++++++++++++++------ 1 file changed, 30 insertions(+), 6 deletions(-) diff --git a/fpu/softfloat-parts.c.inc b/fpu/softfloat-parts.c.inc index b456c1c30c..8a7f22d6b5 100644 --- a/fpu/softfloat-parts.c.inc +++ b/fpu/softfloat-parts.c.inc @@ -156,7 +156,13 @@ static void partsN(uncanon_normal)(FloatPartsN *p, float_status *s, switch (s->float_rounding_mode) { case float_round_nearest_even: overflow_norm = false; - inc = ((p->frac_lo & roundeven_mask) != frac_lsbm1 ? frac_lsbm1 : 0); + if (N > 64 && frac_lsb == 0) { + inc = ((p->frac_hi & 1) || (p->frac_lo & round_mask) != frac_lsbm1 + ? frac_lsbm1 : 0); + } else { + inc = ((p->frac_lo & roundeven_mask) != frac_lsbm1 + ? frac_lsbm1 : 0); + } break; case float_round_ties_away: overflow_norm = false; @@ -176,7 +182,11 @@ static void partsN(uncanon_normal)(FloatPartsN *p, float_status *s, break; case float_round_to_odd: overflow_norm = true; - inc = p->frac_lo & frac_lsb ? 0 : round_mask; + if (N > 64 && frac_lsb == 0) { + inc = p->frac_hi & 1 ? 0 : round_mask; + } else { + inc = p->frac_lo & frac_lsb ? 0 : round_mask; + } break; default: g_assert_not_reached(); @@ -191,8 +201,8 @@ static void partsN(uncanon_normal)(FloatPartsN *p, float_status *s, p->frac_hi |= DECOMPOSED_IMPLICIT_BIT; exp++; } + p->frac_lo &= ~round_mask; } - frac_shr(p, frac_shift); if (fmt->arm_althp) { /* ARM Alt HP eschews Inf and NaN for a wider exponent. */ @@ -201,18 +211,21 @@ static void partsN(uncanon_normal)(FloatPartsN *p, float_status *s, flags = float_flag_invalid; exp = exp_max; frac_allones(p); + p->frac_lo &= ~round_mask; } } else if (unlikely(exp >= exp_max)) { flags |= float_flag_overflow | float_flag_inexact; if (overflow_norm) { exp = exp_max - 1; frac_allones(p); + p->frac_lo &= ~round_mask; } else { p->cls = float_class_inf; exp = exp_max; frac_clear(p); } } + frac_shr(p, frac_shift); } else if (s->flush_to_zero) { flags |= float_flag_output_denormal; p->cls = float_class_zero; @@ -232,17 +245,28 @@ static void partsN(uncanon_normal)(FloatPartsN *p, float_status *s, /* Need to recompute round-to-even/round-to-odd. */ switch (s->float_rounding_mode) { case float_round_nearest_even: - inc = ((p->frac_lo & roundeven_mask) != frac_lsbm1 - ? frac_lsbm1 : 0); + if (N > 64 && frac_lsb == 0) { + inc = ((p->frac_hi & 1) || + (p->frac_lo & round_mask) != frac_lsbm1 + ? frac_lsbm1 : 0); + } else { + inc = ((p->frac_lo & roundeven_mask) != frac_lsbm1 + ? frac_lsbm1 : 0); + } break; case float_round_to_odd: - inc = p->frac_lo & frac_lsb ? 0 : round_mask; + if (N > 64 && frac_lsb == 0) { + inc = p->frac_hi & 1 ? 0 : round_mask; + } else { + inc = p->frac_lo & frac_lsb ? 0 : round_mask; + } break; default: break; } flags |= float_flag_inexact; frac_addi(p, p, inc); + p->frac_lo &= ~round_mask; } exp = (p->frac_hi & DECOMPOSED_IMPLICIT_BIT) != 0;