From patchwork Fri May 6 12:48:14 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Maydell X-Patchwork-Id: 1373 Return-Path: Delivered-To: unknown Received: from imap.gmail.com (74.125.159.109) by localhost6.localdomain6 with IMAP4-SSL; 08 Jun 2011 14:51:30 -0000 Delivered-To: patches@linaro.org Received: by 10.224.184.145 with SMTP id ck17cs137348qab; Fri, 6 May 2011 05:48:18 -0700 (PDT) Received: by 10.227.12.18 with SMTP id v18mr3827000wbv.72.1304686097399; Fri, 06 May 2011 05:48:17 -0700 (PDT) Received: from mnementh.archaic.org.uk (mnementh.archaic.org.uk [81.2.115.146]) by mx.google.com with ESMTPS id d17si8871367wbh.28.2011.05.06.05.48.16 (version=TLSv1/SSLv3 cipher=OTHER); Fri, 06 May 2011 05:48:17 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of pm215@archaic.org.uk designates 81.2.115.146 as permitted sender) client-ip=81.2.115.146; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of pm215@archaic.org.uk designates 81.2.115.146 as permitted sender) smtp.mail=pm215@archaic.org.uk Received: from pm215 by mnementh.archaic.org.uk with local (Exim 4.72) (envelope-from ) id 1QIKS7-0007sm-Fk; Fri, 06 May 2011 13:48:15 +0100 From: Peter Maydell To: qemu-devel@nongnu.org Cc: patches@linaro.org Subject: [PATCH 6/7] softfloat: Add new flag for when denormal result is flushed to zero Date: Fri, 6 May 2011 13:48:14 +0100 Message-Id: <1304686095-30265-7-git-send-email-peter.maydell@linaro.org> X-Mailer: git-send-email 1.7.2.5 In-Reply-To: <1304686095-30265-1-git-send-email-peter.maydell@linaro.org> References: <1304686095-30265-1-git-send-email-peter.maydell@linaro.org> Add a new float_flag_output_denormal which is set when the result of a floating point operation would be denormal but is flushed to zero because we are in flush_to_zero mode. This is necessary because some architectures signal this condition as an underflow and others signal it as an inexact result. Signed-off-by: Peter Maydell --- fpu/softfloat.c | 41 ++++++++++++++++++++++++++++++++++------- fpu/softfloat.h | 3 ++- 2 files changed, 36 insertions(+), 8 deletions(-) diff --git a/fpu/softfloat.c b/fpu/softfloat.c index baba1dc..e3cd8a7 100644 --- a/fpu/softfloat.c +++ b/fpu/softfloat.c @@ -341,7 +341,10 @@ static float32 roundAndPackFloat32( flag zSign, int16 zExp, uint32_t zSig STATUS return packFloat32( zSign, 0xFF, - ( roundIncrement == 0 )); } if ( zExp < 0 ) { - if ( STATUS(flush_to_zero) ) return packFloat32( zSign, 0, 0 ); + if (STATUS(flush_to_zero)) { + float_raise(float_flag_output_denormal STATUS_VAR); + return packFloat32(zSign, 0, 0); + } isTiny = ( STATUS(float_detect_tininess) == float_tininess_before_rounding ) || ( zExp < -1 ) @@ -520,7 +523,10 @@ static float64 roundAndPackFloat64( flag zSign, int16 zExp, uint64_t zSig STATUS return packFloat64( zSign, 0x7FF, - ( roundIncrement == 0 )); } if ( zExp < 0 ) { - if ( STATUS(flush_to_zero) ) return packFloat64( zSign, 0, 0 ); + if (STATUS(flush_to_zero)) { + float_raise(float_flag_output_denormal STATUS_VAR); + return packFloat64(zSign, 0, 0); + } isTiny = ( STATUS(float_detect_tininess) == float_tininess_before_rounding ) || ( zExp < -1 ) @@ -699,7 +705,10 @@ static floatx80 goto overflow; } if ( zExp <= 0 ) { - if ( STATUS(flush_to_zero) ) return packFloatx80( zSign, 0, 0 ); + if (STATUS(flush_to_zero)) { + float_raise(float_flag_output_denormal STATUS_VAR); + return packFloatx80(zSign, 0, 0); + } isTiny = ( STATUS(float_detect_tininess) == float_tininess_before_rounding ) || ( zExp < 0 ) @@ -1030,7 +1039,10 @@ static float128 return packFloat128( zSign, 0x7FFF, 0, 0 ); } if ( zExp < 0 ) { - if ( STATUS(flush_to_zero) ) return packFloat128( zSign, 0, 0, 0 ); + if (STATUS(flush_to_zero)) { + float_raise(float_flag_output_denormal STATUS_VAR); + return packFloat128(zSign, 0, 0, 0); + } isTiny = ( STATUS(float_detect_tininess) == float_tininess_before_rounding ) || ( zExp < -1 ) @@ -1761,7 +1773,12 @@ static float32 addFloat32Sigs( float32 a, float32 b, flag zSign STATUS_PARAM) return a; } if ( aExp == 0 ) { - if ( STATUS(flush_to_zero) ) return packFloat32( zSign, 0, 0 ); + if (STATUS(flush_to_zero)) { + if (aSig | bSig) { + float_raise(float_flag_output_denormal STATUS_VAR); + } + return packFloat32(zSign, 0, 0); + } return packFloat32( zSign, 0, ( aSig + bSig )>>6 ); } zSig = 0x40000000 + aSig + bSig; @@ -3120,7 +3137,12 @@ static float64 addFloat64Sigs( float64 a, float64 b, flag zSign STATUS_PARAM ) return a; } if ( aExp == 0 ) { - if ( STATUS(flush_to_zero) ) return packFloat64( zSign, 0, 0 ); + if (STATUS(flush_to_zero)) { + if (aSig | bSig) { + float_raise(float_flag_output_denormal STATUS_VAR); + } + return packFloat64(zSign, 0, 0); + } return packFloat64( zSign, 0, ( aSig + bSig )>>9 ); } zSig = LIT64( 0x4000000000000000 ) + aSig + bSig; @@ -5282,7 +5304,12 @@ static float128 addFloat128Sigs( float128 a, float128 b, flag zSign STATUS_PARAM } add128( aSig0, aSig1, bSig0, bSig1, &zSig0, &zSig1 ); if ( aExp == 0 ) { - if ( STATUS(flush_to_zero) ) return packFloat128( zSign, 0, 0, 0 ); + if (STATUS(flush_to_zero)) { + if (zSig0 | zSig1) { + float_raise(float_flag_output_denormal STATUS_VAR); + } + return packFloat128(zSign, 0, 0, 0); + } return packFloat128( zSign, 0, zSig0, zSig1 ); } zSig2 = 0; diff --git a/fpu/softfloat.h b/fpu/softfloat.h index 5eff085..58c9b7b 100644 --- a/fpu/softfloat.h +++ b/fpu/softfloat.h @@ -193,7 +193,8 @@ enum { float_flag_overflow = 8, float_flag_underflow = 16, float_flag_inexact = 32, - float_flag_input_denormal = 64 + float_flag_input_denormal = 64, + float_flag_output_denormal = 128 }; typedef struct float_status {