This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]
Other format:	[Raw text]

Re: [PATCH 1/8] Document signaling for min, max and ltgt operations

From: Segher Boessenkool <segher at kernel dot crashing dot org>
To: Ilya Leoshkevich <iii at linux dot ibm dot com>
Cc: gcc-patches at gcc dot gnu dot org
Date: Tue, 20 Aug 2019 10:04:33 -0500
Subject: Re: [PATCH 1/8] Document signaling for min, max and ltgt operations
References: <20190820091845.80750-1-iii@linux.ibm.com> <20190820091845.80750-2-iii@linux.ibm.com>

On Tue, Aug 20, 2019 at 11:18:38AM +0200, Ilya Leoshkevich wrote:
> Currently it's not clear whether or not min, max and ltgt should raise
> floating point exceptions when dealing with qNaNs.
> 
> Right now a lot of code assumes that LTGT is signaling: in particular,
> it's generated for ((x < y) || (x > y)), which is signaling. The
> behavior of MIN/MAX is (intentionally?) left unspecified, according to
> commit 64dd117734d0 ("Unconditionally use MAX_EXPR/MIN_EXPR for MAX/MIN
> intrinsics").

The < and > operators separately already can cause exceptions, unless
you use -fno-trapping-math, in which case you cannot have LTGT at all.


Segher

Follow-Ups:
- Re: [PATCH 1/8] Document signaling for min, max and ltgt operations
  - From: Ilya Leoshkevich

References:
- [PATCH 0/8] Use signaling FP comparison instructions
  - From: Ilya Leoshkevich
- [PATCH 1/8] Document signaling for min, max and ltgt operations
  - From: Ilya Leoshkevich

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]