[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?
From: |
Mattias Engdegård |
Subject: |
bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations? |
Date: |
Sat, 4 Jul 2020 21:01:44 +0200 |
4 juli 2020 kl. 19.00 skrev Paul Eggert <eggert@cs.ucla.edu>:
> Not as far as I know. GCC's -fexcess-precision=standard option tries to do
> that,
> by causing GCC to convert 80-bit results to 64-bit results after every 80-bit
> operation.
Not quite after every operation:
y = x * a + b;
With -fexcess-precision=standard, the 80-bit result of the multiplication will
be used in the addition. With -ffloat-store, a 64-bit store and reload will
take place between the two operations, forcing excess fraction bits to be
discarded.
Another option is to set the Precision Control field in the x87 control word to
53-bit precision; that pretty much eliminates double rounding, but still uses
the extended exponent range (only matters in overflow and underflow cases). And
it may confuse libc's carefully crafted floating-point functions.
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, (continued)
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Paul Eggert, 2020/07/05
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Andreas Schwab, 2020/07/05
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Eli Zaretskii, 2020/07/05
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Stefan Monnier, 2020/07/05
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Paul Eggert, 2020/07/05
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Stefan Monnier, 2020/07/05
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Paul Eggert, 2020/07/05
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Paul Eggert, 2020/07/05
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Andrea Corallo, 2020/07/05
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Paul Eggert, 2020/07/05
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?,
Mattias Engdegård <=
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Eli Zaretskii, 2020/07/04
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Paul Eggert, 2020/07/04
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Philipp Stephani, 2020/07/02
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Mattias Engdegård, 2020/07/03
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Philipp Stephani, 2020/07/25
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Stefan Monnier, 2020/07/25
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Philipp Stephani, 2020/07/25
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Stefan Monnier, 2020/07/25
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Philipp Stephani, 2020/07/25
- bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?, Mattias Engdegård, 2020/07/25