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From: Michael Hayes <m.hayes@elec.canterbury.ac.nz>
To: law@cygnus.com
Cc: Michael Hayes <m.hayes@elec.canterbury.ac.nz>, egcs@cygnus.com
Subject: Re: Ternary operator in loop condition
Date: Sun, 31 Jan 1999 23:58:00 -0000	[thread overview]
Message-ID: <13980.26939.10991.979841@ongaonga.elec.canterbury.ac.nz> (raw)
In-Reply-To: <23825.916133948@hurl.cygnus.com>

Jeffrey A Law writes:
 >   > build_binary_op in c-typeck.c seems to do the damage.   The next 
 >   > question concerns whether the transformation is useful in general 
 >   > and how it should be disabled without pessimizing other stuff.
 > Where precisely does this happen within build_binary_op?

The transformation (damage) is actually done by fold
(fold-const.c:4222) called from build_binary_op.

i < (a ? b : c) ==>  a ? (i < b) : (i < c)

Now under some circumstances I can see that this generates better code
but it sure makes it harder to determine a loop iteration count.

Michael.

  reply	other threads:[~1999-01-31 23:58 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
1999-01-31 23:58 Michael Hayes
1999-01-31 23:58 ` Jeffrey A Law
1999-01-31 23:58   ` Michael Hayes
1999-01-31 23:58     ` Michael Hayes
1999-01-31 23:58       ` Jeffrey A Law
1999-01-31 23:58         ` Michael Hayes [this message]
1999-01-31 23:58           ` Jeffrey A Law
1999-01-31 23:58             ` Michael Hayes
1999-01-31 23:58               ` Unswitching [Was: Re: Ternary operator in loop condition] Jeffrey A Law
1999-01-31 23:58                 ` Unswitching Michael Hayes
1999-01-31 23:58                   ` Unswitching Jeffrey A Law
1999-01-31 23:58                     ` cmov [Re: Unswitching] Richard Henderson
1999-01-31 23:58     ` Ternary operator in loop condition Jeffrey A Law
1999-01-31 23:58       ` Michael Hayes
1999-01-31 23:58         ` Jeffrey A Law

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