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Re: Question on tree-ssa-loop-im.c:for_each_index

From: Richard Henderson <rth at redhat dot com>
To: Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>
Cc: Richard Kenner <kenner at vlsi1 dot ultra dot nyu dot edu>, gcc at gcc dot gnu dot org
Date: Sun, 20 Mar 2005 07:46:49 -0800
Subject: Re: Question on tree-ssa-loop-im.c:for_each_index
References: <10503190023.AA16775@vlsi1.ultra.nyu.edu> <20050319205932.GA15256@atrey.karlin.mff.cuni.cz>

On Sat, Mar 19, 2005 at 09:59:32PM +0100, Zdenek Dvorak wrote:
> > 	x = <VIEW_CONVERT_EXPR some_type> 22;
> 
> what is the semantics of this expression?  Should not this rather be
> 
> x = <NOP_EXPR some_type> 22
> 
> (or just INTEGER_CST:some_type 22)?

The semantics are, exactly,

	union {
	  some_type st;
	  int_type it;
	} u;

	u.it = 22;
	x = u.st;

In many cases we *could* fold the constant, but fold-const.c doesn't 
know much about view_convert_expr so we don't.


r~

References:
- Question on tree-ssa-loop-im.c:for_each_index
  - From: Richard Kenner
- Re: Question on tree-ssa-loop-im.c:for_each_index
  - From: Zdenek Dvorak

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