<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">m3_cast uses a NOP_EXPR, which assumes no code needs generating to effect the type change (i.e., bits are compatible, no extension necessary, etc.).<div>convert is provided to perform all reasonable conversions. It generates code as necessary (see comments below from c-convert.c).</div><div>Looking at the comments for VIEW_CONVERT_EXPR, I wonder if we should be using that for LOOPHOLE on floats to avoid the need for the temporary?</div><div>I'm not sure we should ever be using CONVERT_EXPR explicitly — probably better to use convert and get the CONVERT_EXPR from that as necessary?</div><div><br></div><div><br></div><div><br></div><div><div>/* Change of width--truncation and extension of integers or reals--</div><div> is represented with NOP_EXPR. Proper functioning of many things</div><div> assumes that no other conversions can be NOP_EXPRs.</div><div><br></div><div> Conversion between integer and pointer is represented with CONVERT_EXPR.</div><div> Converting integer to real uses FLOAT_EXPR</div><div> and real to integer uses FIX_TRUNC_EXPR.</div><div><br></div><div> Here is a list of all the functions that assume that widening and</div><div> narrowing is always done with a NOP_EXPR:</div><div> In convert.c, convert_to_integer.</div><div> In c-typeck.c, build_binary_op (boolean ops), and</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>c_common_truthvalue_conversion.</div><div> In expr.c: expand_expr, for operands of a MULT_EXPR.</div><div> In fold-const.c: fold.</div><div> In tree.c: get_narrower and get_unwidened. */</div><div> </div><div>/* Subroutines of `convert'. */</div></div><div><br></div><div><div> </div><div>/* Create an expression whose value is that of EXPR,</div><div> converted to type TYPE. The TREE_TYPE of the value</div><div> is always TYPE. This function implements all reasonable</div><div> conversions; callers should filter out those that are</div><div> not permitted by the language being compiled. */</div><div><br></div><div>tree</div><div>convert (tree type, tree expr)</div><div><br></div><div><br></div><div>Also:</div><div><br></div><div><span class="Apple-style-span" style="font-family: monospace; ">NOP_EXPR</span></div><dd style="font-family: Times; ">These nodes are used to represent conversions that do not require any code-generation. For example, conversion of a <code>char*</code> to an <code>int*</code> does not require any code be generated; such a conversion is represented by a <code>NOP_EXPR</code>. The single operand is the expression to be converted. The conversion from a pointer to a reference is also represented with a <code>NOP_EXPR</code>. <br></dd><dt style="font-family: Times; "><code>CONVERT_EXPR</code></dt><dd style="font-family: Times; ">These nodes are similar to <code>NOP_EXPR</code>s, but are used in those situations where code may need to be generated. For example, if an <code>int*</code> is converted to an <code>int</code>code may need to be generated on some platforms. These nodes are never used for C++-specific conversions, like conversions between pointers to different classes in an inheritance hierarchy. Any adjustments that need to be made in such cases are always indicated explicitly. Similarly, a user-defined conversion is never represented by a <code>CONVERT_EXPR</code>; instead, the function calls are made explicit. <br></dd><dt style="font-family: Times; "><code>FIXED_CONVERT_EXPR</code></dt><dd style="font-family: Times; ">These nodes are used to represent conversions that involve fixed-point values. For example, from a fixed-point value to another fixed-point value, from an integer to a fixed-point value, from a fixed-point value to an integer, from a floating-point value to a fixed-point value, or from a fixed-point value to a floating-point value. </dd><div><br></div><div><br><div>
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<br><div><div>On 13 Sep 2010, at 06:31, Jay K wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div><br>Tony, et. al. can you help me understand when in parse.c to use "convert" vs. "cast"?<br><br>Thanks,<br> - Jay<br><br><br><br><br> <span class="Apple-tab-span" style="white-space:pre"> </span><span class="Apple-tab-span" style="white-space:pre"> </span> <span class="Apple-tab-span" style="white-space:pre"> </span> <span class="Apple-tab-span" style="white-space:pre"> </span><span class="Apple-tab-span" style="white-space:pre"> </span> <br></div></blockquote></div><br></div></div></body></html>