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| -rw-r--r-- | docs/TableGenFundamentals.html | 89 |
1 files changed, 83 insertions, 6 deletions
diff --git a/docs/TableGenFundamentals.html b/docs/TableGenFundamentals.html index 7924bd9a24..860f62093c 100644 --- a/docs/TableGenFundamentals.html +++ b/docs/TableGenFundamentals.html @@ -30,6 +30,7 @@ <li><a href="#valuedef">Value definitions</a></li> <li><a href="#recordlet">'let' expressions</a></li> <li><a href="#templateargs">Class template arguments</a></li> + <li><a href="#multiclass">Multiclass definitions and instances</a></li> </ol></li> <li><a href="#filescope">File scope entities</a> <ol> @@ -102,6 +103,10 @@ TableGen keeps track of all of the classes that are used to build up a definition, so the backend can find all definitions of a particular class, such as "Instruction".</p> +<p><b>TableGen multiclasses</b> are groups of abstract records that are +instantiated all at once. Each instantiation can result in multiple TableGen +definitions.</p> + </div> <!-- ======================================================================= --> @@ -463,16 +468,16 @@ running <tt>tblgen</tt> on the example prints the following definitions:</p> <pre> <b>def</b> bork { <i>// Value</i> - bit isMod = 1; - bit isRef = 0; + <b>bit</b> isMod = 1; + <b>bit</b> isRef = 0; } <b>def</b> hork { <i>// Value</i> - bit isMod = 1; - bit isRef = 1; + <b>bit</b> isMod = 1; + <b>bit</b> isRef = 1; } <b>def</b> zork { <i>// Value</i> - bit isMod = 0; - bit isRef = 1; + <b>bit</b> isMod = 0; + <b>bit</b> isRef = 1; } </pre> @@ -483,6 +488,78 @@ X86 backend.</p> </div> +<!-- --------------------------------------------------------------------------> +<div class="doc_subsubsection"> + <a name="multiclass">Multiclass definitions and instances</a> +</div> + +<div class="doc_text"> + +<p> +While classes with template arguments are a good way to factor commonality +between two instances of a definition, multiclasses allow a convenient notation +for defining multiple definitions at once (instances of implicitly constructed +classes). For example, consider an 3-address instruction set whose instructions +come in two forms: "reg = reg op reg" and "reg = reg op imm" (e.g. SPARC). In +this case, you'd like to specify in one place that this commonality exists, then +in a separate place indicate what all the ops are. +</p> + +<p> +Here is an example TableGen fragment that shows this idea: +</p> + +<pre> +<b>def</b> ops; +<b>def</b> GPR; +<b>def</b> Imm; +<b>class</b> inst<<b>int</b> opc, <b>string</b> asmstr, <b>dag</b> operandlist>; + +<b>multiclass</b> ri_inst<<b>int</b> opc, <b>string</b> asmstr> { + def _rr : inst<opc, !strconcat(asmstr, " $dst, $src1, $src2"), + (ops GPR:$dst, GPR:$src1, GPR:$src2)>; + def _ri : inst<opc, !strconcat(asmstr, " $dst, $src1, $src2"), + (ops GPR:$dst, GPR:$src1, Imm:$src2)>; +} + +// Instantiations of the ri_inst multiclass. +<b>defm</b> ADD : ri_inst<0b111, "add">; +<b>defm</b> SUB : ri_inst<0b101, "sub">; +<b>defm</b> MUL : ri_inst<0b100, "mul">; +... +</pre> + +<p>The name of the resuntant definitions has the multidef fragment names + appended to them, so this defines ADD_rr, ADD_ri, SUB_rr, etc. Using a + multiclass this way is exactly equivalent to instantiating the + classes multiple times yourself, e.g. by writing:</p> + +<pre> +<b>def</b> ops; +<b>def</b> GPR; +<b>def</b> Imm; +<b>class</b> inst<<b>int</b> opc, <b>string</b> asmstr, <b>dag</b> operandlist>; + +<b>class</b> rrinst<<b>int</b> opc, <b>string</b> asmstr> + : inst<opc, !strconcat(asmstr, " $dst, $src1, $src2"), + (ops GPR:$dst, GPR:$src1, GPR:$src2)>; + +<b>class</b> riinst<<b>int</b> opc, <b>string</b> asmstr> + : inst<opc, !strconcat(asmstr, " $dst, $src1, $src2"), + (ops GPR:$dst, GPR:$src1, Imm:$src2)>; + +// Instantiations of the ri_inst multiclass. +<b>def</b> ADD_rr : rrinst<0b111, "add">; +<b>def</b> ADD_ri : riinst<0b111, "add">; +<b>def</b> SUB_rr : rrinst<0b101, "sub">; +<b>def</b> SUB_ri : riinst<0b101, "sub">; +<b>def</b> MUL_rr : rrinst<0b100, "mul">; +<b>def</b> MUL_ri : riinst<0b100, "mul">; +... +</pre> + +</div> + <!-- ======================================================================= --> <div class="doc_subsection"> <a name="filescope">File scope entities</a> |