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</o:shapelayout></xml><![endif]--></head><body lang=EN-IE link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>I have been reading the “RFC/bikeshedding: Separation of instruction and pattern definitions in LLVM backends” topic with considerable interest. This is an approach I have been considering for taming our own large instruction set, and it looks like it structures our descriptions better than the conventional approach we have used so far.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>However, I have another form of TableGen taming that I would like to do.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>In addition to the separation of instruction from the patterns that use it, I have also got a large number of “instruction groups” that differ in their schedules and operands, but are in all other respects structurally similar.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>For example, I have a large number of load instructions that are almost identical but which are in 5 specific groups:<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span style='font-family:Symbol;color:black;mso-fareast-language:EN-US'><span style='mso-list:Ignore'>·<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>Loads where the memory operand is in a register [LDA]<o:p></o:p></span></p><p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span style='font-family:Symbol;color:black;mso-fareast-language:EN-US'><span style='mso-list:Ignore'>·<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>Loads where the memory operand is in a register and is auto-incremented by an implicit value [LDB]<o:p></o:p></span></p><p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span style='font-family:Symbol;color:black;mso-fareast-language:EN-US'><span style='mso-list:Ignore'>·<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>Loads where the memory operand is in a register and is auto-incremented by a value in another register [LDC]<o:p></o:p></span></p><p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span style='font-family:Symbol;color:black;mso-fareast-language:EN-US'><span style='mso-list:Ignore'>·<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>Loads where the memory operand has a base pointer in a register and an immediate offset [LDD]<o:p></o:p></span></p><p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span style='font-family:Symbol;color:black;mso-fareast-language:EN-US'><span style='mso-list:Ignore'>·<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>Loads where the memory operand has a base pointer in a register and an offset in a register [LDE]<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>If I don’t have the multiple processor versions, I can use ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>class/def</span><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>’ by specifying the appropriate ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>class</span><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>’ for each type of instruction in the group, and then use a common set of ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>def</span><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>’ declarations for them with ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>foreach</span><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>’, for example:<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>// Describe the meta-classes for the LDA group<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>class T_LDA_Type1 : ...<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>class T_LDA_Type2 : ...<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>// Describe the meta-classes for the LDB group<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>class T_LDB_Type1 : ...<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>class T_LDB_Type2 : ...<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>// Describe the meta-classes for the LDC group<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>class T_LDC_Type1 : ...<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>class T_LDC_Type2 : ...<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>// Describe the meta-classes for the LDD group<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>class T_LDD_Type1 : ...<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>class T_LDD_Type2 : ...<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>// Describe the meta-classes for the LDE group<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>class T_LDE_Type1 : ...<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>class T_LDE_Type2 : ...<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>// Share a single set of definitions, but parameterised by meta-class<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>foreach loadOp = ["LDA", "LDB", "LDC", "LDD", "LDE" ] in {<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'> def Prefix_#loadOp#_suffix1 : T_#loadOp#_Type1<...>;<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'> def Prefix_#loadOp#_suffix2 : T_#loadOp#_Type2<...>;<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>}<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>All of the ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>def</span><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>’s pass the same values to the ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>class</span><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>’s, though the ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>class</span><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>’s may ignore some as appropriate. For example, I pass the auto-increment size to each, though only the auto-increment patterns care.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>This neatly allows me to symmetrically manage all the instructions in each of the groups using a single statement of the patterns, and maintain only one fifth of the number of definitions. In my actual source, there are around 50 different types of instruction within each group, so reducing the repetition is quite significant.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>But there is a downside.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>For each of the above I also have variations that are a result of different processor and ISA versions, and because of this I have to use ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>multiclass/defm</span><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>’ to define the descriptions along with ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>Require</span><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>’ predicates. The same approach does not work with ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>multiclass/defm</span><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>’ though, because TableGen does not support ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>foreach</span><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>’ with ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>multiclass/defm</span><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>’.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>I have experimented with adapting TableGen to do this, but I am just not knowledgeable enough about how TableGen works and my attempts have not been successful. Perhaps some of the people debating the separation of instruction and patterns topic might have some insight into how TableGen might be adapted to support ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>foreach</span><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>’ with ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>multiclass/defm</span><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>’ definitions and could advise me how I should do this; or maybe the maintainers of TableGen might consider this something that they would be willing to add to TableGen in the future?<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'>Thanks,<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'> MartinO<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:black;mso-fareast-language:EN-US'><o:p> </o:p></span></p></div></body></html>