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| Differential D52298
[RISCV][MC] Add support for evaluating constant symbols as immediates ClosedPublic Authored by asb on Sep 20 2018, 5:29 AM.
Details Summary This further improves compatibility with GNU as, allowing input such as the following to be assembled: .equ CONST, 0x123456 li a0, CONST addi a0, a0, %lo(CONST) .equ CONST, 1 slli a0, a0, CONST Note that we don't have perfect compatibility with gas, as it will avoid emitting a relocation in this case: addi a0, a0, %lo(CONST2) .equ CONST2, 0x123456
Diff Detail
Event TimelineHerald added subscribers: jocewei, PkmX, rkruppe and 14 others. · View Herald TranscriptSep 20 2018, 5:29 AM asb added a child revision: D52299: [RISCV][MC] Accept %lo and %pcrel_lo on operands to li.Sep 20 2018, 6:10 AM Comment Actions Hi Alex, another solution could be calling parseExpression for AsmToken::Identifier in RISCVAsmParser::parseImmediate instead of calling parseIdentifier. case AsmToken::String:
case AsmToken::Identifier: {
if (getParser().parseExpression(Res))
return MatchOperand_ParseFail;
break;
}parseExpression will call parsePrimaryExpr which contain the logical to call parseIdentifier and also try to get the symbol value when the symbol is variable. Comment Actions Thanks Shiva, that seems like a better approach. It also allows for parsing CONST+1 etc. This needs more test coverage though. From an initial look, it seems lui a0, CONST+1 has a problem when using parsePrimaryExpr that needs investigating further. Comment Actions As suggested my Shiva, this patch has been updated to allow AsmParser::parseExpression to do the work when parsing an identifier. I mentioned previously that I encountered an issue when trying to switch to this approach, but I'm not longer able to reproduce (so it was probably a mistake on my part). Note that constant symbols can't be used with CSR operations. That would require changes toparseCSRSystemRegister. Same for parseBareSymbol (used in e.g. the call pseudoinstruction). Given that this patch is an incremental improvement that makes sense on its own, I'd prefer to follow up with separate patches for the other cases. Does this look good to you? This revision is now accepted and ready to land.Jan 3 2019, 9:52 PM Closed by commit rL350831: [RISCV][MC] Add support for evaluating constant symbols as immediates (authored by asb). · Explain WhyJan 10 2019, 7:37 AM This revision was automatically updated to reflect the committed changes.
Revision Contents
Diff 181059 llvm/trunk/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
llvm/trunk/test/MC/RISCV/rv32i-aliases-valid.s
llvm/trunk/test/MC/RISCV/rv32i-valid.s
llvm/trunk/test/MC/RISCV/rv64i-aliases-valid.s
llvm/trunk/test/MC/RISCV/rv64i-valid.s
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