[SystemZ] Introducing assembler dialects for the Z backend
- This patch introduces a different assembler dialect ("hlasm") for z/OS.
The default dialect has now been given the "att" dialect name. For this
appropriate changes have been added to SystemZ.td.
- This patch also makes a few changes to SystemZInstrFormats.td which
restrict a few condition code mnemonics to just the "att" dialect
variant (he, le, lh, nhe, nle, nlh). These extended condition code
mnemonics are not available in HLASM.
- A new private function has been introduced in SystemZAsmParser.cpp to
return the assembler dialect set in SystemZMCAsmInfo.cpp. The reason we
couldn't/haven't explicitly queried the overriden getAssemblerDialect
function from AsmParser is outlined in this thread here. This returned
dialect is directly passed onto the relevant matcher functions which taken
in a variantID, so that the matcher functions can appropriately choose an
instruction based on the variant.
Reviewed By: uweigand
Differential Revision: https://reviews.llvm.org/D94250