[SystemZ] Support i128 inline asm operands.

Authored by jonpa on Apr 19 2021, 12:31 PM.


[SystemZ] Support i128 inline asm operands.

Support virtual, physical and tied i128 register operands in inline assembly.

i128 is on SystemZ not really supported and is not a legal type and generally
such a value will be split into two i64 parts. There are however some
instructions that require a pair of two GPR64 registers contained in the GR128
bit reg class, which is untyped.

For inline assmebly operands, it proved to be very cumbersome to first follow
the general behavior of splitting an i128 operand into two parts and then
later rebuild the INLINEASM MI to have one GR128 register. Instead, some
minor common code changes were made to SelectionDAGBUilder to only create one
GR128 register part to begin with. In particular:

  • getNumRegisters() now has an optional parameter "RegisterVT" which is passed by AddInlineAsmOperands() and GetRegistersForValue().
  • The bitcasting in GetRegistersForValue is not performed if RegVT is Untyped.
  • The RC for a tied use in AddInlineAsmOperands() is now computed either from the tied def (virtual register), or by getMinimalPhysRegClass() (physical register).
  • InstrEmitter.cpp:EmitCopyFromReg() has been fixed so that the register class (DstRC) can also be computed for an illegal type.

In the SystemZ backend getNumRegisters(), splitValueIntoRegisterParts() and
joinRegisterPartsIntoValue() have been implemented to handle i128 operands.

Differential Revision: https://reviews.llvm.org/D100788

Review: Ulrich Weigand


jonpaMay 26 2021, 8:08 AM
Differential Revision
D100788: [SystemZ] Support i128 inline asm operands
rG8f79203a22d8: [clangd] New ParsingCallback for semantics changes