[all-commits] [llvm/llvm-project] 01061e: [SystemZ] Improve shouldCoalesce() for i128. (#74942)

[Jonas Paulsson via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 01061ed370448a758ccab89c2fcc31f795d4fe8a
      https://github.com/llvm/llvm-project/commit/01061ed370448a758ccab89c2fcc31f795d4fe8a
  Author: Jonas Paulsson <paulson1 at linux.ibm.com>
  Date:   2023-12-14 (Thu, 14 Dec 2023)

  Changed paths:
    M llvm/lib/Target/SystemZ/SystemZRegisterInfo.cpp
    M llvm/test/CodeGen/SystemZ/atomicrmw-ops-i128.ll
    M llvm/test/CodeGen/SystemZ/atomicrmw-xchg-07.ll

  Log Message:
  -----------
  [SystemZ] Improve shouldCoalesce() for i128. (#74942)

The SystemZ implementation of shouldCoalesce() is merely a workaround
for the fact that regalloc can run out of registers when extending 128-bit
intervals with subreg (GPR64/GPR32) COPYs. 

This patch adds more freedom to the coalescer as it now only checks that
the subreg interval is local to MBB and does not have too many physreg
clobbers.