[SystemZ] Fold more spills
Add a mapping from register-based <INSN>R instructions to the corresponding
memory-based <INSN>. Use it to cut down on the number of spill loads.
Some instructions extend their operands from smaller fields, so this
required a new TSFlags field to say how big the unextended operand is.
This optimisation doesn't trigger for C(G)R and CL(G)R because in practice
we always combine those instructions with a branch. Adding a test for every
other case probably seems excessive, but it did catch a missed optimisation
for DSGF (fixed in r185435).
llvm-svn: 185529
diff --git a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
index e9829d5..16207b3 100644
--- a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
@@ -397,6 +397,30 @@
}
}
+ // If the spilled operand is the final one, try to change <INSN>R
+ // into <INSN>.
+ int MemOpcode = SystemZ::getMemOpcode(MI->getOpcode());
+ if (MemOpcode >= 0) {
+ unsigned NumOps = MI->getNumExplicitOperands();
+ if (OpNum == NumOps - 1) {
+ const MCInstrDesc &MemDesc = get(MemOpcode);
+ uint64_t AccessBytes = SystemZII::getAccessSize(MemDesc.TSFlags);
+ assert(AccessBytes != 0 && "Size of access should be known");
+ assert(AccessBytes <= Size && "Access outside the frame index");
+ uint64_t Offset = Size - AccessBytes;
+ MachineMemOperand *FrameMMO = getFrameMMO(MF, FrameIndex, Offset,
+ MachineMemOperand::MOLoad);
+ MachineInstrBuilder MIB = BuildMI(MF, MI->getDebugLoc(), get(MemOpcode));
+ for (unsigned I = 0; I < OpNum; ++I)
+ MIB.addOperand(MI->getOperand(I));
+ MIB.addFrameIndex(FrameIndex).addImm(Offset);
+ if (MemDesc.TSFlags & SystemZII::HasIndex)
+ MIB.addReg(0);
+ MIB.addMemOperand(FrameMMO);
+ return MIB;
+ }
+ }
+
return 0;
}