[PowerPC] allow D-form VSX load/store when accessing FrameIndex without offset
VSX D-form load/store instructions of POWER9 require the offset be a multiple of 16 and a helper`isOffsetMultipleOf` is used to check this.
So far, the helper handles FrameIndex + offset case, but not handling FrameIndex without offset case. Due to this, we are missing opportunities to exploit D-form instructions when accessing an object or array allocated on stack.
For example, x-form store (stxvx) is used for int a[4] = {0}; instead of d-form store (stxv). For larger arrays, D-form instruction is not used when accessing the first 16-byte. Using D-form instructions reduces register pressure as well as instructions.
Differential Revision: https://reviews.llvm.org/D45079
llvm-svn: 329377
diff --git a/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp b/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
index ec822aa..bb9d524 100644
--- a/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
@@ -3937,20 +3937,28 @@
else if (STN)
AddrOp = STN->getOperand(2);
+ // If the address points a frame object or a frame object with an offset,
+ // we need to check the object alignment.
short Imm = 0;
- if (AddrOp.getOpcode() == ISD::ADD) {
+ if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(
+ AddrOp.getOpcode() == ISD::ADD ? AddrOp.getOperand(0) :
+ AddrOp)) {
// If op0 is a frame index that is under aligned, we can't do it either,
// because it is translated to r31 or r1 + slot + offset. We won't know the
// slot number until the stack frame is finalized.
- if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(AddrOp.getOperand(0))) {
- const MachineFrameInfo &MFI = CurDAG->getMachineFunction().getFrameInfo();
- unsigned SlotAlign = MFI.getObjectAlignment(FI->getIndex());
- if ((SlotAlign % Val) != 0)
- return false;
- }
- return isIntS16Immediate(AddrOp.getOperand(1), Imm) && !(Imm % Val);
+ const MachineFrameInfo &MFI = CurDAG->getMachineFunction().getFrameInfo();
+ unsigned SlotAlign = MFI.getObjectAlignment(FI->getIndex());
+ if ((SlotAlign % Val) != 0)
+ return false;
+
+ // If we have an offset, we need further check on the offset.
+ if (AddrOp.getOpcode() != ISD::ADD)
+ return true;
}
+ if (AddrOp.getOpcode() == ISD::ADD)
+ return isIntS16Immediate(AddrOp.getOperand(1), Imm) && !(Imm % Val);
+
// If the address comes from the outside, the offset will be zero.
return AddrOp.getOpcode() == ISD::CopyFromReg;
}