[PATCH] D59324: [GlobalISel][AArch64] Gardening: Factor out code to find lane indices
Jessica Paquette via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Wed Mar 13 13:48:18 PDT 2019
paquette created this revision.
paquette added a reviewer: aemerson.
Herald added subscribers: Petar.Avramovic, hiraditya, kristof.beyls, javed.absar, rovka.
Herald added a project: LLVM.
Some more refactoring for G_INSERT_VECTOR_ELT.
Factor out the code used to find a lane index from `selectExtractElt`. Put it into a more general-purpose `getConstantValueForReg` function.
This will be shared with the code for G_INSERT_VECTOR_ELT.
https://reviews.llvm.org/D59324
Files:
llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
Index: llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
+++ llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
@@ -1818,6 +1818,40 @@
return true;
}
+/// Given a register \p Reg, find the value of a constant defining \p Reg.
+/// Return true if one could be found, and store it in \p Val. Return false
+/// otherwise.
+static bool getConstantValueForReg(unsigned Reg, MachineRegisterInfo &MRI,
+ unsigned &Val) {
+ // Look at the def of the register.
+ MachineInstr *Def = MRI.getVRegDef(Reg);
+ if (!Def)
+ return false;
+
+ // Find the first definition which isn't a copy.
+ if (Def->isCopy()) {
+ Reg = Def->getOperand(1).getReg();
+ auto It = find_if_not(MRI.reg_nodbg_instructions(Reg),
+ [](const MachineInstr &MI) { return MI.isCopy(); });
+ if (It == MRI.reg_instr_nodbg_end()) {
+ LLVM_DEBUG(dbgs() << "Couldn't find non-copy def for register\n");
+ return false;
+ }
+ Def = &*It;
+ }
+
+ // TODO: Handle opcodes other than G_CONSTANT.
+ if (Def->getOpcode() != TargetOpcode::G_CONSTANT) {
+ LLVM_DEBUG(dbgs() << "VRegs defined by anything other than G_CONSTANT "
+ "currently unsupported.\n");
+ return false;
+ }
+
+ // Return the constant value associated with the operand.
+ Val = Def->getOperand(1).getCImm()->getLimitedValue();
+ return true;
+}
+
bool AArch64InstructionSelector::selectExtractElt(
MachineInstr &I, MachineRegisterInfo &MRI) const {
assert(I.getOpcode() == TargetOpcode::G_EXTRACT_VECTOR_ELT &&
@@ -1840,30 +1874,11 @@
return false;
}
- // Find the instruction that defines the constant to extract from. There could
- // be any number of copies between the instruction and the definition of the
- // index. Skip them.
- MachineInstr *LaneDefInst = nullptr;
- for (LaneDefInst = MRI.getVRegDef(LaneIdxOp.getReg());
- LaneDefInst && LaneDefInst->isCopy();
- LaneDefInst = MRI.getVRegDef(LaneDefInst->getOperand(1).getReg())) {
- }
-
- // Did we find a def in the first place? If not, bail.
- if (!LaneDefInst) {
- LLVM_DEBUG(dbgs() << "Did not find VReg definition for " << LaneIdxOp
- << "\n");
+ // Find the index to extract from.
+ unsigned LaneIdx = 0;
+ if (!getConstantValueForReg(LaneIdxOp.getReg(), MRI, LaneIdx))
return false;
- }
-
- // TODO: Handle extracts that don't use G_CONSTANT.
- if (LaneDefInst->getOpcode() != TargetOpcode::G_CONSTANT) {
- LLVM_DEBUG(dbgs() << "VRegs defined by anything other than G_CONSTANT "
- "currently unsupported.\n");
- return false;
- }
- unsigned LaneIdx = LaneDefInst->getOperand(1).getCImm()->getLimitedValue();
unsigned CopyOpc = 0;
unsigned ExtractSubReg = 0;
if (!getLaneCopyOpcode(CopyOpc, ExtractSubReg, NarrowTy.getSizeInBits())) {
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