[llvm] [RISCV][GISEL] Legalize G_EXTRACT_SUBVECTOR (PR #109426)
Craig Topper via llvm-commits
llvm-commits at lists.llvm.org
Mon Sep 23 11:48:27 PDT 2024
================
@@ -931,6 +935,128 @@ bool RISCVLegalizerInfo::legalizeSplatVector(MachineInstr &MI,
return true;
}
+static LLT getLMUL1Ty(LLT VecTy) {
+ assert(VecTy.getElementType().getSizeInBits() <= 64 &&
+ "Unexpected vector LLT");
+ return LLT::scalable_vector(RISCV::RVVBitsPerBlock /
+ VecTy.getElementType().getSizeInBits(),
+ VecTy.getElementType());
+}
+
+bool RISCVLegalizerInfo::legalizeExtractSubvector(MachineInstr &MI,
+ MachineIRBuilder &MIB) const {
+ GExtractSubvector &ES = cast<GExtractSubvector>(MI);
+
+ MachineRegisterInfo &MRI = *MIB.getMRI();
+
+ Register Dst = ES.getReg(0);
+ Register Src = ES.getSrcVec();
+ uint64_t Idx = ES.getIndexImm();
+
+ LLT LitTy = MRI.getType(Dst);
+ LLT BigTy = MRI.getType(Src);
+ Register Vec = Src;
+
+ // We don't have the ability to slide mask vectors down indexed by their i1
+ // elements; the smallest we can do is i8. Often we are able to bitcast to
+ // equivalent i8 vectors.
+ if (LitTy.getElementType() == LLT::scalar(1) && Idx != 0) {
+ auto BigTyMinElts = BigTy.getElementCount().getKnownMinValue();
+ auto LitTyMinElts = LitTy.getElementCount().getKnownMinValue();
+ if (BigTyMinElts >= 8 && LitTyMinElts >= 8) {
+ assert(Idx % 8 == 0 && "Invalid index");
+ assert(BigTyMinElts % 8 == 0 && LitTyMinElts % 8 == 0 &&
+ "Unexpected mask vector lowering");
+ Idx /= 8;
+ BigTy = LLT::vector(BigTy.getElementCount().divideCoefficientBy(8), 8);
+ LitTy = LLT::vector(LitTy.getElementCount().divideCoefficientBy(8), 8);
+ Vec = MIB.buildBitcast(BigTy, Vec).getReg(0);
----------------
topperc wrote:
We can build a new extract_subvector here and let it get legalized on its own. We don't need to continue through the rest of the code.
https://github.com/llvm/llvm-project/pull/109426
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