[RISCV][GISEL] Legalize G_ZEXT, G_SEXT, and G_ANYEXT for scalable vector types

Author: michaelmaitland

llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp

@@ -139,20 +139,21 @@ RISCVLegalizerInfo::RISCVLegalizerInfo(const RISCVSubtarget &ST)
       .clampScalar(0, s32, sXLen)
       .minScalarSameAs(1, 0);
 
+  auto &ExtActions =
+      getActionDefinitionsBuilder({G_ZEXT, G_SEXT, G_ANYEXT})
+          .legalIf(all(typeIsLegalIntOrFPVec(0, IntOrFPVecTys, ST),
+                       typeIsLegalIntOrFPVec(1, IntOrFPVecTys, ST)));
   if (ST.is64Bit()) {
-    getActionDefinitionsBuilder({G_ZEXT, G_SEXT, G_ANYEXT})
-        .legalFor({{sXLen, s32}})
-        .maxScalar(0, sXLen);
-
+    ExtActions.legalFor({{sXLen, s32}});
     getActionDefinitionsBuilder(G_SEXT_INREG)
         .customFor({sXLen})
         .maxScalar(0, sXLen)
         .lower();
   } else {
-    getActionDefinitionsBuilder({G_ZEXT, G_SEXT, G_ANYEXT}).maxScalar(0, sXLen);
-
     getActionDefinitionsBuilder(G_SEXT_INREG).maxScalar(0, sXLen).lower();
   }
+  ExtActions.customIf(typeIsLegalBoolVec(1, BoolVecTys, ST))
+      .maxScalar(0, sXLen);
 
   // Merge/Unmerge
   for (unsigned Op : {G_MERGE_VALUES, G_UNMERGE_VALUES}) {
@@ -570,6 +571,33 @@ bool RISCVLegalizerInfo::legalizeVScale(MachineInstr &MI,
     auto VScale = MIB.buildLShr(XLenTy, VLENB, MIB.buildConstant(XLenTy, 3));
     MIB.buildMul(Dst, VScale, MIB.buildConstant(XLenTy, Val));
   }
+  MI.eraseFromParent();
+  return true;
+}
+
+// Custom-lower extensions from mask vectors by using a vselect either with 1
+// for zero/any-extension or -1 for sign-extension:
+//   (vXiN = (s|z)ext vXi1:vmask) -> (vXiN = vselect vmask, (-1 or 1), 0)
+// Note that any-extension is lowered identically to zero-extension.
+bool RISCVLegalizerInfo::legalizeExt(MachineInstr &MI,
+                                     MachineIRBuilder &MIB) const {
+
+  unsigned Opc = MI.getOpcode();
+  assert(Opc == TargetOpcode::G_ZEXT || Opc == TargetOpcode::G_SEXT ||
+         Opc == TargetOpcode::G_ANYEXT);
+
+  MachineRegisterInfo &MRI = *MIB.getMRI();
+  Register Dst = MI.getOperand(0).getReg();
+  Register Src = MI.getOperand(1).getReg();
+
+  LLT DstTy = MRI.getType(Dst);
+  int64_t ExtTrueVal =
+      Opc == TargetOpcode::G_ZEXT || Opc == TargetOpcode::G_ANYEXT ? 1 : -1;
+  LLT DstEltTy = DstTy.getElementType();
+  auto SplatZero = MIB.buildSplatVector(DstTy, MIB.buildConstant(DstEltTy, 0));
+  auto SplatTrue =
+      MIB.buildSplatVector(DstTy, MIB.buildConstant(DstEltTy, ExtTrueVal));
+  MIB.buildSelect(Dst, Src, SplatTrue, SplatZero);
 
   MI.eraseFromParent();
   return true;
@@ -634,6 +662,10 @@ bool RISCVLegalizerInfo::legalizeCustom(
     return legalizeVAStart(MI, MIRBuilder);
   case TargetOpcode::G_VSCALE:
     return legalizeVScale(MI, MIRBuilder);
+  case TargetOpcode::G_ZEXT:
+  case TargetOpcode::G_SEXT:
+  case TargetOpcode::G_ANYEXT:
+    return legalizeExt(MI, MIRBuilder);
   }
 
   llvm_unreachable("expected switch to return");

llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.h

@@ -43,6 +43,7 @@ class RISCVLegalizerInfo : public LegalizerInfo {
 
   bool legalizeVAStart(MachineInstr &MI, MachineIRBuilder &MIRBuilder) const;
   bool legalizeVScale(MachineInstr &MI, MachineIRBuilder &MIB) const;
+  bool legalizeExt(MachineInstr &MI, MachineIRBuilder &MIRBuilder) const;
 };
 } // end namespace llvm
 #endif