diff --git a/core_descs/ExampleRV32K.core_desc b/core_descs/ExampleRV32K.core_desc
new file mode 100644
index 000000000000..5e8db20bf3d6
--- /dev/null
+++ b/core_descs/ExampleRV32K.core_desc
@@ -0,0 +1,62 @@
+// RUN: pattern-gen %s -O 3 --mattr=+m --riscv-xlen 32 | FileCheck --check-prefixes=CHECK-RV32,CHECK-RV32-EXTEND -allow-unused-prefixes %s
+// RUN: pattern-gen %s -O 3 --no-extend --mattr=+m --riscv-xlen 32 | FileCheck --check-prefixes=CHECK-RV32,CHECK-RV32-NOEXTED -allow-unused-prefixes %s
+
+InstructionSet XExampleRV32 extends RISCVBase {
+      instructions {
+        // CHECK-RV32: Pattern for K_LLI: (i32 uimm32:$imm)
+        K_LLI {
+            encoding: 4'b0000 :: imm[31:0] :: rd[4:0] :: 7'b1011111;
+            assembly: {"k.lli", "{name(rd)}, {imm}"};
+            behavior: {
+            if ((rd % RFS) != 0)
+                // imm -> unsigned!
+                // X[rd % RFS] = (unsigned<XLEN>) ((unsigned) imm);
+                X[rd] = (unsigned<XLEN>) ((unsigned) imm);
+            }
+        }
+        // CHECK-RV32: Pattern for K_ADDI: (add GPR:$rs1, (i32 uimm24:$imm))
+        K_ADDI {
+            encoding: 4'b0001 :: imm[23:0] :: rs1[4:0] :: 3'b000 :: rd[4:0] :: 7'b1011111;
+            assembly: {"k.addi", "{name(rd)}, {name(rs1)}, {imm}"};
+            behavior: {
+                if ((rd % RFS) != 0) {
+                    // X[rd % RFS] = X[rs1 % RFS] + (signed)imm;
+                    X[rd] = X[rs1] + (signed)imm;
+                }
+            }
+        }
+        // CHECK-RV32: Pattern for K_ANDI: (and GPR:$rs1, (i32 uimm24:$imm))
+        K_ANDI {
+            encoding: 4'b0001 :: imm[23:0] :: rs1[4:0] :: 3'b001 :: rd[4:0] :: 7'b1011111;
+            assembly: {"k.andi", "{name(rd)}, {name(rs1)}, {imm}"};
+            behavior: {
+                if ((rd % RFS) != 0) {
+                    // X[rd % RFS] = X[rs1 % RFS] & (unsigned)imm;
+                    X[rd] = X[rs1] & (unsigned)imm;
+                }
+            }
+        }
+        // CHECK-RV32: Pattern for K_XORI: (xor GPR:$rs1, (i32 uimm24:$imm))
+        K_XORI {
+            encoding: 4'b0001 :: imm[23:0] :: rs1[4:0] :: 3'b010 :: rd[4:0] :: 7'b1011111;
+            assembly: {"k.xori", "{name(rd)}, {name(rs1)}, {imm}"};
+            behavior: {
+                if ((rd % RFS) != 0) {
+                    // X[rd % RFS] = X[rs1 % RFS] ^ (unsigned)imm;
+                    X[rd] = X[rs1] ^ (unsigned)imm;
+                }
+            }
+        }
+        // CHECK-RV32: Pattern for K_ORI: (or GPR:$rs1, (i32 uimm24:$imm))
+        K_ORI {
+            encoding: 4'b0001 :: imm[23:0] :: rs1[4:0] :: 3'b011 :: rd[4:0] :: 7'b1011111;
+            assembly: {"k.ori", "{name(rd)}, {name(rs1)}, {imm}"};
+            behavior: {
+                if ((rd % RFS) != 0) {
+                    // X[rd % RFS] = X[rs1 % RFS] | (unsigned)imm;
+                    X[rd] = X[rs1] | (unsigned)imm;
+                }
+            }
+        }
+    }
+}
diff --git a/core_descs/ExampleRV32K.ll b/core_descs/ExampleRV32K.ll
new file mode 100644
index 000000000000..13eec3be4fa3
--- /dev/null
+++ b/core_descs/ExampleRV32K.ll
@@ -0,0 +1,86 @@
+; ModuleID = 'mod'
+source_filename = "mod"
+
+define void @implK_LLI(i32 %imm, ptr noalias %rd) {
+  %1 = and i32 %imm, -1
+  %2 = icmp eq i32 %imm, %1
+  call void @llvm.assume(i1 %2)
+  br i1 true, label %3, label %4
+
+3:                                                ; preds = %0
+  store i32 %imm, ptr %rd, align 4
+  br label %4
+
+4:                                                ; preds = %3, %0
+  ret void
+}
+
+; Function Attrs: nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: write)
+declare void @llvm.assume(i1 noundef) #0
+
+define void @implK_ADDI(i32 %imm, ptr %rs1, ptr noalias %rd) {
+  %1 = and i32 %imm, 16777215
+  %2 = icmp eq i32 %imm, %1
+  call void @llvm.assume(i1 %2)
+  br i1 true, label %3, label %5
+
+3:                                                ; preds = %0
+  %rs1.v = load i32, ptr %rs1, align 4
+  %4 = add i32 %rs1.v, %imm
+  store i32 %4, ptr %rd, align 4
+  br label %5
+
+5:                                                ; preds = %3, %0
+  ret void
+}
+
+define void @implK_ANDI(i32 %imm, ptr %rs1, ptr noalias %rd) {
+  %1 = and i32 %imm, 16777215
+  %2 = icmp eq i32 %imm, %1
+  call void @llvm.assume(i1 %2)
+  br i1 true, label %3, label %5
+
+3:                                                ; preds = %0
+  %rs1.v = load i32, ptr %rs1, align 4
+  %4 = and i32 %rs1.v, %imm
+  store i32 %4, ptr %rd, align 4
+  br label %5
+
+5:                                                ; preds = %3, %0
+  ret void
+}
+
+define void @implK_XORI(i32 %imm, ptr %rs1, ptr noalias %rd) {
+  %1 = and i32 %imm, 16777215
+  %2 = icmp eq i32 %imm, %1
+  call void @llvm.assume(i1 %2)
+  br i1 true, label %3, label %5
+
+3:                                                ; preds = %0
+  %rs1.v = load i32, ptr %rs1, align 4
+  %4 = xor i32 %rs1.v, %imm
+  store i32 %4, ptr %rd, align 4
+  br label %5
+
+5:                                                ; preds = %3, %0
+  ret void
+}
+
+define void @implK_ORI(i32 %imm, ptr %rs1, ptr noalias %rd) {
+  %1 = and i32 %imm, 16777215
+  %2 = icmp eq i32 %imm, %1
+  call void @llvm.assume(i1 %2)
+  br i1 true, label %3, label %5
+
+3:                                                ; preds = %0
+  %rs1.v = load i32, ptr %rs1, align 4
+  %4 = or i32 %rs1.v, %imm
+  store i32 %4, ptr %rd, align 4
+  br label %5
+
+5:                                                ; preds = %3, %0
+  ret void
+}
+
+attributes #0 = { nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: write) }
+
diff --git a/core_descs/ExampleRV32K.td b/core_descs/ExampleRV32K.td
new file mode 100644
index 000000000000..31c651a75b75
--- /dev/null
+++ b/core_descs/ExampleRV32K.td
@@ -0,0 +1,33 @@
+let Predicates = [HasVendorXCValu] in {
+
+let hasSideEffects = 0, mayLoad = 0, mayStore = 0, isCodeGenOnly = 1, Constraints = "" in def K_LLI_ : RVInst_K_LLI<(outs GPR:$rd), (ins uimm32:$imm)>;
+
+def : Pat<
+	(i32 (i32 uimm32:$imm)),
+	(K_LLI_ uimm32:$imm)>;
+
+let hasSideEffects = 0, mayLoad = 0, mayStore = 0, isCodeGenOnly = 1, Constraints = "" in def K_ADDI_ : RVInst_K_ADDI<(outs GPR:$rd), (ins uimm24:$imm, GPR:$rs1)>;
+
+def : Pat<
+	(i32 (add GPR:$rs1, (i32 uimm24:$imm))),
+	(K_ADDI_ uimm24:$imm, GPR:$rs1)>;
+
+let hasSideEffects = 0, mayLoad = 0, mayStore = 0, isCodeGenOnly = 1, Constraints = "" in def K_ANDI_ : RVInst_K_ANDI<(outs GPR:$rd), (ins uimm24:$imm, GPR:$rs1)>;
+
+def : Pat<
+	(i32 (and GPR:$rs1, (i32 uimm24:$imm))),
+	(K_ANDI_ uimm24:$imm, GPR:$rs1)>;
+
+let hasSideEffects = 0, mayLoad = 0, mayStore = 0, isCodeGenOnly = 1, Constraints = "" in def K_XORI_ : RVInst_K_XORI<(outs GPR:$rd), (ins uimm24:$imm, GPR:$rs1)>;
+
+def : Pat<
+	(i32 (xor GPR:$rs1, (i32 uimm24:$imm))),
+	(K_XORI_ uimm24:$imm, GPR:$rs1)>;
+
+let hasSideEffects = 0, mayLoad = 0, mayStore = 0, isCodeGenOnly = 1, Constraints = "" in def K_ORI_ : RVInst_K_ORI<(outs GPR:$rd), (ins uimm24:$imm, GPR:$rs1)>;
+
+def : Pat<
+	(i32 (or GPR:$rs1, (i32 uimm24:$imm))),
+	(K_ORI_ uimm24:$imm, GPR:$rs1)>;
+
+}
diff --git a/llvm/tools/pattern-gen/lib/InstrInfo.cpp b/llvm/tools/pattern-gen/lib/InstrInfo.cpp
index 5cb5f2ac5432..0be806004c12 100644
--- a/llvm/tools/pattern-gen/lib/InstrInfo.cpp
+++ b/llvm/tools/pattern-gen/lib/InstrInfo.cpp
@@ -6,8 +6,11 @@ std::string EncodingToTablgen(CDSLInstr const& instr)
 {
     std::stringstream s;
 
+    uint8_t size = instr.size;
+    std::string base = (size == 48 ? "RVInst48" : (size == 16 ? "RVInst16" : "RVInst"));
+
     s << "class RVInst_" << instr.name << "<dag outs, dag ins>"
-      << " : RVInst<outs, ins, \"" << instr.mnemonic << "\", \"" << instr.argString << "\", [], InstFormatOther> {\n";
+      << " : " << base << "<outs, ins, \"" << instr.mnemonic << "\", \"" << instr.argString << "\", [], InstFormatOther> {\n";
 
     for (auto const& f : instr.fields)
         if (f.type & (CDSLInstr::FieldType::NON_CONST))
diff --git a/llvm/tools/pattern-gen/lib/InstrInfo.hpp b/llvm/tools/pattern-gen/lib/InstrInfo.hpp
index 9e26b1d21532..0b080f7d543a 100644
--- a/llvm/tools/pattern-gen/lib/InstrInfo.hpp
+++ b/llvm/tools/pattern-gen/lib/InstrInfo.hpp
@@ -15,7 +15,7 @@ struct CDSLInstr
         uint8_t len;
         uint8_t dstOffset;
         uint8_t srcOffset;
-        uint32_t val;
+        uint64_t val;
     };
 
     enum FieldType
@@ -34,12 +34,13 @@ struct CDSLInstr
     struct Field
     {
         uint8_t len;
-        uint32_t constV;
+        uint64_t constV;
         std::string_view ident;
         uint32_t identIdx;
         FieldType type;
     };
 
+    uint8_t size;
     std::string name;
     std::string mnemonic;
     std::string argString;
diff --git a/llvm/tools/pattern-gen/lib/Parser.cpp b/llvm/tools/pattern-gen/lib/Parser.cpp
index 703f245b1ce9..7a9dfb621eb7 100644
--- a/llvm/tools/pattern-gen/lib/Parser.cpp
+++ b/llvm/tools/pattern-gen/lib/Parser.cpp
@@ -1260,7 +1260,7 @@ void ParseEncoding(TokenStream &ts, CDSLInstr &instr) {
   pop_cur(ts, EncodingKeyword);
   pop_cur(ts, Colon);
 
-  uint offset = 32;
+  uint offset = 48;
   uint preDefIdx = instr.fields.size();
 
   while (1) {
@@ -1329,18 +1329,31 @@ void ParseEncoding(TokenStream &ts, CDSLInstr &instr) {
       syntax_error(ts);
     }
     if (pop_cur_if(ts, Semicolon)) {
-      if (offset != 0)
-        error("instruction length is not 32 bits", ts);
+      if (offset != 0) {
+        if (offset != 16 && offset != 32) {
+          error("instruction length is not 16/32/48 bits", ts);
+        }
+        // Shift the field offsets by 16/32 bits
+        for (auto &frag : instr.frags)
+          if (frag.idx == 255) {
+            frag.srcOffset = frag.srcOffset - offset;
+            frag.dstOffset = frag.dstOffset - offset;
+          } else {
+            frag.dstOffset = frag.dstOffset - offset;
+          }
+      }
       break;
     }
     pop_cur(ts, BitwiseConcat);
   }
+  uint8_t size = 48 - offset;
+  instr.size = size;
 
   // Rather than splitting up the constant bits of the instruction into multiple
-  // fields, we use one trailing constant field of size 32. FieldFragments can
+  // fields, we use one trailing constant field of size 32/48. FieldFragments can
   // index into relevant sections of this single field.
   instr.fields.push_back(CDSLInstr::Field{
-      .len = 32, .constV = 0, .type = CDSLInstr::FieldType::CONST});
+      .len = size, .constV = 0, .type = CDSLInstr::FieldType::CONST});
   if (instr.fields.size() > 255)
     error("too many instruction fields", ts);
   uint8_t constIdx = instr.fields.size() - 1;