[RISCV] Support codegen for some scalar P extension instructions. (#164359)

This includes sext.b, sext.h, min/max, rev8, clz(w), and abs.

Test cases copied from rv32zbb.ll and rv64zbb.ll and pruned to what was
needed for P. Eventually we should merge these back into a single test
file, but I wanted to keep P separated while it is experimental.

Author: topperc

llvm/lib/Target/RISCV/RISCVFeatures.td

@@ -1124,7 +1124,8 @@ def HasStdExtZbkbOrP
                          "'Base P' (Packed-SIMD)">;
 
 def HasStdExtZbbOrZbkbOrP
-    : Predicate<"Subtarget->HasStdExtZbbOrZbkb()|| Subtarget->hasStdExtP()">,
+    : Predicate<"Subtarget->hasStdExtZbb() || Subtarget->hasStdExtZbkb() || "
+                "Subtarget->hasStdExtP()">,
       AssemblerPredicate<(any_of FeatureStdExtZbb, FeatureStdExtZbkb, FeatureStdExtP),
                          "'Zbb' (Basic Bit-Manipulation) or "
                          "'Zbkb' (Bitmanip instructions for Cryptography) or "

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -318,8 +318,9 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
 
   setOperationAction(ISD::EH_DWARF_CFA, MVT::i32, Custom);
 
-  if (!Subtarget.hasStdExtZbb() && !Subtarget.hasVendorXTHeadBb() &&
-      !Subtarget.hasVendorXqcibm() && !Subtarget.hasVendorXAndesPerf() &&
+  if (!Subtarget.hasStdExtZbb() && !Subtarget.hasStdExtP() &&
+      !Subtarget.hasVendorXTHeadBb() && !Subtarget.hasVendorXqcibm() &&
+      !Subtarget.hasVendorXAndesPerf() &&
       !(Subtarget.hasVendorXCValu() && !Subtarget.is64Bit()))
     setOperationAction(ISD::SIGN_EXTEND_INREG, {MVT::i8, MVT::i16}, Expand);
 
@@ -392,7 +393,7 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
       setOperationAction(ISD::BITREVERSE, MVT::i8, Custom);
   }
 
-  if (Subtarget.hasStdExtZbb() ||
+  if (Subtarget.hasStdExtZbb() || Subtarget.hasStdExtP() ||
       (Subtarget.hasVendorXCValu() && !Subtarget.is64Bit())) {
     setOperationAction({ISD::SMIN, ISD::SMAX, ISD::UMIN, ISD::UMAX}, XLenVT,
                        Legal);
@@ -403,6 +404,9 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
       setOperationAction({ISD::CTTZ, ISD::CTTZ_ZERO_UNDEF}, MVT::i32, Custom);
   } else {
     setOperationAction(ISD::CTTZ, XLenVT, Expand);
+    // If have a CLZW, but not CTZW, custom promote i32.
+    if (Subtarget.hasStdExtP() && Subtarget.is64Bit())
+      setOperationAction({ISD::CTTZ, ISD::CTTZ_ZERO_UNDEF}, MVT::i32, Custom);
   }
 
   if (!Subtarget.hasCPOPLike()) {
@@ -419,13 +423,15 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
     // We need the custom lowering to make sure that the resulting sequence
     // for the 32bit case is efficient on 64bit targets.
     // Use default promotion for i32 without Zbb.
-    if (Subtarget.is64Bit() && Subtarget.hasStdExtZbb())
+    if (Subtarget.is64Bit() &&
+        (Subtarget.hasStdExtZbb() || Subtarget.hasStdExtP()))
       setOperationAction({ISD::CTLZ, ISD::CTLZ_ZERO_UNDEF}, MVT::i32, Custom);
   } else {
     setOperationAction(ISD::CTLZ, XLenVT, Expand);
   }
 
-  if (Subtarget.hasVendorXCValu() && !Subtarget.is64Bit()) {
+  if (Subtarget.hasStdExtP() ||
+      (Subtarget.hasVendorXCValu() && !Subtarget.is64Bit())) {
     setOperationAction(ISD::ABS, XLenVT, Legal);
   } else if (Subtarget.hasShortForwardBranchOpt()) {
     // We can use PseudoCCSUB to implement ABS.
@@ -14669,6 +14675,25 @@ void RISCVTargetLowering::ReplaceNodeResults(SDNode *N,
         DAG.getNode(ISD::ANY_EXTEND, DL, MVT::i64, N->getOperand(0));
     bool IsCTZ =
         N->getOpcode() == ISD::CTTZ || N->getOpcode() == ISD::CTTZ_ZERO_UNDEF;
+
+    // Without Zbb, lower as 32 - clzw(~X & (X-1))
+    if (IsCTZ && !Subtarget.hasStdExtZbb()) {
+      assert(Subtarget.hasStdExtP());
+
+      NewOp0 = DAG.getFreeze(NewOp0);
+      SDValue Not = DAG.getNOT(DL, NewOp0, MVT::i64);
+      SDValue Minus1 = DAG.getNode(ISD::SUB, DL, MVT::i64, NewOp0,
+                                   DAG.getConstant(1, DL, MVT::i64));
+      SDValue And = DAG.getNode(ISD::AND, DL, MVT::i64, Not, Minus1);
+      SDValue CLZW = DAG.getNode(RISCVISD::CLZW, DL, MVT::i64, And);
+      SDValue Sub = DAG.getNode(ISD::SUB, DL, MVT::i64,
+                                DAG.getConstant(32, DL, MVT::i64), CLZW);
+      SDValue Res = DAG.getNode(ISD::SIGN_EXTEND_INREG, DL, MVT::i64, Sub,
+                                DAG.getValueType(MVT::i32));
+      Results.push_back(DAG.getNode(ISD::TRUNCATE, DL, MVT::i32, Res));
+      return;
+    }
+
     unsigned Opc = IsCTZ ? RISCVISD::CTZW : RISCVISD::CLZW;
     SDValue Res = DAG.getNode(Opc, DL, MVT::i64, NewOp0);
     Results.push_back(DAG.getNode(ISD::TRUNCATE, DL, MVT::i32, Res));

llvm/lib/Target/RISCV/RISCVInstrInfoP.td

@@ -1455,3 +1455,11 @@ let Predicates = [HasStdExtP, IsRV32] in {
   def PMAXU_DW     : RVPPairBinaryExchanged_rr<0b1111, 0b01, "pmaxu.dw">;
   def PMAXU_DB     : RVPPairBinaryExchanged_rr<0b1111, 0b10, "pmaxu.db">;
 } // Predicates = [HasStdExtP, IsRV32]
+
+
+//===----------------------------------------------------------------------===//
+// Codegen patterns
+//===----------------------------------------------------------------------===//
+
+let Predicates = [HasStdExtP] in
+def : PatGpr<abs, ABS>;

llvm/lib/Target/RISCV/RISCVInstrInfoZb.td

@@ -599,37 +599,43 @@ def : PatGpr<riscv_zip, ZIP_RV32, i32>;
 def : PatGpr<riscv_unzip, UNZIP_RV32, i32>;
 } // Predicates = [HasStdExtZbkb, IsRV32]
 
-let Predicates = [HasStdExtZbb] in {
+let Predicates = [HasStdExtZbbOrP] in {
 def : PatGpr<ctlz, CLZ>;
+}
+
+let Predicates = [HasStdExtZbb] in {
 def : PatGpr<cttz, CTZ>;
 def : PatGpr<ctpop, CPOP>;
 } // Predicates = [HasStdExtZbb]
 
-let Predicates = [HasStdExtZbb, IsRV64] in {
+let Predicates = [HasStdExtZbbOrP, IsRV64] in {
 def : PatGpr<riscv_clzw, CLZW>;
+}
+
+let Predicates = [HasStdExtZbb, IsRV64] in {
 def : PatGpr<riscv_ctzw, CTZW>;
 def : Pat<(i64 (ctpop (i64 (zexti32 (i64 GPR:$rs1))))), (CPOPW GPR:$rs1)>;
 
 def : Pat<(i64 (riscv_negw_max GPR:$rs1)),
           (MAX GPR:$rs1, (XLenVT (SUBW (XLenVT X0), GPR:$rs1)))>;
 } // Predicates = [HasStdExtZbb, IsRV64]
 
-let Predicates = [HasStdExtZbb] in {
+let Predicates = [HasStdExtZbbOrP] in {
 def : Pat<(XLenVT (sext_inreg GPR:$rs1, i8)), (SEXT_B GPR:$rs1)>;
 def : Pat<(XLenVT (sext_inreg GPR:$rs1, i16)), (SEXT_H GPR:$rs1)>;
 } // Predicates = [HasStdExtZbb]
 
-let Predicates = [HasStdExtZbb] in {
+let Predicates = [HasStdExtZbbOrP] in {
 def : PatGprGpr<smin, MIN>;
 def : PatGprGpr<smax, MAX>;
 def : PatGprGpr<umin, MINU>;
 def : PatGprGpr<umax, MAXU>;
 } // Predicates = [HasStdExtZbb]
 
-let Predicates = [HasStdExtZbbOrZbkb, IsRV32] in
+let Predicates = [HasStdExtZbbOrZbkbOrP, IsRV32] in
 def : PatGpr<bswap, REV8_RV32, i32>;
 
-let Predicates = [HasStdExtZbbOrZbkb, IsRV64] in
+let Predicates = [HasStdExtZbbOrZbkbOrP, IsRV64] in
 def : PatGpr<bswap, REV8_RV64, i64>;
 
 let Predicates = [HasStdExtZbkb] in {

llvm/lib/Target/RISCV/RISCVSubtarget.h

@@ -187,7 +187,7 @@ class RISCVSubtarget : public RISCVGenSubtargetInfo {
   }
 
   bool hasCLZLike() const {
-    return HasStdExtZbb || HasVendorXTHeadBb ||
+    return HasStdExtZbb || HasStdExtP || HasVendorXTHeadBb ||
            (HasVendorXCVbitmanip && !IsRV64);
   }
   bool hasCTZLike() const {
@@ -197,7 +197,7 @@ class RISCVSubtarget : public RISCVGenSubtargetInfo {
     return HasStdExtZbb || (HasVendorXCVbitmanip && !IsRV64);
   }
   bool hasREV8Like() const {
-    return HasStdExtZbb || HasStdExtZbkb || HasVendorXTHeadBb;
+    return HasStdExtZbb || HasStdExtZbkb || HasStdExtP || HasVendorXTHeadBb;
   }
 
   bool hasBEXTILike() const { return HasStdExtZbs || HasVendorXTHeadBs; }