[Xtensa] Implement CTLZ/CTTZ with NSAU

Close espressif#77

Author: zRedShift

llvm/lib/Target/Xtensa/XtensaISelLowering.cpp

@@ -201,10 +201,12 @@ XtensaTargetLowering::XtensaTargetLowering(const TargetMachine &tm,
   setOperationAction(ISD::ROTL, MVT::i32, Expand);
   setOperationAction(ISD::ROTR, MVT::i32, Expand);
   setOperationAction(ISD::CTPOP, MVT::i32, Expand);
-  setOperationAction(ISD::CTTZ, MVT::i32, Expand);
-  setOperationAction(ISD::CTLZ, MVT::i32, Expand);
-  setOperationAction(ISD::CTTZ_ZERO_UNDEF, MVT::i32, Expand);
-  setOperationAction(ISD::CTLZ_ZERO_UNDEF, MVT::i32, Expand);
+  setOperationAction({ISD::CTTZ, ISD::CTTZ_ZERO_UNDEF}, MVT::i32, Expand);
+  if (Subtarget.hasNSA())
+    setOperationAction(ISD::CTLZ, MVT::i32, Legal);
+  else
+    setOperationAction({ISD::CTLZ, ISD::CTLZ_ZERO_UNDEF}, MVT::i32, Expand);
+
 
   setOperationAction({ISD::SMIN, ISD::SMAX, ISD::UMIN, ISD::UMAX},
                      MVT::i32, Subtarget.hasMINMAX() ? Legal : Expand);
@@ -409,6 +411,18 @@ bool XtensaTargetLowering::isFMAFasterThanFMulAndFAdd(const MachineFunction &MF,
   return false;
 }
 
+bool XtensaTargetLowering::isCheapToSpeculateCtlz(Type *) const {
+  return Subtarget.hasNSA();
+}
+
+bool XtensaTargetLowering::isCheapToSpeculateCttz(Type *) const {
+  return Subtarget.hasNSA();
+}
+
+bool XtensaTargetLowering::isCtlzFast() const {
+  return Subtarget.hasNSA();
+}
+
 /// If a physical register, this returns the register that receives the
 /// exception address on entry to an EH pad.
 Register XtensaTargetLowering::getExceptionPointerRegister(

llvm/lib/Target/Xtensa/XtensaISelLowering.h

@@ -121,6 +121,11 @@ class XtensaTargetLowering : public TargetLowering {
                                   EVT VT) const override;
 
   bool isFNegFree(EVT VT) const override;
+  bool isCheapToSpeculateCtlz(Type *Ty) const override;
+
+  bool isCheapToSpeculateCttz(Type *Ty) const override;
+
+  bool isCtlzFast() const override;
 
   /// If a physical register, this returns the register that receives the
   /// exception address on entry to an EH pad.

llvm/lib/Target/Xtensa/XtensaInstrInfo.td

@@ -1362,7 +1362,8 @@ def NSA : RRR_Inst<0x00, 0x00, 0x04, (outs AR:$t), (ins AR:$s),
 }
 
 def NSAU : RRR_Inst<0x00, 0x00, 0x04, (outs AR:$t), (ins AR:$s),
-                   "nsau\t$t, $s", []>, Requires<[HasNSA]> {
+                   "nsau\t$t, $s",
+                   [(set AR:$t, (ctlz AR:$s))]>, Requires<[HasNSA]> {
   let r = 0xF;
 }
 

llvm/test/CodeGen/Xtensa/ctlz-cttz.ll

@@ -0,0 +1,67 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=xtensa -mcpu=esp32 -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=XTENSA %s
+
+declare i32 @llvm.ctlz.i32(i32, i1)
+
+define i32 @test1_ctlz(i32 %v) {
+; XTENSA-LABEL: test1_ctlz:
+; XTENSA:       # %bb.0:
+; XTENSA-NEXT:    entry a1, 32
+; XTENSA-NEXT:    .cfi_def_cfa_offset 32
+; XTENSA-NEXT:    nsau a2, a2
+; XTENSA-NEXT:    retw.n
+  %1 = tail call i32 @llvm.ctlz.i32(i32 %v, i1 false)
+  ret i32 %1
+}
+
+define i32 @test2_ctlz(i32 %v) {
+; XTENSA-LABEL: test2_ctlz:
+; XTENSA:       # %bb.0:
+; XTENSA-NEXT:    entry a1, 32
+; XTENSA-NEXT:    .cfi_def_cfa_offset 32
+; XTENSA-NEXT:    nsau a2, a2
+; XTENSA-NEXT:    retw.n
+  %cnt = tail call i32 @llvm.ctlz.i32(i32 %v, i1 true)
+  %tobool = icmp eq i32 %v, 0
+  %cond = select i1 %tobool, i32 32, i32 %cnt
+  ret i32 %cond
+}
+
+declare i32 @llvm.cttz.i32(i32, i1)
+
+define i32 @test1_cttz(i32 %v) {
+; XTENSA-LABEL: test1_cttz:
+; XTENSA:       # %bb.0:
+; XTENSA-NEXT:    entry a1, 32
+; XTENSA-NEXT:    .cfi_def_cfa_offset 32
+; XTENSA-NEXT:    movi.n a8, -1
+; XTENSA-NEXT:    xor a8, a2, a8
+; XTENSA-NEXT:    addi.n a9, a2, -1
+; XTENSA-NEXT:    and a8, a8, a9
+; XTENSA-NEXT:    nsau a8, a8
+; XTENSA-NEXT:    movi.n a9, 32
+; XTENSA-NEXT:    sub a2, a9, a8
+; XTENSA-NEXT:    retw.n
+  %1 = tail call i32 @llvm.cttz.i32(i32 %v, i1 false)
+  ret i32 %1
+}
+
+define i32 @test2_cttz(i32 %v) {
+; XTENSA-LABEL: test2_cttz:
+; XTENSA:       # %bb.0:
+; XTENSA-NEXT:    entry a1, 32
+; XTENSA-NEXT:    .cfi_def_cfa_offset 32
+; XTENSA-NEXT:    movi.n a8, -1
+; XTENSA-NEXT:    xor a8, a2, a8
+; XTENSA-NEXT:    addi.n a9, a2, -1
+; XTENSA-NEXT:    and a8, a8, a9
+; XTENSA-NEXT:    nsau a8, a8
+; XTENSA-NEXT:    movi.n a9, 32
+; XTENSA-NEXT:    sub a2, a9, a8
+; XTENSA-NEXT:    retw.n
+  %cnt = tail call i32 @llvm.cttz.i32(i32 %v, i1 true)
+  %tobool = icmp eq i32 %v, 0
+  %cond = select i1 %tobool, i32 32, i32 %cnt
+  ret i32 %cond
+}

llvm/test/MC/Xtensa/xtensa-valid-nsa.s

@@ -0,0 +1,12 @@
+# RUN: llvm-mc %s -triple=xtensa -mattr=+nsa -show-encoding \
+# RUN:     | FileCheck -check-prefixes=CHECK,CHECK-INST %s
+
+# Instruction format RRR
+# CHECK-INST: nsa a3, a2
+# CHECK: encoding: [0x30,0xe2,0x40]
+nsa a3, a2
+
+# Instruction format RRR
+# CHECK-INST: nsau a3, a2
+# CHECK: encoding: [0x30,0xf2,0x40]
+nsau a3, a2