[RISCV][VCIX] Add vcix_state to GNU inline assembly register set (#106914)

riscv-non-isa/riscv-toolchain-conventions#56
Resolved #106700.
This enables inline asm to have vcix_state to be a clobbered register
thus disable reordering between VCIX intrinsics and inline asm.

Author: 4vtomat

clang/lib/Basic/Targets/RISCV.cpp

@@ -44,7 +44,7 @@ ArrayRef<const char *> RISCVTargetInfo::getGCCRegNames() const {
       "v24", "v25", "v26", "v27", "v28", "v29", "v30", "v31",
 
       // CSRs
-      "fflags", "frm", "vtype", "vl", "vxsat", "vxrm"
+      "fflags", "frm", "vtype", "vl", "vxsat", "vxrm", "sf.vcix_state"
     };
   // clang-format on
   return llvm::ArrayRef(GCCRegNames);

llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp

@@ -715,6 +715,12 @@ Register RISCVRegisterInfo::getFrameRegister(const MachineFunction &MF) const {
   return TFI->hasFP(MF) ? RISCV::X8 : RISCV::X2;
 }
 
+StringRef RISCVRegisterInfo::getRegAsmName(MCRegister Reg) const {
+  if (Reg == RISCV::SF_VCIX_STATE)
+    return "sf.vcix_state";
+  return TargetRegisterInfo::getRegAsmName(Reg);
+}
+
 const uint32_t *
 RISCVRegisterInfo::getCallPreservedMask(const MachineFunction & MF,
                                         CallingConv::ID CC) const {

llvm/lib/Target/RISCV/RISCVRegisterInfo.h

@@ -102,6 +102,8 @@ struct RISCVRegisterInfo : public RISCVGenRegisterInfo {
 
   Register getFrameRegister(const MachineFunction &MF) const override;
 
+  StringRef getRegAsmName(MCRegister Reg) const override;
+
   bool requiresRegisterScavenging(const MachineFunction &MF) const override {
     return true;
   }

llvm/lib/Target/RISCV/RISCVRegisterInfo.td

@@ -717,3 +717,7 @@ def SSP    : RISCVReg<0, "ssp">;
 
 // Dummy SiFive VCIX state register
 def SF_VCIX_STATE : RISCVReg<0, "sf.vcix_state">;
+def : RISCVRegisterClass<[XLenVT], 32, (add SF_VCIX_STATE)> {
+  let RegInfos = XLenRI;
+  let isAllocatable = 0;
+}

llvm/test/CodeGen/RISCV/inline-asm-xsfvcp.ll

@@ -0,0 +1,22 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: sed 's/iXLen/i32/g' %s | llc -mtriple=riscv32 -mattr=+v,+xsfvcp \
+; RUN:   -verify-machineinstrs | FileCheck %s --check-prefixes=CHECK
+; RUN: sed 's/iXLen/i64/g' %s | llc -mtriple=riscv64 -mattr=+v,+xsfvcp \
+; RUN:   -verify-machineinstrs | FileCheck %s --check-prefixes=CHECK
+
+; VCIX instructions can not reorder between each other.
+define void @test_reorder(<vscale x 1 x i64> %vreg) {
+; CHECK-LABEL: test_reorder:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetivli zero, 0, e64, m1, ta, ma
+; CHECK-NEXT:    sf.vc.iv 0, 0, v8, 0
+; CHECK-NEXT:    #APP
+; CHECK-NEXT:    sf.vc.vv 3, 0, v8, v8
+; CHECK-EMPTY:
+; CHECK-NEXT:    #NO_APP
+; CHECK-NEXT:    ret
+entry:
+  call void @llvm.riscv.sf.vc.iv.se.iXLen.nxv1i64.iXLen.iXLen(iXLen 0, iXLen 0, <vscale x 1 x i64> %vreg, iXLen 0, iXLen 0)
+  call iXLen asm sideeffect "sf.vc.vv 0x3, 0x0, $1, $1;", "=r,^vr,~{memory},~{vl},~{sf.vcix_state}"(<vscale x 1 x i64> %vreg)
+  ret void
+}