[RISCV] Emit .variant_cc directives for vector function calls.

The patch is splitted from D103435. The patch emits .variant_cc [0] for those
function calls that have vector arguments or vector return values.

[0]: riscv-non-isa/riscv-elf-psabi-doc#190

Initial authored by: HsiangKai

Reviewed By: reames

Differential Revision: https://reviews.llvm.org/D139414

Author: Yeting Kuo

llvm/lib/Target/RISCV/MCTargetDesc/RISCVTargetStreamer.cpp

@@ -13,6 +13,7 @@
 #include "RISCVTargetStreamer.h"
 #include "RISCVBaseInfo.h"
 #include "RISCVMCTargetDesc.h"
+#include "llvm/MC/MCSymbol.h"
 #include "llvm/Support/FormattedStream.h"
 #include "llvm/Support/RISCVAttributes.h"
 #include "llvm/Support/RISCVISAInfo.h"
@@ -98,6 +99,10 @@ void RISCVTargetAsmStreamer::emitDirectiveOptionNoRelax() {
   OS << "\t.option\tnorelax\n";
 }
 
+void RISCVTargetAsmStreamer::emitDirectiveVariantCC(MCSymbol &Symbol) {
+  OS << "\t.variant_cc\t" << Symbol.getName() << "\n";
+}
+
 void RISCVTargetAsmStreamer::emitAttribute(unsigned Attribute, unsigned Value) {
   OS << "\t.attribute\t" << Attribute << ", " << Twine(Value) << "\n";
 }

llvm/lib/Target/RISCV/MCTargetDesc/RISCVTargetStreamer.h

@@ -66,6 +66,7 @@ class RISCVTargetAsmStreamer : public RISCVTargetStreamer {
   void emitDirectiveOptionNoRVC() override;
   void emitDirectiveOptionRelax() override;
   void emitDirectiveOptionNoRelax() override;
+  void emitDirectiveVariantCC(MCSymbol &Symbol) override;
 };
 
 }

llvm/lib/Target/RISCV/RISCVAsmPrinter.cpp

@@ -15,6 +15,7 @@
 #include "MCTargetDesc/RISCVMCExpr.h"
 #include "MCTargetDesc/RISCVTargetStreamer.h"
 #include "RISCV.h"
+#include "RISCVMachineFunctionInfo.h"
 #include "RISCVTargetMachine.h"
 #include "TargetInfo/RISCVTargetInfo.h"
 #include "llvm/ADT/Statistic.h"
@@ -81,6 +82,8 @@ class RISCVAsmPrinter : public AsmPrinter {
   void emitStartOfAsmFile(Module &M) override;
   void emitEndOfAsmFile(Module &M) override;
 
+  void emitFunctionEntryLabel() override;
+
 private:
   void emitAttributes();
 };
@@ -225,6 +228,16 @@ void RISCVAsmPrinter::emitAttributes() {
   RTS.emitTargetAttributes(*MCSTI);
 }
 
+void RISCVAsmPrinter::emitFunctionEntryLabel() {
+  const auto *RMFI = MF->getInfo<RISCVMachineFunctionInfo>();
+  if (RMFI->isVectorCall()) {
+    auto &RTS =
+        static_cast<RISCVTargetStreamer &>(*OutStreamer->getTargetStreamer());
+    RTS.emitDirectiveVariantCC(*CurrentFnSym);
+  }
+  return AsmPrinter::emitFunctionEntryLabel();
+}
+
 // Force static initialization.
 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeRISCVAsmPrinter() {
   RegisterAsmPrinter<RISCVAsmPrinter> X(getTheRISCV32Target());

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -12070,6 +12070,10 @@ SDValue RISCVTargetLowering::LowerFormalArguments(
     InVals.push_back(ArgValue);
   }
 
+  if (any_of(ArgLocs,
+             [](CCValAssign &VA) { return VA.getLocVT().isScalableVector(); }))
+    MF.getInfo<RISCVMachineFunctionInfo>()->setIsVectorCall();
+
   if (IsVarArg) {
     ArrayRef<MCPhysReg> ArgRegs = makeArrayRef(ArgGPRs);
     unsigned Idx = CCInfo.getFirstUnallocated(ArgRegs);
@@ -12540,7 +12544,7 @@ RISCVTargetLowering::LowerReturn(SDValue Chain, CallingConv::ID CallConv,
                                  const SmallVectorImpl<ISD::OutputArg> &Outs,
                                  const SmallVectorImpl<SDValue> &OutVals,
                                  const SDLoc &DL, SelectionDAG &DAG) const {
-  const MachineFunction &MF = DAG.getMachineFunction();
+  MachineFunction &MF = DAG.getMachineFunction();
   const RISCVSubtarget &STI = MF.getSubtarget<RISCVSubtarget>();
 
   // Stores the assignment of the return value to a location.
@@ -12611,6 +12615,10 @@ RISCVTargetLowering::LowerReturn(SDValue Chain, CallingConv::ID CallConv,
     RetOps.push_back(Glue);
   }
 
+  if (any_of(RVLocs,
+             [](CCValAssign &VA) { return VA.getLocVT().isScalableVector(); }))
+    MF.getInfo<RISCVMachineFunctionInfo>()->setIsVectorCall();
+
   unsigned RetOpc = RISCVISD::RET_FLAG;
   // Interrupt service routines use different return instructions.
   const Function &Func = DAG.getMachineFunction().getFunction();

llvm/lib/Target/RISCV/RISCVMachineFunctionInfo.h

@@ -65,6 +65,8 @@ class RISCVMachineFunctionInfo : public MachineFunctionInfo {
   uint64_t RVVPadding = 0;
   /// Size of stack frame to save callee saved registers
   unsigned CalleeSavedStackSize = 0;
+  /// Is there any vector argument or return?
+  bool IsVectorCall = false;
 
   /// Registers that have been sign extended from i32.
   SmallVector<Register, 8> SExt32Registers;
@@ -124,6 +126,9 @@ class RISCVMachineFunctionInfo : public MachineFunctionInfo {
 
   void addSExt32Register(Register Reg);
   bool isSExt32Register(Register Reg) const;
+
+  bool isVectorCall() const { return IsVectorCall; }
+  void setIsVectorCall() { IsVectorCall = true; }
 };
 
 } // end namespace llvm

llvm/test/CodeGen/RISCV/rvv/variant-cc.ll

@@ -0,0 +1,51 @@
+; RUN: llc -mtriple=riscv64 -mattr=+v -o - %s | FileCheck %s --check-prefix=CHECK-ASM
+; RUN: llc -mtriple=riscv64 -mattr=+v -filetype=obj -o - %s \
+; RUN:   | llvm-readobj --symbols - | FileCheck %s --check-prefix=CHECK-OBJ
+
+define i32 @base_cc() {
+; CHECK-ASM-LABEL: base_cc:
+; CHECK-ASM-NOT: .variant_cc
+; CHECK-OBJ-LABEL: Name: base_cc
+; CHECK-OBJ: Other: 0
+  ret i32 42
+}
+
+define <4 x i32> @fixed_vector_cc_1(<4 x i32> %arg) {
+; CHECK-ASM: .variant_cc fixed_vector_cc_1
+; CHECK-ASM-NEXT: fixed_vector_cc_1:
+; CHECK-OBJ-LABEL: Name: fixed_vector_cc_1
+; CHECK-OBJ: Other [ (0x80)
+  ret <4 x i32> %arg
+}
+
+define <vscale x 4 x i32> @rvv_vector_cc_1() {
+; CHECK-ASM: .variant_cc rvv_vector_cc_1
+; CHECK-ASM-NEXT: rvv_vector_cc_1:
+; CHECK-OBJ-LABEL: Name: rvv_vector_cc_1
+; CHECK-OBJ: Other [ (0x80)
+  ret <vscale x 4 x i32> undef
+}
+
+define <vscale x 4 x i1> @rvv_vector_cc_2() {
+; CHECK-ASM: .variant_cc rvv_vector_cc_2
+; CHECK-ASM-NEXT: rvv_vector_cc_2:
+; CHECK-OBJ-LABEL: Name: rvv_vector_cc_2
+; CHECK-OBJ: Other [ (0x80)
+  ret <vscale x 4 x i1> undef
+}
+
+define void @rvv_vector_cc_3(<vscale x 4 x i32> %arg) {
+; CHECK-ASM: .variant_cc rvv_vector_cc_3
+; CHECK-ASM-NEXT: rvv_vector_cc_3:
+; CHECK-OBJ-LABEL: Name: rvv_vector_cc_3
+; CHECK-OBJ: Other [ (0x80)
+  ret void
+}
+
+define void @rvv_vector_cc_4(<vscale x 4 x i1> %arg) {
+; CHECK-ASM: .variant_cc rvv_vector_cc_4
+; CHECK-ASM-NEXT: rvv_vector_cc_4:
+; CHECK-OBJ-LABEL: Name: rvv_vector_cc_4
+; CHECK-OBJ: Other [ (0x80)
+  ret void
+}