[RISCV] RISCV vector calling convention (1/2) (#77560)

    [RISCV] RISCV vector calling convention (1/2)

    This is the vector calling convention based on
    https://github.com/riscv-non-isa/riscv-elf-psabi-doc,
    the idea is to split between "scalar" callee-saved registers
    and "vector" callee-saved registers. "scalar" ones remain the
    original strategy, however, "vector" ones are handled together
    with RVV objects.

    The stack layout would be:

      |--------------------------| <-- FP
      | callee-allocated save    |
      | area for register varargs|
      |--------------------------|
      | callee-saved registers   | <-- scalar callee-saved
      |        (scalar)          |
      |--------------------------|
      | RVV alignment padding    |
      |--------------------------|
      | callee-saved registers   | <-- vector callee-saved
      |        (vector)          |
      |--------------------------|
      | RVV objects              |
      |--------------------------|
      | padding before RVV       |
      |--------------------------|
      | scalar local variables   |
      |--------------------------| <-- BP
      | variable size objects    |
      |--------------------------| <-- SP

    Note: This patch doesn't contain "tuple" type, e.g. vint32m1x2.
          It will be handled in https://github.com/riscv-non-isa/riscv-elf-psabi-doc (2/2).

    Differential Revision: https://reviews.llvm.org/D154576

1 files changed, 6 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 475d96b..b8adf5c 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -74,6 +74,9 @@ unsigned CodeGenTypes::ClangCallConvToLLVMCallConv(CallingConv CC) {
   case CC_SwiftAsync: return llvm::CallingConv::SwiftTail;
   case CC_M68kRTD: return llvm::CallingConv::M68k_RTD;
   case CC_PreserveNone: return llvm::CallingConv::PreserveNone;
+    // clang-format off
+  case CC_RISCVVectorCall: return llvm::CallingConv::RISCV_VectorCall;
+    // clang-format on
   }
 }
 
@@ -260,6 +263,9 @@ static CallingConv getCallingConventionForDecl(const ObjCMethodDecl *D,
   if (D->hasAttr<PreserveNoneAttr>())
     return CC_PreserveNone;
 
+  if (D->hasAttr<RISCVVectorCCAttr>())
+    return CC_RISCVVectorCall;
+
   return CC_C;
 }