[llvm] [CHERI] Add enum values and LL parse/print support for CHERI calling conventions. (PR #156328)

[Owen Anderson via llvm-commits]

https://github.com/resistor created https://github.com/llvm/llvm-project/pull/156328

This is the union of the calling conventions supported by the CTSRD and CHERIoT CHERI downstreams of LLVM.


>From 6b074157f964940b4082c720ef7ad9c25588facc Mon Sep 17 00:00:00 2001
From: Owen Anderson <resistor at mac.com>
Date: Mon, 1 Sep 2025 21:27:39 +0800
Subject: [PATCH] [CHERI] Add enum values and LL parse/print support for CHERI
 calling conventions.

This is the union of the calling conventions supported by the CTSRD and CHERIoT CHERI downstreams of LLVM.
---
 llvm/include/llvm/AsmParser/LLToken.h |  3 +++
 llvm/include/llvm/IR/CallingConv.h    | 11 +++++++++++
 llvm/lib/AsmParser/LLLexer.cpp        |  3 +++
 llvm/lib/AsmParser/LLParser.cpp       |  3 +++
 llvm/lib/IR/AsmWriter.cpp             |  3 +++
 5 files changed, 23 insertions(+)

diff --git a/llvm/include/llvm/AsmParser/LLToken.h b/llvm/include/llvm/AsmParser/LLToken.h
index e6a0eae9da30c..b5b6bff6a27b7 100644
--- a/llvm/include/llvm/AsmParser/LLToken.h
+++ b/llvm/include/llvm/AsmParser/LLToken.h
@@ -187,6 +187,9 @@ enum Kind {
   kw_graalcc,
   kw_riscv_vector_cc,
   kw_riscv_vls_cc,
+  kw_chericcallcc,
+  kw_chericcallee,
+  kw_cherilibcallcc,
 
   // Attributes:
   kw_attributes,
diff --git a/llvm/include/llvm/IR/CallingConv.h b/llvm/include/llvm/IR/CallingConv.h
index ef761eb1aed73..c89ffafd3a1c8 100644
--- a/llvm/include/llvm/IR/CallingConv.h
+++ b/llvm/include/llvm/IR/CallingConv.h
@@ -287,6 +287,17 @@ namespace CallingConv {
     // Calling convention for AMDGPU whole wave functions.
     AMDGPU_Gfx_WholeWave = 124,
 
+    /// CHERI_CCall - Calling convention used for CHERI when crossing a
+    /// protection boundary.
+    CHERI_CCall = 125,
+    /// CHERI_CCallee - Calling convention used for the callee of CHERI_CCall.
+    /// Ignores the first two capability arguments and the first integer
+    /// argument, zeroes all unused return registers on return.
+    CHERI_CCallee = 126,
+    /// CHERI_LibCall - Calling convention used for cross-library calls to a
+    /// stateless compartment.
+    CHERI_LibCall = 127,
+
     /// The highest possible ID. Must be some 2^k - 1.
     MaxID = 1023
   };
diff --git a/llvm/lib/AsmParser/LLLexer.cpp b/llvm/lib/AsmParser/LLLexer.cpp
index 3d5bd6155536e..8a36df86af21a 100644
--- a/llvm/lib/AsmParser/LLLexer.cpp
+++ b/llvm/lib/AsmParser/LLLexer.cpp
@@ -685,6 +685,9 @@ lltok::Kind LLLexer::LexIdentifier() {
   KEYWORD(graalcc);
   KEYWORD(riscv_vector_cc);
   KEYWORD(riscv_vls_cc);
+  KEYWORD(chericcallcc)
+  KEYWORD(chericcallee)
+  KEYWORD(cherilibcallcc)
 
   KEYWORD(cc);
   KEYWORD(c);
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 1bc2906f63b07..2374b97a453cb 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -2312,6 +2312,9 @@ bool LLParser::parseOptionalCallingConv(unsigned &CC) {
 #undef CC_VLS_CASE
     }
     return false;
+  case lltok::kw_chericcallcc:        CC = CallingConv::CHERI_CCall; break;
+  case lltok::kw_chericcallee:        CC = CallingConv::CHERI_CCallee; break;
+  case lltok::kw_cherilibcallcc:      CC = CallingConv::CHERI_LibCall; break;
   case lltok::kw_cc: {
       Lex.Lex();
       return parseUInt32(CC);
diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index dc6d599fa9585..38e302f00ea1f 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -428,6 +428,9 @@ static void PrintCallingConv(unsigned cc, raw_ostream &Out) {
     CC_VLS_CASE(32768)
     CC_VLS_CASE(65536)
 #undef CC_VLS_CASE
+  case CallingConv::CHERI_CCall:   Out << "chericcallcc"; break;
+  case CallingConv::CHERI_CCallee: Out << "chericcallee"; break;
+  case CallingConv::CHERI_LibCall: Out << "cherilibcallcc"; break;
   }
 }