Target ABI: improve call parameters extensions handling (#100757)

For the purpose of verifying proper arguments extensions per the target's ABI,
introduce the NoExt attribute that may be used by a target when neither sign-
or zeroextension is required (e.g. with a struct in register). The purpose of
doing so is to be able to verify that there is always one of these attributes
present and by this detecting cases where sign/zero extension is actually
missing.

As a first step, this patch has the verification step done for the SystemZ
backend only, but left off by default until all known issues have been
addressed.

Other targets/front-ends can now also add NoExt attribute where needed and do
this check in the backend.

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 027a297..b7db631 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -2190,6 +2190,8 @@ static Attribute::AttrKind getAttrFromCode(uint64_t Code) {
     return Attribute::Initializes;
   case bitc::ATTR_KIND_CORO_ELIDE_SAFE:
     return Attribute::CoroElideSafe;
+  case bitc::ATTR_KIND_NO_EXT:
+    return Attribute::NoExt;
   }
 }