[Clang][C++23] Implement P1774R8: Portable assumptions (#81014)

This implements the C++23 `[[assume]]` attribute.

Assumption information is lowered to a call to `@llvm.assume`, unless the expression has side-effects, in which case it is discarded and a warning is issued to tell the user that the assumption doesn’t do anything. A failed assumption at compile time is an error (unless we are in `MSVCCompat` mode, in which case we don’t check assumptions at compile time).

Due to performance regressions in LLVM, assumptions can be disabled with the `-fno-assumptions` flag. With it, assumptions will still be parsed and checked, but no calls to `@llvm.assume` will be emitted and assumptions will not be checked at compile time.

1 files changed, 4 insertions, 4 deletions

diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 13f6823..a28d788 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -1796,14 +1796,14 @@ static void AddAttributesFromFunctionProtoType(ASTContext &Ctx,
     FuncAttrs.addAttribute("aarch64_inout_zt0");
 }
 
-static void AddAttributesFromAssumes(llvm::AttrBuilder &FuncAttrs,
-                                     const Decl *Callee) {
+static void AddAttributesFromOMPAssumes(llvm::AttrBuilder &FuncAttrs,
+                                        const Decl *Callee) {
   if (!Callee)
     return;
 
   SmallVector<StringRef, 4> Attrs;
 
-  for (const AssumptionAttr *AA : Callee->specific_attrs<AssumptionAttr>())
+  for (const OMPAssumeAttr *AA : Callee->specific_attrs<OMPAssumeAttr>())
     AA->getAssumption().split(Attrs, ",");
 
   if (!Attrs.empty())
@@ -2344,7 +2344,7 @@ void CodeGenModule::ConstructAttributeList(StringRef Name,
 
   // Attach assumption attributes to the declaration. If this is a call
   // site, attach assumptions from the caller to the call as well.
-  AddAttributesFromAssumes(FuncAttrs, TargetDecl);
+  AddAttributesFromOMPAssumes(FuncAttrs, TargetDecl);
 
   bool HasOptnone = false;
   // The NoBuiltinAttr attached to the target FunctionDecl.