[llvm-branch-commits] [clang] [CIR] Implement Direct+canFlatten in CallConvLowering (PR #201719)

[via llvm-branch-commits]

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@@ -61,11 +88,20 @@ LogicalResult buildNewArgTypes(ArrayRef<Type> oldArgTypes,
     Type origTy = oldArgTypes[idx];
     switch (ac.kind) {
     case ArgKind::Direct:
-      // Direct with a coerced type means the wire signature uses the
-      // coerced type; the body still expects origTy and we'll insert a
-      // coercion at the entry block.  Direct without a coerced type is a
-      // true pass-through.
-      newArgTypes.push_back(ac.coercedType ? ac.coercedType : origTy);
+      // Direct with canFlatten and a struct coerced type: push one wire type
+      // per field of the coerced struct rather than the struct itself.
+      // Single-field coerced structs fall through to the non-flatten path —
+      // the struct is already scalar-sized and flattening adds no value.
+      if (auto flatTy = getFlattenedCoercedType(ac)) {
+        for (Type memberTy : flatTy.getMembers())
+          newArgTypes.push_back(memberTy);
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adams381 wrote:

Switched to `llvm::append_range(newArgTypes, flatTy.getMembers())`.


https://github.com/llvm/llvm-project/pull/201719