LowerTypeTests: When importing functions skip definitions where the summary contains a decl.

[pcc]

Summary

This normally indicates mixed CFI + non-CFI compilation, and will
result in us treating the function in the same way as a function
defined outside of the LTO unit.

Part of PR33752.

[eugenis]

Thank you!

llvm/trunk/lib/Transforms/IPO/LowerTypeTests.cpp

void LowerTypeTestsModule::importFunction(Function *F, bool isDefinition) {
   std::string Name = F->getName();
   Function *FDecl;
 
   if (F->isDeclarationForLinker() && !isDefinition) {
     // Declaration of an external function.
     FDecl = Function::Create(F->getFunctionType(), GlobalValue::ExternalLinkage,
                              Name + ".cfi_jt", &M);
     FDecl->setVisibility(GlobalValue::HiddenVisibility);
-  } else {
-    // Definition.
-    assert(isDefinition);
+  } else if (isDefinition) {
     F->setName(Name + ".cfi");
     F->setLinkage(GlobalValue::ExternalLinkage);
     F->setVisibility(GlobalValue::HiddenVisibility);
     FDecl = Function::Create(F->getFunctionType(), GlobalValue::ExternalLinkage,
                              Name, &M);
     FDecl->setVisibility(Visibility);
+  } else {
+    // Function definition without type metadata, where some other translation
+    // unit contained a declaration with type metadata. This normally happens
+    // during mixed CFI + non-CFI compilation. We do nothing with the function
+    // so that it is treated the same way as a function defined outside of the
+    // LTO unit.
+    return;
   }
 
   if (F->isWeakForLinker())
     replaceWeakDeclarationWithJumpTablePtr(F, FDecl);
   else
     F->replaceAllUsesWith(FDecl);
 }
 

llvm/trunk/test/Transforms/LowerTypeTests/Inputs/import-icall.yaml

 WithGlobalValueDeadStripping: false
 CfiFunctionDefs:
   - local_a
   - local_b
   - does_not_exist
 CfiFunctionDecls:
   - external
   - external_weak
+  - local_decl
 ...

llvm/trunk/test/Transforms/LowerTypeTests/import-icall.ll

define internal i8 @local_b() {
   ret i8 %x
 }
 
 define i8 @use_b() {
   %x = call i8 @local_b()
   ret i8 %x
 }
 
+define void @local_decl() {
+  call void @local_decl()
+  ret void
+}
 
 declare void @external()
 declare extern_weak void @external_weak()
 
 ; CHECK:      define hidden i8 @local_a.cfi() {
 ; CHECK-NEXT:   call void @external.cfi_jt()
 ; CHECK-NEXT:   call void select (i1 icmp ne (void ()* @external_weak, void ()* null), void ()* @external_weak.cfi_jt, void ()* null)()
 ; CHECK-NEXT:   ret i8 1
 ; CHECK-NEXT: }
 
 ; internal @local_b is not the same function as "local_b" in the summary.
 ; CHECK:      define internal i8 @local_b() {
 ; CHECK-NEXT:   call i8 @local_a()
 
+; CHECK:      define void @local_decl()
+; CHECK-NEXT:   call void @local_decl()
+
 ; CHECK: declare void @external()
 ; CHECK: declare extern_weak void @external_weak()
 ; CHECK: declare i8 @local_a()
 ; CHECK: declare hidden void @external.cfi_jt()
 ; CHECK: declare hidden void @external_weak.cfi_jt()