[PATCH] D35604: LowerTypeTests: Drop function type metadata only if we're going to replace it.

[Peter Collingbourne via Phabricator via llvm-commits]

pcc created this revision.
Herald added subscribers: hiraditya, mehdi_amini.

Previously we were (mis)handling jump table members with a prevailing
definition in a full LTO module and a non-prevailing definition in a
ThinLTO module by dropping type metadata on those functions entirely,
which would cause type tests involving such functions to fail.

This patch causes us to drop metadata only if we are about to replace
it with metadata from cfi.functions.

We also want to replace metadata for available_externally functions,
which can arise in the opposite scenario (prevailing ThinLTO
definition, non-prevailing full LTO definition). The simplest way
to handle that is to remove the definition; there's little value in
keeping it around at this point (i.e. after most optimization passes
have already run) and later code will try to use the function's linkage
to create an alias, which would result in invalid IR if the function
is available_externally.

Fixes PR33832.


https://reviews.llvm.org/D35604

Files:
  llvm/lib/Transforms/IPO/LowerTypeTests.cpp
  llvm/test/Transforms/LowerTypeTests/export-icall.ll


Index: llvm/test/Transforms/LowerTypeTests/export-icall.ll
===================================================================
--- llvm/test/Transforms/LowerTypeTests/export-icall.ll
+++ llvm/test/Transforms/LowerTypeTests/export-icall.ll
@@ -9,18 +9,22 @@
 }
 
 declare !type !8 void @f(i32 %x)
+define available_externally void @f2(i32 %x) !type !8 {
+  ret void
+}
 
-!cfi.functions = !{!0, !1, !3, !4, !5, !6}
+!cfi.functions = !{!0, !1, !3, !9, !4, !5, !6}
 
 ; declaration of @h with a different type is ignored
 !0 = !{!"h", i8 1, !7}
 
 ; extern_weak declaration of @h with a different type is ignored as well
 !1 = !{!"h", i8 2, !8}
 !2 = !{i64 0, !"typeid1"}
 
-; definition of @f replaces types on the IR declaration above
+; definitions of @f and @f2 replace types on the IR declarations above
 !3 = !{!"f", i8 0, !2}
+!9 = !{!"f2", i8 0, !2}
 !4 = !{!"external", i8 1, !2}
 !5 = !{!"external_weak", i8 2, !2}
 !6 = !{!"g", i8 0, !7}
@@ -30,10 +34,11 @@
 
 ; CHECK-DAG: @__typeid_typeid1_global_addr = hidden alias i8, bitcast (void ()* [[JT1:.*]] to i8*)
 ; CHECK-DAG: @__typeid_typeid1_align = hidden alias i8, inttoptr (i8 3 to i8*)
-; CHECK-DAG: @__typeid_typeid1_size_m1 = hidden alias i8, inttoptr (i64 3 to i8*)
+; CHECK-DAG: @__typeid_typeid1_size_m1 = hidden alias i8, inttoptr (i64 4 to i8*)
 
 ; CHECK-DAG: @h                    = alias void (i8), bitcast (void ()* [[JT1]] to void (i8)*)
 ; CHECK-DAG: @f                    = alias void (i32), {{.*}}getelementptr {{.*}}void ()* [[JT1]]
+; CHECK-DAG: @f2                   = alias void (i32), {{.*}}getelementptr {{.*}}void ()* [[JT1]]
 ; CHECK-DAG: @external.cfi_jt      = hidden alias void (), {{.*}}getelementptr {{.*}}void ()* [[JT1]]
 ; CHECK-DAG: @external_weak.cfi_jt = hidden alias void (), {{.*}}getelementptr {{.*}}void ()* [[JT1]]
 
@@ -45,6 +50,7 @@
 ; CHECK-DAG: declare !type !{{.*}} void @external()
 ; CHECK-DAG: declare !type !{{.*}} void @external_weak()
 ; CHECK-DAG: declare !type !{{.*}} void @f.cfi(i32)
+; CHECK-DAG: declare !type !{{.*}} void @f2.cfi(i32)
 ; CHECK-DAG: declare !type !{{.*}} void @g.cfi()
 
 
@@ -62,6 +68,7 @@
 
 ; SUMMARY:      CfiFunctionDefs:
 ; SUMMARY-NEXT:   - f
+; SUMMARY-NEXT:   - f2
 ; SUMMARY-NEXT:   - g
 ; SUMMARY-NEXT:   - h
 ; SUMMARY-NEXT: CfiFunctionDecls:
Index: llvm/lib/Transforms/IPO/LowerTypeTests.cpp
===================================================================
--- llvm/lib/Transforms/IPO/LowerTypeTests.cpp
+++ llvm/lib/Transforms/IPO/LowerTypeTests.cpp
@@ -1512,14 +1512,18 @@
               FunctionType::get(Type::getVoidTy(M.getContext()), false),
               GlobalVariable::ExternalLinkage, FunctionName, &M);
 
-        if (Linkage == CFL_Definition)
-          F->eraseMetadata(LLVMContext::MD_type);
+        if (F->hasAvailableExternallyLinkage()) {
+          F->setLinkage(GlobalValue::ExternalLinkage);
+          F->deleteBody();
+          F->setComdat(nullptr);
+          F->clearMetadata();
+        }
 
         if (F->isDeclaration()) {
           if (Linkage == CFL_WeakDeclaration)
             F->setLinkage(GlobalValue::ExternalWeakLinkage);
 
-          SmallVector<MDNode *, 2> Types;
+          F->eraseMetadata(LLVMContext::MD_type);
           for (unsigned I = 2; I < FuncMD->getNumOperands(); ++I)
             F->addMetadata(LLVMContext::MD_type,
                            *cast<MDNode>(FuncMD->getOperand(I).get()));


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