[DirectX] Remove trivially dead functions at linkage finalize

llvm/lib/Target/DirectX/DXILFinalizeLinkage.cpp

@@ -19,20 +19,20 @@
 using namespace llvm;
 
 static bool finalizeLinkage(Module &M) {
-  SmallPtrSet<Function *, 8> EntriesAndExports;
+  SmallPtrSet<Function *, 8> Funcs;
 
   // Find all entry points and export functions
   for (Function &EF : M.functions()) {
-    if (!EF.hasFnAttribute("hlsl.shader") && !EF.hasFnAttribute("hlsl.export"))
+    if (EF.hasFnAttribute("hlsl.shader") || EF.hasFnAttribute("hlsl.export"))
       continue;
-    EntriesAndExports.insert(&EF);
+    Funcs.insert(&EF);
   }
 
-  for (Function &F : M.functions()) {
-    if (F.getLinkage() == GlobalValue::ExternalLinkage &&
-        !EntriesAndExports.contains(&F)) {
-      F.setLinkage(GlobalValue::InternalLinkage);
-    }
+  for (Function *F : Funcs) {
+    if (F->getLinkage() == GlobalValue::ExternalLinkage)
+      F->setLinkage(GlobalValue::InternalLinkage);
+    if (F->hasFnAttribute(Attribute::AlwaysInline) && F->isDefTriviallyDead())
+      M.getFunctionList().erase(F);
   }
 
   return false;

llvm/test/CodeGen/DirectX/finalize-linkage-remove-dead.ll

@@ -0,0 +1,80 @@
+; RUN: opt -S -dxil-finalize-linkage -mtriple=dxil-unknown-shadermodel6.5-compute %s | FileCheck %s
+; RUN: llc %s --filetype=asm -o - | FileCheck %s
+
+target triple = "dxilv1.5-pc-shadermodel6.5-compute"
+
+; Confirm that DXILFinalizeLinkage will remove functions that have compatible
+; linkage and are not called from anywhere. This should be any function that
+; is not explicitly marked noinline or export and is not an entry point.
+
+; Not called nor marked with any linking or inlining attributes.
+; CHECK-NOT: define {{.*}}doNothingNothing
+define void @"?doNothingNothing@@YAXXZ"() #0 {
+entry:
+  ret void
+}
+
+; Marked internal, this should be removed.
+; CHECK-NOT: define {{.*}}doNothingInternally
+define internal void @"?doNothingInternally@@YAXXZ"() #0 {
+entry:
+  ret void
+}
+
+; Marked external, which should become internal and be removed.
+; CHECK-NOT: define {{.*}}doNothingExternally
+define external void @"?doNothingExternally@@YAXXZ"() #0 {
+entry:
+  ret void
+}
+
+; Not called nor marked with any linking or inlining attributes.
+; CHECK: define internal void @"?doSomethingSomething@@YAXXZ"() #0
+define void @"?doSomethingSomething@@YAXXZ"() #0 {
+entry:
+  ret void
+}
+
+; Marked internal, this should be removed.
+; CHECK: define internal void @"?doSomethingInternally@@YAXXZ"() #0
+define internal void @"?doSomethingInternally@@YAXXZ"() #0 {
+entry:
+  ret void
+}
+
+; Marked external, which should become internal and be removed.
+; CHECK: define internal void @"?doSomethingExternally@@YAXXZ"() #0
+define external void @"?doSomethingExternally@@YAXXZ"() #0 {
+entry:
+  ret void
+}
+
+; Lacks alwaysinline attribute. Should remain.
+; CHECK: define internal void @"?doNothingDefault@@YAXXZ"() #1
+define void @"?doNothingDefault@@YAXXZ"() #1 {
+entry:
+  ret void
+}
+
+; Has noinline attribute. Should remain.
+; CHECK: define {{.*}}doNothingNoinline
+define void @"?doNothingNoinline@@YAXXZ"() #2 {
+entry:
+  ret void
+}
+
+; Entry point function should stay.
+; CHECK: define void @main() #3
+define void @main() #3 {
+entry:
+  call void @"?doSomethingSomething@@YAXXZ"() #4
+  call void @"?doSomethingInternally@@YAXXZ"() #4
+  call void @"?doSomethingExternally@@YAXXZ"() #4
+  ret void
+}
+
+attributes #0 = { alwaysinline convergent norecurse nounwind }
+attributes #1 = { convergent norecurse nounwind }
+attributes #2 = { convergent noinline norecurse nounwind }
+attributes #3 = { convergent noinline norecurse "hlsl.numthreads"="1,1,1" "hlsl.shader"="compute" }
+attributes #4 = { convergent }