Propagate implicit.ref metadata when inlining.

Propagate the metadata from callee to caller on inlining. Also adds a
test verifying that the metadata is maintained when cloning a function.

Author: mandlebug

llvm/lib/Transforms/Utils/InlineFunction.cpp

@@ -2830,6 +2830,15 @@ void llvm::InlineFunctionImpl(CallBase &CB, InlineFunctionInfo &IFI,
     // Propagate metadata on the callsite if necessary.
     PropagateCallSiteMetadata(CB, FirstNewBlock, Caller->end());
 
+    // Propagate implicit ref metadata.
+    if (CalledFunc->hasMetadata(LLVMContext::MD_implicit_ref)) {
+      SmallVector<MDNode *> MDs;
+      CalledFunc->getMetadata(LLVMContext::MD_implicit_ref, MDs);
+      for (MDNode *MD : MDs) {
+        Caller->addMetadata(LLVMContext::MD_implicit_ref, *MD);
+      }
+    }
+
     // Register any cloned assumptions.
     if (IFI.GetAssumptionCache)
       for (BasicBlock &NewBlock :

llvm/test/Transforms/FunctionSpecialization/function-specialization-implicit-ref.ll

@@ -0,0 +1,43 @@
+; RUN: opt -passes="ipsccp<func-spec>" -S -force-specialization < %s 2>&1 | FileCheck %s
+
+@a = global i32 1
+
+define i64 @main(i64 %x, i1 %flag) {
+entry:
+  br i1 %flag, label %plus, label %minus
+
+plus:
+  %tmp0 = call i64 @compute(i64 %x, ptr @plus)
+  br label %merge
+
+minus:
+  %tmp1 = call i64 @compute(i64 %x, ptr @minus)
+  br label %merge
+
+merge:
+  %tmp2 = phi i64 [ %tmp0, %plus ], [ %tmp1, %minus]
+  ret i64 %tmp2
+}
+
+define internal i64 @compute(i64 %x, ptr %binop) !implicit.ref !0 {
+entry:
+  %tmp0 = call i64 %binop(i64 %x)
+  ret i64 %tmp0
+}
+
+define internal i64 @plus(i64 %x) {
+entry:
+  %tmp0 = add i64 %x, 1
+  ret i64 %tmp0
+}
+
+define internal i64 @minus(i64 %x) {
+entry:
+  %tmp0 = sub i64 %x, 1
+  ret i64 %tmp0
+}
+
+!0 = !{ptr @a}
+
+; CHECK: @compute.specialized.1(i64 %x, ptr %binop) !implicit.ref !0
+; CHECK: @compute.specialized.2(i64 %x, ptr %binop) !implicit.ref !0

llvm/test/Transforms/Inline/inline-ref-metadata.ll

@@ -0,0 +1,50 @@
+; RUN: opt < %s -passes='cgscc(inline)' -S | FileCheck %s
+
+@a = global i32 1
+@b = global i32 2
+@c = global double 3.141593e+00
+
+define i32 @callee1() !implicit.ref !0 {
+  ret i32 0
+}
+
+define i32 @callee2() !implicit.ref !1 {
+  ret i32 1
+}
+
+define i32 @callee3() {
+  %i = call i32 @callee2()
+  ret i32 %i
+}
+; CHECK: @callee3() !implicit.ref !1
+
+define i32 @caller1() {
+  %i = call i32 @callee1()
+  ret i32 %i
+}
+; CHECK: @caller1() !implicit.ref !0
+
+define i32 @caller2() !implicit.ref !2 {
+  %i = call i32 @callee1()
+  ret i32 %i
+}
+; CHECK: @caller2() !implicit.ref !2 !implicit.ref !0
+
+define i32 @caller3() {
+  %i = call i32 @caller4()
+  ret i32 %i
+}
+; CHECK: @caller3() !implicit.ref !0 !implicit.ref !1
+
+define i32 @caller4() {
+  %a = call i32 @callee1()
+  %b = call i32 @callee2()
+  %add = add i32 %a, %b
+  ret i32 %add
+}
+; CHECK: @caller4() !implicit.ref !0 !implicit.ref !1
+
+!0 = !{ptr @a}
+!1 = !{ptr @b}
+!2 = !{ptr @c}
+