[FunctionComparator] Differentiate instructions passing different MDStrings

llvm/lib/Transforms/Utils/FunctionComparator.cpp

@@ -160,10 +160,23 @@ int FunctionComparator::cmpAttrs(const AttributeList L,
 int FunctionComparator::cmpMetadata(const Metadata *L,
                                     const Metadata *R) const {
   // TODO: the following routine coerce the metadata contents into constants
-  // before comparison.
+  // or MDStrings before comparison.
   // It ignores any other cases, so that the metadata nodes are considered
   // equal even though this is not correct.
   // We should structurally compare the metadata nodes to be perfect here.
+
+  auto *MDStringL = dyn_cast<MDString>(L);
+  auto *MDStringR = dyn_cast<MDString>(R);
+  if (MDStringL && MDStringR) {
+    if (MDStringL == MDStringR)
+      return 0;
+    return MDStringL->getString().compare(MDStringR->getString());
+  }
+  if (MDStringR)
+    return -1;
+  if (MDStringL)
+    return 1;
+
   auto *CL = dyn_cast<ConstantAsMetadata>(L);
   auto *CR = dyn_cast<ConstantAsMetadata>(R);
   if (CL == CR)
@@ -820,6 +833,21 @@ int FunctionComparator::cmpValues(const Value *L, const Value *R) const {
   if (ConstR)
     return -1;
 
+  const MetadataAsValue *MetadataValueL = dyn_cast<MetadataAsValue>(L);
+  const MetadataAsValue *MetadataValueR = dyn_cast<MetadataAsValue>(R);
+  if (MetadataValueL && MetadataValueR) {
+    if (MetadataValueL == MetadataValueR)
+      return 0;
+
+    return cmpMetadata(MetadataValueL->getMetadata(),
+                       MetadataValueR->getMetadata());
+  }
+
+  if (MetadataValueL)
+    return 1;
+  if (MetadataValueR)
+    return -1;
+
   const InlineAsm *InlineAsmL = dyn_cast<InlineAsm>(L);
   const InlineAsm *InlineAsmR = dyn_cast<InlineAsm>(R);
 

llvm/test/Transforms/MergeFunc/mergefunc-preserve-vfe-intrinsics.ll

@@ -0,0 +1,44 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
+; RUN: opt -passes=mergefunc -S %s | FileCheck %s
+
+; This test contains three identical functions, aside from the metadata
+; they pass to a function call. This test verifies that the function merger
+; pass is able to merge the two functions that are truly identical,
+; but the third that passes different metadata is preserved
+
+declare { ptr, i1 } @llvm.type.checked.load(ptr, i32, metadata)
+
+define i1 @merge_candidate_a(ptr %ptr, i32 %offset) {
+; CHECK-LABEL: define i1 @merge_candidate_a(
+; CHECK-SAME: ptr [[PTR:%.*]], i32 [[OFFSET:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = call { ptr, i1 } @llvm.type.checked.load(ptr [[PTR]], i32 [[OFFSET]], metadata !"common_metadata")
+; CHECK-NEXT:    [[TMP2:%.*]] = extractvalue { ptr, i1 } [[TMP1]], 1
+; CHECK-NEXT:    ret i1 [[TMP2]]
+;
+  %1 = call { ptr, i1 } @llvm.type.checked.load(ptr %ptr, i32 %offset, metadata !"common_metadata")
+  %2 = extractvalue { ptr, i1 } %1, 1
+  ret i1 %2
+}
+
+define i1 @merge_candidate_c(ptr %ptr, i32 %offset) {
+; CHECK-LABEL: define i1 @merge_candidate_c(
+; CHECK-SAME: ptr [[PTR:%.*]], i32 [[OFFSET:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = call { ptr, i1 } @llvm.type.checked.load(ptr [[PTR]], i32 [[OFFSET]], metadata !"different_metadata")
+; CHECK-NEXT:    [[TMP2:%.*]] = extractvalue { ptr, i1 } [[TMP1]], 1
+; CHECK-NEXT:    ret i1 [[TMP2]]
+;
+  %1 = call { ptr, i1 } @llvm.type.checked.load(ptr %ptr, i32 %offset, metadata !"different_metadata")
+  %2 = extractvalue { ptr, i1 } %1, 1
+  ret i1 %2
+}
+
+define i1 @merge_candidate_b(ptr %ptr, i32 %offset) {
+; CHECK-LABEL: define i1 @merge_candidate_b(
+; CHECK-SAME: ptr [[TMP0:%.*]], i32 [[TMP1:%.*]]) {
+; CHECK-NEXT:    [[TMP3:%.*]] = tail call i1 @merge_candidate_a(ptr [[TMP0]], i32 [[TMP1]])
+; CHECK-NEXT:    ret i1 [[TMP3]]
+;
+  %1 = call { ptr, i1 } @llvm.type.checked.load(ptr %ptr, i32 %offset, metadata !"common_metadata")
+  %2 = extractvalue { ptr, i1 } %1, 1
+  ret i1 %2
+}