[Metadata] Handle memprof, callsite merging when one is missing.

For memprof and callsite metadata we want to pick one deterministically
and keep that even if one of them may be missing.

Author: Snehasish Kumar

llvm/lib/Transforms/Utils/Local.cpp

@@ -3355,8 +3355,14 @@ static void combineMetadata(Instruction *K, const Instruction *J,
       case LLVMContext::MD_invariant_group:
         // Preserve !invariant.group in K.
         break;
+      // Keep empty cases for mmra, memprof, and callsite to prevent them from
+      // being removed as unknown metadata. The actual merging is handled
+      // separately below.
       case LLVMContext::MD_mmra:
-        // Combine MMRAs
+        [[fallthrough]];
+      case LLVMContext::MD_memprof:
+        [[fallthrough]];
+      case LLVMContext::MD_callsite:
         break;
       case LLVMContext::MD_align:
         if (!AAOnly && (DoesKMove || !K->hasMetadata(LLVMContext::MD_noundef)))
@@ -3369,14 +3375,6 @@ static void combineMetadata(Instruction *K, const Instruction *J,
           K->setMetadata(Kind,
             MDNode::getMostGenericAlignmentOrDereferenceable(JMD, KMD));
         break;
-      case LLVMContext::MD_memprof:
-        if (!AAOnly)
-          K->setMetadata(Kind, MDNode::getMergedMemProfMetadata(KMD, JMD));
-        break;
-      case LLVMContext::MD_callsite:
-        if (!AAOnly)
-          K->setMetadata(Kind, MDNode::getMergedCallsiteMetadata(KMD, JMD));
-        break;
       case LLVMContext::MD_preserve_access_index:
         // Preserve !preserve.access.index in K.
         break;
@@ -3420,6 +3418,26 @@ static void combineMetadata(Instruction *K, const Instruction *J,
     K->setMetadata(LLVMContext::MD_mmra,
                    MMRAMetadata::combine(K->getContext(), JMMRA, KMMRA));
   }
+
+  // Merge memprof metadata.
+  // Handle separately to support cases where only one instruction has the
+  // metadata.
+  auto JMemProf = J->getMetadata(LLVMContext::MD_memprof);
+  auto KMemProf = K->getMetadata(LLVMContext::MD_memprof);
+  if (!AAOnly && (JMemProf || KMemProf)) {
+    K->setMetadata(LLVMContext::MD_memprof,
+                   MDNode::getMergedMemProfMetadata(KMemProf, JMemProf));
+  }
+
+  // Merge callsite metadata.
+  // Handle separately to support cases where only one instruction has the
+  // metadata.
+  auto JCallSite = J->getMetadata(LLVMContext::MD_callsite);
+  auto KCallSite = K->getMetadata(LLVMContext::MD_callsite);
+  if (!AAOnly && (JCallSite || KCallSite)) {
+    K->setMetadata(LLVMContext::MD_callsite,
+                   MDNode::getMergedCallsiteMetadata(KCallSite, JCallSite));
+  }
 }
 
 void llvm::combineMetadataForCSE(Instruction *K, const Instruction *J,

llvm/test/Transforms/SimplifyCFG/merge-calls-memprof.ll

@@ -1,5 +1,3 @@
-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
-
 ;; Test to ensure that memprof related metadata is not dropped when
 ;; instructions are combined. Currently the metadata from the first instruction
 ;; is kept, which prevents full loss of profile context information.
@@ -32,6 +30,51 @@ if.end:                                           ; preds = %if.else, %if.then
   ret ptr %x.0
 }
 
+define dso_local noundef nonnull ptr @_Z9test_leftb(i1 noundef zeroext %b) local_unnamed_addr #0 {
+; CHECK-LABEL: define dso_local noundef nonnull ptr @_Z9test_leftb(
+; CHECK-SAME: i1 noundef zeroext [[B:%.*]]) local_unnamed_addr {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[CALL:%.*]] = call noalias noundef nonnull dereferenceable(4) ptr @_Znwm(i64 noundef 4), !memprof [[META0:![0-9]+]], !callsite [[META3:![0-9]+]]
+; CHECK-NEXT:    ret ptr [[CALL]]
+;
+entry:
+  br i1 %b, label %if.then, label %if.else
+
+if.then:                                          ; preds = %entry
+  %call = call noalias noundef nonnull dereferenceable(4) ptr @_Znwm(i64 noundef 4), !memprof !0, !callsite !3
+  br label %if.end
+
+if.else:                                          ; preds = %entry
+  %call1 = call noalias noundef nonnull dereferenceable(4) ptr @_Znwm(i64 noundef 4)
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  %x.0 = phi ptr [ %call, %if.then ], [ %call1, %if.else ]
+  ret ptr %x.0
+}
+
+define dso_local noundef nonnull ptr @_Z10test_rightb(i1 noundef zeroext %b) local_unnamed_addr #0 {
+; CHECK-LABEL: define dso_local noundef nonnull ptr @_Z10test_rightb(
+; CHECK-SAME: i1 noundef zeroext [[B:%.*]]) local_unnamed_addr {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[CALL:%.*]] = call noalias noundef nonnull dereferenceable(4) ptr @_Znwm(i64 noundef 4), !memprof [[META4:![0-9]+]], !callsite [[META7:![0-9]+]]
+; CHECK-NEXT:    ret ptr [[CALL]]
+;
+entry:
+  br i1 %b, label %if.then, label %if.else
+
+if.then:                                          ; preds = %entry
+  %call = call noalias noundef nonnull dereferenceable(4) ptr @_Znwm(i64 noundef 4)
+  br label %if.end
+
+if.else:                                          ; preds = %entry
+  %call1 = call noalias noundef nonnull dereferenceable(4) ptr @_Znwm(i64 noundef 4), !memprof !4, !callsite !7
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  %x.0 = phi ptr [ %call, %if.then ], [ %call1, %if.else ]
+  ret ptr %x.0
+}
 
 declare ptr @_Znwm(i64) nounwind readonly
 
@@ -43,9 +86,13 @@ declare ptr @_Znwm(i64) nounwind readonly
 !5 = !{!6, !"cold"}
 !6 = !{i64 123, i64 -2101080423462424381, i64 5188446645037944434}
 !7 = !{i64 123}
-;.
+
 ; CHECK: [[META0]] = !{[[META1:![0-9]+]]}
 ; CHECK: [[META1]] = !{[[META2:![0-9]+]], !"notcold"}
 ; CHECK: [[META2]] = !{i64 -852997907418798798, i64 -2101080423462424381, i64 5188446645037944434}
 ; CHECK: [[META3]] = !{i64 -852997907418798798}
-;.
+; CHECK: [[META4]] = !{[[META5:![0-9]+]]}
+; CHECK: [[META5]] = !{[[META6:![0-9]+]], !"cold"}
+; CHECK: [[META6]] = !{i64 123, i64 -2101080423462424381, i64 5188446645037944434}
+; CHECK: [[META7]] = !{i64 123}
+