[InstCombine][MemProf] Preserve all metadata

[melver]

When rewriting operator new calls to their hot/cold variants for PGHO,
!alloc_token metadata was being dropped. This metadata is required by
the AllocToken pass to correctly instrument the optimized allocation.

Fix it by preserving all metadata.

---

This change is part of the following series:

1. [InstCombine][MemProf] Preserve all metadata #169242
2. [Clang][MemProf] Add end-to-end test for PGHO rewriting #169243
3. [LTO][AllocToken] Support AllocToken instrumentation in backend #169358
4. [Clang] Make -falloc-token-mode a hidden frontend option #169359
5. [Clang][CodeGen] Remove explicit insertion of AllocToken pass #169360

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

Author: Marco Elver (melver)

Changes

When rewriting operator new calls to their hot/cold variants for PGHO,
!alloc_token metadata was being dropped. This metadata is required by
the AllocToken pass to correctly instrument the optimized allocation.
This change ensures the metadata is copied to the new instruction.

Fix it by preserving the metadata.

---

Full diff: https://github.com/llvm/llvm-project/pull/169242.diff

2 Files Affected:

• (modified) llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp (+43-37)
• (modified) llvm/test/Transforms/InstCombine/simplify-libcalls-new.ll (+13)

diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 4f4e64b1c7b70..4ba4e484fb77d 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -1806,119 +1806,125 @@ Value *LibCallSimplifier::optimizeNew(CallInst *CI, IRBuilderBase &B,
   // better to replace the hinted call with a non hinted call, to avoid the
   // extra parameter and the if condition check of the hint value in the
   // allocator. This can be considered in the future.
+  Value *NewCall = nullptr;
   switch (Func) {
   case LibFunc_Znwm12__hot_cold_t:
     if (OptimizeExistingHotColdNew)
-      return emitHotColdNew(CI->getArgOperand(0), B, TLI,
-                            LibFunc_Znwm12__hot_cold_t, HotCold);
+      NewCall = emitHotColdNew(CI->getArgOperand(0), B, TLI,
+                               LibFunc_Znwm12__hot_cold_t, HotCold);
     break;
   case LibFunc_Znwm:
-    return emitHotColdNew(CI->getArgOperand(0), B, TLI,
-                          LibFunc_Znwm12__hot_cold_t, HotCold);
+    NewCall = emitHotColdNew(CI->getArgOperand(0), B, TLI,
+                             LibFunc_Znwm12__hot_cold_t, HotCold);
     break;
   case LibFunc_Znam12__hot_cold_t:
     if (OptimizeExistingHotColdNew)
-      return emitHotColdNew(CI->getArgOperand(0), B, TLI,
-                            LibFunc_Znam12__hot_cold_t, HotCold);
+      NewCall = emitHotColdNew(CI->getArgOperand(0), B, TLI,
+                               LibFunc_Znam12__hot_cold_t, HotCold);
     break;
   case LibFunc_Znam:
-    return emitHotColdNew(CI->getArgOperand(0), B, TLI,
-                          LibFunc_Znam12__hot_cold_t, HotCold);
+    NewCall = emitHotColdNew(CI->getArgOperand(0), B, TLI,
+                             LibFunc_Znam12__hot_cold_t, HotCold);
     break;
   case LibFunc_ZnwmRKSt9nothrow_t12__hot_cold_t:
     if (OptimizeExistingHotColdNew)
-      return emitHotColdNewNoThrow(
+      NewCall = emitHotColdNewNoThrow(
           CI->getArgOperand(0), CI->getArgOperand(1), B, TLI,
           LibFunc_ZnwmRKSt9nothrow_t12__hot_cold_t, HotCold);
     break;
   case LibFunc_ZnwmRKSt9nothrow_t:
-    return emitHotColdNewNoThrow(CI->getArgOperand(0), CI->getArgOperand(1), B,
-                                 TLI, LibFunc_ZnwmRKSt9nothrow_t12__hot_cold_t,
-                                 HotCold);
+    NewCall = emitHotColdNewNoThrow(
+        CI->getArgOperand(0), CI->getArgOperand(1), B, TLI,
+        LibFunc_ZnwmRKSt9nothrow_t12__hot_cold_t, HotCold);
     break;
   case LibFunc_ZnamRKSt9nothrow_t12__hot_cold_t:
     if (OptimizeExistingHotColdNew)
-      return emitHotColdNewNoThrow(
+      NewCall = emitHotColdNewNoThrow(
           CI->getArgOperand(0), CI->getArgOperand(1), B, TLI,
           LibFunc_ZnamRKSt9nothrow_t12__hot_cold_t, HotCold);
     break;
   case LibFunc_ZnamRKSt9nothrow_t:
-    return emitHotColdNewNoThrow(CI->getArgOperand(0), CI->getArgOperand(1), B,
-                                 TLI, LibFunc_ZnamRKSt9nothrow_t12__hot_cold_t,
-                                 HotCold);
+    NewCall = emitHotColdNewNoThrow(
+        CI->getArgOperand(0), CI->getArgOperand(1), B, TLI,
+        LibFunc_ZnamRKSt9nothrow_t12__hot_cold_t, HotCold);
     break;
   case LibFunc_ZnwmSt11align_val_t12__hot_cold_t:
     if (OptimizeExistingHotColdNew)
-      return emitHotColdNewAligned(
+      NewCall = emitHotColdNewAligned(
           CI->getArgOperand(0), CI->getArgOperand(1), B, TLI,
           LibFunc_ZnwmSt11align_val_t12__hot_cold_t, HotCold);
     break;
   case LibFunc_ZnwmSt11align_val_t:
-    return emitHotColdNewAligned(CI->getArgOperand(0), CI->getArgOperand(1), B,
-                                 TLI, LibFunc_ZnwmSt11align_val_t12__hot_cold_t,
-                                 HotCold);
+    NewCall = emitHotColdNewAligned(
+        CI->getArgOperand(0), CI->getArgOperand(1), B, TLI,
+        LibFunc_ZnwmSt11align_val_t12__hot_cold_t, HotCold);
     break;
   case LibFunc_ZnamSt11align_val_t12__hot_cold_t:
     if (OptimizeExistingHotColdNew)
-      return emitHotColdNewAligned(
+      NewCall = emitHotColdNewAligned(
           CI->getArgOperand(0), CI->getArgOperand(1), B, TLI,
           LibFunc_ZnamSt11align_val_t12__hot_cold_t, HotCold);
     break;
   case LibFunc_ZnamSt11align_val_t:
-    return emitHotColdNewAligned(CI->getArgOperand(0), CI->getArgOperand(1), B,
-                                 TLI, LibFunc_ZnamSt11align_val_t12__hot_cold_t,
-                                 HotCold);
+    NewCall = emitHotColdNewAligned(
+        CI->getArgOperand(0), CI->getArgOperand(1), B, TLI,
+        LibFunc_ZnamSt11align_val_t12__hot_cold_t, HotCold);
     break;
   case LibFunc_ZnwmSt11align_val_tRKSt9nothrow_t12__hot_cold_t:
     if (OptimizeExistingHotColdNew)
-      return emitHotColdNewAlignedNoThrow(
+      NewCall = emitHotColdNewAlignedNoThrow(
           CI->getArgOperand(0), CI->getArgOperand(1), CI->getArgOperand(2), B,
           TLI, LibFunc_ZnwmSt11align_val_tRKSt9nothrow_t12__hot_cold_t,
           HotCold);
     break;
   case LibFunc_ZnwmSt11align_val_tRKSt9nothrow_t:
-    return emitHotColdNewAlignedNoThrow(
+    NewCall = emitHotColdNewAlignedNoThrow(
         CI->getArgOperand(0), CI->getArgOperand(1), CI->getArgOperand(2), B,
         TLI, LibFunc_ZnwmSt11align_val_tRKSt9nothrow_t12__hot_cold_t, HotCold);
     break;
   case LibFunc_ZnamSt11align_val_tRKSt9nothrow_t12__hot_cold_t:
     if (OptimizeExistingHotColdNew)
-      return emitHotColdNewAlignedNoThrow(
+      NewCall = emitHotColdNewAlignedNoThrow(
           CI->getArgOperand(0), CI->getArgOperand(1), CI->getArgOperand(2), B,
           TLI, LibFunc_ZnamSt11align_val_tRKSt9nothrow_t12__hot_cold_t,
           HotCold);
     break;
   case LibFunc_ZnamSt11align_val_tRKSt9nothrow_t:
-    return emitHotColdNewAlignedNoThrow(
+    NewCall = emitHotColdNewAlignedNoThrow(
         CI->getArgOperand(0), CI->getArgOperand(1), CI->getArgOperand(2), B,
         TLI, LibFunc_ZnamSt11align_val_tRKSt9nothrow_t12__hot_cold_t, HotCold);
     break;
   case LibFunc_size_returning_new:
-    return emitHotColdSizeReturningNew(CI->getArgOperand(0), B, TLI,
-                                       LibFunc_size_returning_new_hot_cold,
-                                       HotCold);
+    NewCall = emitHotColdSizeReturningNew(CI->getArgOperand(0), B, TLI,
+                                          LibFunc_size_returning_new_hot_cold,
+                                          HotCold);
     break;
   case LibFunc_size_returning_new_hot_cold:
     if (OptimizeExistingHotColdNew)
-      return emitHotColdSizeReturningNew(CI->getArgOperand(0), B, TLI,
-                                         LibFunc_size_returning_new_hot_cold,
-                                         HotCold);
+      NewCall = emitHotColdSizeReturningNew(CI->getArgOperand(0), B, TLI,
+                                            LibFunc_size_returning_new_hot_cold,
+                                            HotCold);
     break;
   case LibFunc_size_returning_new_aligned:
-    return emitHotColdSizeReturningNewAligned(
+    NewCall = emitHotColdSizeReturningNewAligned(
         CI->getArgOperand(0), CI->getArgOperand(1), B, TLI,
         LibFunc_size_returning_new_aligned_hot_cold, HotCold);
     break;
   case LibFunc_size_returning_new_aligned_hot_cold:
     if (OptimizeExistingHotColdNew)
-      return emitHotColdSizeReturningNewAligned(
+      NewCall = emitHotColdSizeReturningNewAligned(
           CI->getArgOperand(0), CI->getArgOperand(1), B, TLI,
           LibFunc_size_returning_new_aligned_hot_cold, HotCold);
     break;
   default:
     return nullptr;
   }
-  return nullptr;
+
+  if (auto *NewCI = dyn_cast_or_null<Instruction>(NewCall))
+    if (MDNode *MD = CI->getMetadata(LLVMContext::MD_alloc_token))
+      NewCI->setMetadata(LLVMContext::MD_alloc_token, MD);
+
+  return NewCall;
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/llvm/test/Transforms/InstCombine/simplify-libcalls-new.ll b/llvm/test/Transforms/InstCombine/simplify-libcalls-new.ll
index 5a4fb04f5f2c0..2765c75f4d5e0 100644
--- a/llvm/test/Transforms/InstCombine/simplify-libcalls-new.ll
+++ b/llvm/test/Transforms/InstCombine/simplify-libcalls-new.ll
@@ -610,6 +610,16 @@ define void @size_returning_aligned_update_test() {
   ret void
 }
 
+;; Check that !alloc_token is preserved.
+; HOTCOLD-LABEL: @new_alloc_token()
+define void @new_alloc_token() {
+  ;; Attribute cold converted to __hot_cold_t cold value.
+  ; HOTCOLD: @_Znwm12__hot_cold_t(i64 10, i8 [[COLD]]), !alloc_token ![[ALLOC_TOKEN:[0-9]+]]
+  %call = call ptr @_Znwm(i64 10) #0, !alloc_token !0
+  call void @dummy(ptr %call)
+  ret void
+}
+
 ;; So that instcombine doesn't optimize out the call.
 declare void @dummy(ptr)
 
@@ -649,3 +659,6 @@ attributes #5 = { "memprof" = "hot" }
 attributes #8 = { "memprof" = "ambiguous" }
 
 attributes #6 = { nobuiltin allocsize(0) "memprof"="cold" }
+
+; CHECK: [[ALLOC_TOKEN]] = !{!"MyType", i1 false}
+!0 = !{!"MyType", i1 false}

[teresajohnson]

Hmm, looks like we are going to lose all MD, so this seems like a broader issue. Let me look and see if there are facilities for copying over all existing MD

[teresajohnson]

lgtm