[PATCH] D137982: [pgo] Avoid introducing relocations by using private alias

[Paul Kirth via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
paulkirth marked an inline comment as done.
Closed by commit rG2b8917f8ad79: [pgo] Avoid introducing relocations by using private alias (authored by paulkirth).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D137982/new/

https://reviews.llvm.org/D137982

Files:
  llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
  llvm/test/Transforms/PGOProfile/prof_avoid_relocs.ll


Index: llvm/test/Transforms/PGOProfile/prof_avoid_relocs.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/PGOProfile/prof_avoid_relocs.ll
@@ -0,0 +1,23 @@
+; RUN: opt -S -passes=pgo-instr-gen,instrprof < %s | FileCheck %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Test that we use private aliases to reference function addresses inside profile data
+
+; CHECK: @__profd_foo = private global {{.*}}, ptr @foo.1,
+; CHECK-NOT: @__profd_foo = private global {{.*}}, ptr @foo,
+; CHECK: @foo.1 = private alias i32 (i32), ptr @foo
+
+define i32 @foo(i32 %0) {
+; CHECK-LABEL: @foo(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[PGOCOUNT:%.*]] = load i64, ptr @__profc_foo, align 8
+; CHECK-NEXT:    [[TMP1:%.*]] = add i64 [[PGOCOUNT]], 1
+; CHECK-NEXT:    store i64 [[TMP1]], ptr @__profc_foo, align 8
+; CHECK-NEXT:    ret i32 0
+;
+entry:
+  ret i32 0
+}
+
Index: llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
===================================================================
--- llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
+++ llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
@@ -1014,9 +1014,17 @@
   };
   auto *DataTy = StructType::get(Ctx, makeArrayRef(DataTypes));
 
-  Constant *FunctionAddr = shouldRecordFunctionAddr(Fn)
-                               ? ConstantExpr::getBitCast(Fn, Int8PtrTy)
-                               : ConstantPointerNull::get(Int8PtrTy);
+  Constant *FunctionAddr;
+  if (shouldRecordFunctionAddr(Fn)) {
+    // When possible use a private alias to avoid relocations
+    Constant *Addr = !Fn->isDeclarationForLinker()
+                         ? static_cast<Constant *>(GlobalAlias::create(
+                               GlobalValue::PrivateLinkage, Fn->getName(), Fn))
+                         : Fn;
+    FunctionAddr = ConstantExpr::getBitCast(Addr, Int8PtrTy);
+  } else {
+    FunctionAddr = ConstantPointerNull::get(Int8PtrTy);
+  }
 
   Constant *Int16ArrayVals[IPVK_Last + 1];
   for (uint32_t Kind = IPVK_First; Kind <= IPVK_Last; ++Kind)


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