[llvm] Always check the function attribute to determine checksum mismatch for available_externally functions (PR #87279)

[Lei Wang via llvm-commits]

https://github.com/wlei-llvm created https://github.com/llvm/llvm-project/pull/87279

`pseudo_probe_desc` could still be available for import functions, this happens when an internal function(the desc is computed based on) is substituted by the `available_externally` function, e.g. the template function, their mismatch state could be different and we should use state from the new one. Hence, changed it to always check the function attribute to determine checksum mismatch for `available_externally` functions.

>From 6e87aaf66863cb17bfc158fec45924698f7834da Mon Sep 17 00:00:00 2001
From: wlei <wlei at fb.com>
Date: Mon, 1 Apr 2024 12:41:06 -0700
Subject: [PATCH] Always check thhe unction attribute to determine checksum
 mismatch for available_externally functions

---
 .../Utils/SampleProfileLoaderBaseImpl.h       | 23 +++++++++++++------
 .../pseudo-probe-callee-profile-mismatch.ll   |  9 +++++---
 2 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/llvm/include/llvm/Transforms/Utils/SampleProfileLoaderBaseImpl.h b/llvm/include/llvm/Transforms/Utils/SampleProfileLoaderBaseImpl.h
index d898ee58307ead..3098bba115c328 100644
--- a/llvm/include/llvm/Transforms/Utils/SampleProfileLoaderBaseImpl.h
+++ b/llvm/include/llvm/Transforms/Utils/SampleProfileLoaderBaseImpl.h
@@ -129,16 +129,25 @@ class PseudoProbeManager {
 
   bool profileIsValid(const Function &F, const FunctionSamples &Samples) const {
     const auto *Desc = getDesc(F);
-    assert((LTOPhase != ThinOrFullLTOPhase::ThinLTOPostLink || !Desc ||
+    bool IsAvailableExternallyLinkage =
+        GlobalValue::isAvailableExternallyLinkage(F.getLinkage());
+    // Always check the function attribute to determine checksum mismatch for
+    // `available_externally` functions even their desc is available. This is
+    // because the desc is computed based on the original internal function
+    // which is substituted by the `available_externally` function, their
+    // mismatch state could be different and we should use state from the new
+    // one.
+    assert((LTOPhase != ThinOrFullLTOPhase::ThinLTOPostLink ||
+            IsAvailableExternallyLinkage || !Desc ||
             profileIsHashMismatched(*Desc, Samples) ==
                 F.hasFnAttribute("profile-checksum-mismatch")) &&
-           "In post-link, profile checksum matching state doesn't match "
-           "function 'profile-checksum-mismatch' attribute.");
+           "In post-link, profile checksum matching state doesn't match the "
+           "internal function's 'profile-checksum-mismatch' attribute.");
     (void)LTOPhase;
-    // The desc for import function is unavailable. Check the function attribute
-    // for mismatch.
-    return (!Desc && !F.hasFnAttribute("profile-checksum-mismatch")) ||
-           (Desc && !profileIsHashMismatched(*Desc, Samples));
+    if (IsAvailableExternallyLinkage || !Desc)
+      return !F.hasFnAttribute("profile-checksum-mismatch");
+
+    return Desc && !profileIsHashMismatched(*Desc, Samples);
   }
 };
 
diff --git a/llvm/test/Transforms/SampleProfile/pseudo-probe-callee-profile-mismatch.ll b/llvm/test/Transforms/SampleProfile/pseudo-probe-callee-profile-mismatch.ll
index 4881937df101ac..43be142e7cf98f 100644
--- a/llvm/test/Transforms/SampleProfile/pseudo-probe-callee-profile-mismatch.ll
+++ b/llvm/test/Transforms/SampleProfile/pseudo-probe-callee-profile-mismatch.ll
@@ -1,7 +1,9 @@
 ; REQUIRES: x86_64-linux
 ; REQUIRES: asserts
-; RUN: opt < %s -passes=sample-profile -sample-profile-file=%S/Inputs/pseudo-probe-callee-profile-mismatch.prof --salvage-stale-profile -S --debug-only=sample-profile,sample-profile-matcher,sample-profile-impl  -pass-remarks=inline 2>&1 | FileCheck %s
+; RUN: opt < %s -passes='thinlto<O2>' -pgo-kind=pgo-sample-use-pipeline  -sample-profile-file=%S/Inputs/pseudo-probe-callee-profile-mismatch.prof --salvage-stale-profile -S --debug-only=sample-profile,sample-profile-matcher,sample-profile-impl  -pass-remarks=inline 2>&1 | FileCheck %s
 
+; There is no profile-checksum-mismatch attr, even the checksum is mismatched in the pseudo_probe_desc, it doesn't run the matching.
+; CHECK-NOT: Run stale profile matching for main
 
 ; CHECK: Run stale profile matching for bar
 ; CHECK: Callsite with callee:baz is matched from 4 to 2
@@ -14,7 +16,7 @@
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
-define i32 @main() #0 {
+define available_externally i32 @main() #0 {
   %1 = call i32 @bar(), !dbg !13
   ret i32 0
 }
@@ -47,7 +49,8 @@ attributes #1 = { "profile-checksum-mismatch" "use-sample-profile" }
 !9 = distinct !DICompileUnit(language: DW_LANG_C11, file: !10, producer: "clang version 19.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
 !10 = !DIFile(filename: "test2.c", directory: "/home/test", checksumkind: CSK_MD5, checksum: "553093afc026f9c73562eb3b0c5b7532")
 !11 = !{i32 2, !"Debug Info Version", i32 3}
-!12 = !{i64 -2624081020897602054, i64 281582081721716, !"main"}
+; Make a checksum mismatch in the pseudo_probe_desc
+!12 = !{i64 -2624081020897602054, i64 123456, !"main"}
 !13 = !DILocation(line: 8, column: 10, scope: !14)
 !14 = !DILexicalBlockFile(scope: !15, file: !1, discriminator: 186646591)
 !15 = distinct !DILexicalBlock(scope: !16, file: !1, line: 7, column: 40)