[llvm] [BitcodeReader] Avoid quadratic complexity in intrinsic upgrade (PR #150032)

[Nikita Popov via llvm-commits]

https://github.com/nikic created https://github.com/llvm/llvm-project/pull/150032

When materializing a function, we'd upgrade all calls to all upgraded intrinsics. However, this would operate on all calls to the intrinsic (including previously materialized ones), which leads to quadratic complexity.

Instead, only upgrade the calls that are in the materialized function.

This fixes a compile-time regression introduced by #149310.

>From d2601dbc1427f3eb3b60bec2c0f6448cc1ca93fa Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Tue, 22 Jul 2025 15:20:03 +0200
Subject: [PATCH] [BitcodeReader] Avoid quadratic complexity in intrinsic
 upgrade

When materializing a function, we'd upgrade all calls to all
upgraded intrinsics. However, this would operate on all calls to
the intrinsic (including previously materialized ones), which
leads to quadratic complexity.

Instead, only upgrade the calls that are in the materialized
function.

This fixes a compile-time regression introduced by #149310.
---
 llvm/lib/Bitcode/Reader/BitcodeReader.cpp | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index f76368357a9c3..290d873c632c9 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -7015,13 +7015,6 @@ Error BitcodeReader::materialize(GlobalValue *GV) {
   if (StripDebugInfo)
     stripDebugInfo(*F);
 
-  // Upgrade any old intrinsic calls in the function.
-  for (auto &I : UpgradedIntrinsics) {
-    for (User *U : llvm::make_early_inc_range(I.first->materialized_users()))
-      if (CallInst *CI = dyn_cast<CallInst>(U))
-        UpgradeIntrinsicCall(CI, I.second);
-  }
-
   // Finish fn->subprogram upgrade for materialized functions.
   if (DISubprogram *SP = MDLoader->lookupSubprogramForFunction(F))
     F->setSubprogram(SP);
@@ -7037,7 +7030,7 @@ Error BitcodeReader::materialize(GlobalValue *GV) {
     }
   }
 
-  for (auto &I : instructions(F)) {
+  for (auto &I : make_early_inc_range(instructions(F))) {
     // "Upgrade" older incorrect branch weights by dropping them.
     if (auto *MD = I.getMetadata(LLVMContext::MD_prof)) {
       if (MD->getOperand(0) != nullptr && isa<MDString>(MD->getOperand(0))) {
@@ -7068,8 +7061,8 @@ Error BitcodeReader::materialize(GlobalValue *GV) {
       }
     }
 
-    // Remove incompatible attributes on function calls.
     if (auto *CI = dyn_cast<CallBase>(&I)) {
+      // Remove incompatible attributes on function calls.
       CI->removeRetAttrs(AttributeFuncs::typeIncompatible(
           CI->getFunctionType()->getReturnType(), CI->getRetAttributes()));
 
@@ -7077,6 +7070,13 @@ Error BitcodeReader::materialize(GlobalValue *GV) {
         CI->removeParamAttrs(ArgNo, AttributeFuncs::typeIncompatible(
                                         CI->getArgOperand(ArgNo)->getType(),
                                         CI->getParamAttributes(ArgNo)));
+
+      // Upgrade intrinsics.
+      if (Function *OldFn = CI->getCalledFunction()) {
+        auto It = UpgradedIntrinsics.find(OldFn);
+        if (It != UpgradedIntrinsics.end())
+          UpgradeIntrinsicCall(CI, It->second);
+      }
     }
   }