[PATCH] D96083: [LTT] Don't attempt to lower type tests used only by assumes

[Teresa Johnson via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG3a27933ec285: [LTT] Don't attempt to lower type tests used only by assumes (authored by tejohnson).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D96083/new/

https://reviews.llvm.org/D96083

Files:
  llvm/lib/Transforms/IPO/LowerTypeTests.cpp
  llvm/test/Transforms/LowerTypeTests/pr48245.ll


Index: llvm/test/Transforms/LowerTypeTests/pr48245.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/LowerTypeTests/pr48245.ll
@@ -0,0 +1,48 @@
+; Test to ensure type tests that are only used in assumes are ignored by
+; LowerTypeTests (in the normal pass sequence they will be stripped out
+; by a subsequent special LTT invocation).
+
+; RUN: opt -S -passes=lowertypetests < %s | FileCheck %s
+
+; ModuleID = 'pr48245.o'
+source_filename = "pr48245.cpp"
+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"
+
+%struct.Foo = type { i32 (...)** }
+
+; Check that the vtable was not turned into an alias to a rewritten private
+; global.
+; CHECK: @_ZTV3Foo = dso_local unnamed_addr constant
+ at _ZTV3Foo = dso_local unnamed_addr constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* bitcast ({ i8*, i8* }* @_ZTI3Foo to i8*), i8* bitcast (i32 (%struct.Foo*)* @_ZN3Foo2f1Ev to i8*), i8* bitcast (i32 (%struct.Foo*)* @_ZN3Foo2f2Ev to i8*)] }, align 8, !type !0, !type !1, !type !2
+
+ at _ZTVN10__cxxabiv117__class_type_infoE = external dso_local global i8*
+ at _ZTS3Foo = dso_local constant [5 x i8] c"3Foo\00", align 1
+ at _ZTI3Foo = dso_local constant { i8*, i8* } { i8* bitcast (i8** getelementptr inbounds (i8*, i8** @_ZTVN10__cxxabiv117__class_type_infoE, i64 2) to i8*), i8* getelementptr inbounds ([5 x i8], [5 x i8]* @_ZTS3Foo, i32 0, i32 0) }, align 8
+ at b = dso_local local_unnamed_addr global %struct.Foo* null, align 8
+
+define dso_local i32 @main() local_unnamed_addr {
+entry:
+  %0 = load %struct.Foo*, %struct.Foo** @b, align 8
+  %1 = bitcast %struct.Foo* %0 to i32 (%struct.Foo*)***
+  %vtable.i = load i32 (%struct.Foo*)**, i32 (%struct.Foo*)*** %1, align 8
+  %2 = bitcast i32 (%struct.Foo*)** %vtable.i to i8*
+
+  ; Check that the type test was not lowered.
+  ; CHECK: tail call i1 @llvm.type.test
+  %3 = tail call i1 @llvm.type.test(i8* %2, metadata !"_ZTS3Foo")
+
+  tail call void @llvm.assume(i1 %3)
+  %4 = load i32 (%struct.Foo*)*, i32 (%struct.Foo*)** %vtable.i, align 8
+  %call.i = tail call i32 %4(%struct.Foo* nonnull dereferenceable(8) %0)
+  ret i32 %call.i
+}
+
+declare i1 @llvm.type.test(i8*, metadata)
+declare void @llvm.assume(i1 noundef)
+declare dso_local i32 @_ZN3Foo2f1Ev(%struct.Foo* nocapture nonnull readnone dereferenceable(8) %this) unnamed_addr
+declare dso_local i32 @_ZN3Foo2f2Ev(%struct.Foo* nocapture nonnull readnone dereferenceable(8) %this) unnamed_addr
+
+!0 = !{i64 16, !"_ZTS3Foo"}
+!1 = !{i64 16, !"_ZTSM3FooFivE.virtual"}
+!2 = !{i64 24, !"_ZTSM3FooFivE.virtual"}
Index: llvm/lib/Transforms/IPO/LowerTypeTests.cpp
===================================================================
--- llvm/lib/Transforms/IPO/LowerTypeTests.cpp
+++ llvm/lib/Transforms/IPO/LowerTypeTests.cpp
@@ -2058,6 +2058,24 @@
   if (TypeTestFunc) {
     for (const Use &U : TypeTestFunc->uses()) {
       auto CI = cast<CallInst>(U.getUser());
+      // If this type test is only used by llvm.assume instructions, it
+      // was used for whole program devirtualization, and is being kept
+      // for use by other optimization passes. We do not need or want to
+      // lower it here. We also don't want to rewrite any associated globals
+      // unnecessarily. These will be removed by a subsequent LTT invocation
+      // with the DropTypeTests flag set.
+      bool OnlyAssumeUses = !CI->use_empty();
+      for (auto CIU = CI->use_begin(), CIUE = CI->use_end(); CIU != CIUE;) {
+        if (auto *AssumeCI = dyn_cast<CallInst>((*CIU++).getUser())) {
+          Function *F = AssumeCI->getCalledFunction();
+          if (F && F->getIntrinsicID() == Intrinsic::assume)
+            continue;
+        }
+        OnlyAssumeUses = false;
+        break;
+      }
+      if (OnlyAssumeUses)
+        continue;
 
       auto TypeIdMDVal = dyn_cast<MetadataAsValue>(CI->getArgOperand(1));
       if (!TypeIdMDVal)


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