[llvm] Bail out jump threading on indirect branches (PR #103688)
via llvm-commits
llvm-commits at lists.llvm.org
Tue Aug 13 23:12:53 PDT 2024
https://github.com/hiraditya created https://github.com/llvm/llvm-project/pull/103688
The bug was introduced by https://github.com/llvm/llvm-project/pull/68473
>From cc2214cec7f3dd92c9718640495f9e39dd9ad48a Mon Sep 17 00:00:00 2001
From: AdityaK <hiraditya at msn.com>
Date: Tue, 13 Aug 2024 22:11:06 -0700
Subject: [PATCH] Bail out jump threading on indirect branches
The bug was introduced by https://github.com/llvm/llvm-project/pull/68473
---
llvm/lib/Transforms/Utils/Local.cpp | 7 +-
.../switch-branch-fold-indirectbr-102351.ll | 82 +++++++++++++++++++
2 files changed, 87 insertions(+), 2 deletions(-)
create mode 100644 llvm/test/Transforms/SimplifyCFG/switch-branch-fold-indirectbr-102351.ll
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index efb02fdec56d7e..4b37656d069bbd 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -868,6 +868,8 @@ CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ,
LLVM_DEBUG(dbgs() << "Looking to fold " << BB->getName() << " into "
<< Succ->getName() << "\n");
+ if (isa<IndirectBrInst>(Succ->getTerminator()))
+ return false;
// Shortcut, if there is only a single predecessor it must be BB and merging
// is always safe
if (Succ->getSinglePredecessor())
@@ -1029,11 +1031,12 @@ CanRedirectPredsOfEmptyBBToSucc(BasicBlock *BB, BasicBlock *Succ,
return false;
// Get single common predecessors of both BB and Succ
+ // TODO: Replace this with a proper `set intersect` algorithm
for (BasicBlock *SuccPred : SuccPreds) {
if (BBPreds.count(SuccPred)) {
+ CommonPred = SuccPred;
if (CommonPred)
return false;
- CommonPred = SuccPred;
}
}
@@ -1133,7 +1136,7 @@ bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
bool BBKillable = CanPropagatePredecessorsForPHIs(BB, Succ, BBPreds);
- // Even if we can not fold bB into Succ, we may be able to redirect the
+ // Even if we can not fold BB into Succ, we may be able to redirect the
// predecessors of BB to Succ.
bool BBPhisMergeable =
BBKillable ||
diff --git a/llvm/test/Transforms/SimplifyCFG/switch-branch-fold-indirectbr-102351.ll b/llvm/test/Transforms/SimplifyCFG/switch-branch-fold-indirectbr-102351.ll
new file mode 100644
index 00000000000000..a715c4f85859f8
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/switch-branch-fold-indirectbr-102351.ll
@@ -0,0 +1,82 @@
+; RUN: opt < %s -passes=simplifycfg -S | FileCheck %s
+
+; CHECK: switch i32 %state.0, label %sw.epilog
+; CHECK-NEXT: i32 0, label %sw.bb
+; CHECK-NEXT: i32 1, label %VM__OP_1
+; CHECK-NEXT: i32 2, label %sw.bb4
+
+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"
+
+ at .str = private unnamed_addr constant [23 x i8] c"OP_1:(instruction=%d)\0A\00", align 1
+ at .str.1 = private unnamed_addr constant [28 x i8] c"TERMINATE:(instruction=%d)\0A\00", align 1
+
+; Function Attrs: mustprogress norecurse uwtable
+define dso_local noundef i32 @main() #0 {
+entry:
+ %bytecode = alloca [2 x ptr], align 16
+ store ptr blockaddress(@main, %VM__OP_1), ptr %bytecode, align 16, !tbaa !5
+ %arrayidx1 = getelementptr inbounds [2 x ptr], ptr %bytecode, i64 0, i64 1
+ store ptr blockaddress(@main, %VM__TERMINATE), ptr %arrayidx1, align 8, !tbaa !5
+ br label %while.body
+
+while.body: ; preds = %entry, %sw.epilog
+ %state.0 = phi i32 [ 0, %entry ], [ %state.1, %sw.epilog ]
+ %index.0 = phi i32 [ 0, %entry ], [ %index.2, %sw.epilog ]
+ switch i32 %state.0, label %sw.epilog [
+ i32 0, label %sw.bb
+ i32 1, label %VM__OP_1
+ i32 2, label %sw.bb4
+ ]
+
+sw.bb: ; preds = %while.body
+ br label %indirectgoto
+
+VM__OP_1: ; preds = %while.body, %indirectgoto
+ %index.1 = phi i32 [ %index.3, %indirectgoto ], [ %index.0, %while.body ]
+ br label %sw.epilog
+
+sw.bb4: ; preds = %while.body
+ %call = call i32 (ptr, ...) @printf(ptr noundef nonnull dereferenceable(1) @.str, i32 noundef %index.0)
+ %inc = add nsw i32 %index.0, 1
+ br label %indirectgoto
+
+sw.epilog: ; preds = %while.body, %VM__OP_1
+ %state.1 = phi i32 [ %state.0, %while.body ], [ 2, %VM__OP_1 ]
+ %index.2 = phi i32 [ %index.0, %while.body ], [ %index.1, %VM__OP_1 ]
+ br label %while.body, !llvm.loop !9
+
+VM__TERMINATE: ; preds = %indirectgoto
+ %call7 = call i32 (ptr, ...) @printf(ptr noundef nonnull dereferenceable(1) @.str.1, i32 noundef %index.3)
+ ret i32 0
+
+indirectgoto: ; preds = %sw.bb4, %sw.bb
+ %index.3 = phi i32 [ %inc, %sw.bb4 ], [ %index.0, %sw.bb ]
+ %idxprom.pn = sext i32 %index.3 to i64
+ %indirect.goto.dest.in = getelementptr inbounds [2 x ptr], ptr %bytecode, i64 0, i64 %idxprom.pn
+ %indirect.goto.dest = load ptr, ptr %indirect.goto.dest.in, align 8, !tbaa !5
+ indirectbr ptr %indirect.goto.dest, [label %VM__OP_1, label %VM__TERMINATE]
+}
+declare i32 @printf(ptr noundef, ...) #1
+
+attributes #0 = { mustprogress norecurse uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+attributes #1 = { "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+
+!llvm.module.flags = !{!0, !1, !2, !3}
+!llvm.ident = !{!4}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{i32 8, !"PIC Level", i32 2}
+!2 = !{i32 7, !"PIE Level", i32 2}
+!3 = !{i32 7, !"uwtable", i32 2}
+!4 = !{!"clang version 18.0.0git (https://github.com/llvm/llvm-project.git 67782d2de5ea9c8653b8f0110237a3c355291c0e)"}
+!5 = !{!6, !6, i64 0}
+!6 = !{!"any pointer", !7, i64 0}
+!7 = !{!"omnipotent char", !8, i64 0}
+!8 = !{!"Simple C++ TBAA"}
+!9 = !{!10, !10, i64 0}
+!10 = !{!"int", !7, i64 0}
+!11 = distinct !{!11, !12, !13}
+!12 = !{!"llvm.loop.mustprogress"}
+!13 = !{!"llvm.loop.unroll.disable"}
+
More information about the llvm-commits
mailing list