From 5e3d770fccd3639773b69bdd8671a03fd80e3dc1 Mon Sep 17 00:00:00 2001
From: TB Schardl <neboat@mit.edu>
Date: Fri, 20 Oct 2023 00:15:22 +0000
Subject: [PATCH] [InstCombine] Fix removal of adjacent tapir.runtime.start and
 tapir.runtime.end calls.

---
 .../InstCombine/InstCombineCalls.cpp          |  4 +-
 llvm/test/Transforms/Tapir/empty-scope.ll     | 49 +++++++++++++++++++
 2 files changed, 51 insertions(+), 2 deletions(-)
 create mode 100644 llvm/test/Transforms/Tapir/empty-scope.ll

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 9df30997b243..3a9de1321d23 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -2440,8 +2440,8 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
     BasicBlock::iterator Iter(CI);
     while (++Iter != CI.getParent()->end()) {
       if (isTapirIntrinsic(Intrinsic::tapir_runtime_end, &*Iter, &CI)) {
-        eraseInstFromFunction(CI);
-        return eraseInstFromFunction(*Iter);
+        eraseInstFromFunction(*Iter);
+        return eraseInstFromFunction(CI);
       }
       if (isa<CallBase>(&*Iter) && !isa<DbgInfoIntrinsic>(&*Iter))
         // We found a nontrivial call.  Give up.
diff --git a/llvm/test/Transforms/Tapir/empty-scope.ll b/llvm/test/Transforms/Tapir/empty-scope.ll
new file mode 100644
index 000000000000..ae7117b00e55
--- /dev/null
+++ b/llvm/test/Transforms/Tapir/empty-scope.ll
@@ -0,0 +1,49 @@
+; Check that instcombine properly removes adjacent tapir.runtime
+; calls.
+;
+; RUN: opt < %s -passes="instcombine" -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"
+
+; Function Attrs: nounwind uwtable
+define dso_local i32 @main(i32 noundef %argc, ptr noundef %argv) #0 {
+entry:
+  %retval = alloca i32, align 4
+  %argc.addr = alloca i32, align 4
+  %argv.addr = alloca ptr, align 8
+  store i32 0, ptr %retval, align 4
+  store i32 %argc, ptr %argc.addr, align 4, !tbaa !5
+  store ptr %argv, ptr %argv.addr, align 8, !tbaa !9
+  %0 = call token @llvm.tapir.runtime.start()
+  call void @llvm.tapir.runtime.end(token %0)
+  ret i32 0
+}
+
+; CHECK: define {{.*}}i32 @main(
+; CHECK-NOT: call token @llvm.tapir.runtime.start
+; CHECK-NOT: call void @llvm.tapir.runtime.end
+; CHECK: ret
+
+; Function Attrs: nounwind willreturn memory(argmem: readwrite)
+declare token @llvm.tapir.runtime.start() #1
+
+; Function Attrs: nounwind willreturn memory(argmem: readwrite)
+declare void @llvm.tapir.runtime.end(token) #1
+
+attributes #0 = { nounwind uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+attributes #1 = { nounwind willreturn memory(argmem: readwrite) }
+
+!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 16.0.6 (git@github.com:OpenCilk/opencilk-project.git ca9e0f93cdcefe84809f3ddd9c61363b76a1a271)"}
+!5 = !{!6, !6, i64 0}
+!6 = !{!"int", !7, i64 0}
+!7 = !{!"omnipotent char", !8, i64 0}
+!8 = !{!"Simple C/C++ TBAA"}
+!9 = !{!10, !10, i64 0}
+!10 = !{!"any pointer", !7, i64 0}