From daf21289b6de229e22a853a0a140682e039d3b8e Mon Sep 17 00:00:00 2001
From: Sanjoy Das <sanjoy@playingwithpointers.com>
Date: Mon, 7 Nov 2016 21:01:49 +0000
Subject: [PATCH] Avoid tail recursion elimination across calls with operand
 bundles

Summary:
In some specific scenarios with well understood operand bundle types
(like `"deopt"`) it may be possible to go ahead and convert recursion to
iteration, but TailRecursionElimination does not have that logic today
so avoid doing the right thing for now.

I need some input on whether `"funclet"` operand bundles should also
block tail recursion elimination.  If not, I'll allow TRE across calls
with `"funclet"` operand bundles and add a test case.

Reviewers: rnk, majnemer, nlewycky, ahatanak

Subscribers: mcrosier, llvm-commits

Differential Revision: https://reviews.llvm.org/D26270

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@286147 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../Scalar/TailRecursionElimination.cpp       |  3 +-
 test/Transforms/TailCallElim/deopt-bundle.ll  | 57 +++++++++++++++++++
 2 files changed, 59 insertions(+), 1 deletion(-)
 create mode 100644 test/Transforms/TailCallElim/deopt-bundle.ll

diff --git a/lib/Transforms/Scalar/TailRecursionElimination.cpp b/lib/Transforms/Scalar/TailRecursionElimination.cpp
index 16c88270a84..2c0294ccc38 100644
--- a/lib/Transforms/Scalar/TailRecursionElimination.cpp
+++ b/lib/Transforms/Scalar/TailRecursionElimination.cpp
@@ -236,7 +236,7 @@ static bool markTails(Function &F, bool &AllCallsAreTailCalls) {
       if (!CI || CI->isTailCall())
         continue;
 
-      bool IsNoTail = CI->isNoTailCall();
+      bool IsNoTail = CI->isNoTailCall() || CI->hasOperandBundles();
 
       if (!IsNoTail && CI->doesNotAccessMemory()) {
         // A call to a readnone function whose arguments are all things computed
@@ -256,6 +256,7 @@ static bool markTails(Function &F, bool &AllCallsAreTailCalls) {
           SafeToTail = false;
           break;
         }
+        SafeToTail &= CI->hasOperandBundles();
         if (SafeToTail) {
           emitOptimizationRemark(
               F.getContext(), "tailcallelim", F, CI->getDebugLoc(),
diff --git a/test/Transforms/TailCallElim/deopt-bundle.ll b/test/Transforms/TailCallElim/deopt-bundle.ll
new file mode 100644
index 00000000000..a98c47e9e6f
--- /dev/null
+++ b/test/Transforms/TailCallElim/deopt-bundle.ll
@@ -0,0 +1,57 @@
+; RUN: opt < %s -tailcallelim -S | FileCheck %s
+
+define i32 @f_1(i32 %x) {
+; CHECK-LABEL: @f_1(
+wentry:
+  %cond = icmp ugt i32 %x, 0
+  br i1 %cond, label %return, label %body
+
+body:
+; CHECK: body:
+; CHECK: call i32 @f_1(i32 %y) [ "deopt"() ]
+  %y = add i32 %x, 1
+  %tmp = call i32 @f_1(i32 %y) [ "deopt"() ]
+  ret i32 0
+
+return:
+  ret i32 1
+}
+
+define i32 @f_2(i32 %x) {
+; CHECK-LABEL: @f_2
+
+entry:
+  %cond = icmp ugt i32 %x, 0
+  br i1 %cond, label %return, label %body
+
+body:
+; CHECK: body:
+; CHECK: call i32 @f_2(i32 %y) [ "unknown"() ]
+  %y = add i32 %x, 1
+  %tmp = call i32 @f_2(i32 %y) [ "unknown"() ]
+  ret i32 0
+
+return:
+  ret i32 1
+}
+
+declare void @func()
+
+define void @f_3(i1 %B) personality i8 42 {
+; CHECK-LABEL: @f_3(
+entry:
+  invoke void @func()
+          to label %exit unwind label %merge
+merge:
+  %cs1 = catchswitch within none [label %catch] unwind to caller
+
+catch:
+; CHECK: catch:
+; CHECK: call void @f_3(i1 %B) [ "funclet"(token %cp) ]
+  %cp = catchpad within %cs1 []
+  call void @f_3(i1 %B) [ "funclet"(token %cp) ]
+  ret void
+
+exit:
+  ret void
+}
-- 
2.40.0