[CodeGen/Analysis] Intrinsic llvm.assume should not block tail call optimization

In function Analysis.cpp:isInTailCallPosition, instructions between call and ret are checked to see if they block tail call optimization. If an instruction is an intrinsic call, only llvm.lifetime_end is allowed and other intrinsic functions block tail call. When compiling tcmalloc, we found llvm.assume between a hot function call and ret, it blocks the optimization. But llvm.assume doesn't generate instructions, it should not block tail call.

Differential Revision: https://reviews.llvm.org/D66096

llvm-svn: 369125

1 files changed, 4 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/Analysis.cpp b/llvm/lib/CodeGen/Analysis.cpp
index e72938ba9be..f1bbb341df1 100644
--- a/llvm/lib/CodeGen/Analysis.cpp
+++ b/llvm/lib/CodeGen/Analysis.cpp
@@ -536,9 +536,11 @@ bool llvm::isInTailCallPosition(ImmutableCallSite CS, const TargetMachine &TM) {
       // Debug info intrinsics do not get in the way of tail call optimization.
       if (isa<DbgInfoIntrinsic>(BBI))
         continue;
-      // A lifetime end intrinsic should not stop tail call optimization.
+      // A lifetime end or assume intrinsic should not stop tail call
+      // optimization.
       if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI))
-        if (II->getIntrinsicID() == Intrinsic::lifetime_end)
+        if (II->getIntrinsicID() == Intrinsic::lifetime_end ||
+            II->getIntrinsicID() == Intrinsic::assume)
           continue;
       if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
           !isSafeToSpeculativelyExecute(&*BBI))