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authorDan Gohman <gohman@apple.com>2010-02-08 20:34:14 +0000
committerDan Gohman <gohman@apple.com>2010-02-08 20:34:14 +0000
commitc2e93b255e120f066ad8c16b0593b05f7e9f3d19 (patch)
treef41aee4ef660f15060d337608f1a26849f39aec0
parent1797ed50f488f2030f9f9a0ac7426262abf5220a (diff)
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In guaranteed tailcall mode, don't decline the tailcall optimization
for blocks ending in "unreachable". git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95565 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r--lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp17
-rw-r--r--test/CodeGen/X86/tailcall1.ll5
2 files changed, 14 insertions, 8 deletions
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index cf342c7..93ae043 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -4205,13 +4205,16 @@ isInTailCallPosition(CallSite CS, Attributes CalleeRetAttr,
const ReturnInst *Ret = dyn_cast<ReturnInst>(Term);
const Function *F = ExitBB->getParent();
- // The block must end in a return statement.
- // FIXME: Disallow tailcall if the block ends in an unreachable for now.
- // The way tailcall optimization is currently implemented means it will
- // add an epilogue followed by a jump. That is not profitable. Also, if
- // the callee is a special function (e.g. longjmp on x86), it can end up
- // causing miscompilation that has not been fully understood.
- if (!Ret) return false;
+ // The block must end in a return statement or unreachable.
+ //
+ // FIXME: Decline tailcall if it's not guaranteed and if the block ends in
+ // an unreachable, for now. The way tailcall optimization is currently
+ // implemented means it will add an epilogue followed by a jump. That is
+ // not profitable. Also, if the callee is a special function (e.g.
+ // longjmp on x86), it can end up causing miscompilation that has not
+ // been fully understood.
+ if (!Ret &&
+ (!GuaranteedTailCallOpt || !isa<UnreachableInst>(Term))) return false;
// If I will have a chain, make sure no other instruction that will have a
// chain interposes between I and the return.
diff --git a/test/CodeGen/X86/tailcall1.ll b/test/CodeGen/X86/tailcall1.ll
index d08919e..f7ff5d5 100644
--- a/test/CodeGen/X86/tailcall1.ll
+++ b/test/CodeGen/X86/tailcall1.ll
@@ -1,4 +1,7 @@
-; RUN: llc < %s -march=x86 -tailcallopt | grep TAILCALL | count 4
+; RUN: llc < %s -march=x86 -tailcallopt | grep TAILCALL | count 5
+
+; With -tailcallopt, CodeGen guarantees a tail call optimization
+; for all of these.
declare fastcc i32 @tailcallee(i32 %a1, i32 %a2, i32 %a3, i32 %a4)