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Revert 94937 and move the noreturn check to codegen.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95198 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2010-02-03 03:55:59 +00:00
parent 2e235a826d
commit febc81680c
5 changed files with 25 additions and 20 deletions
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9
lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
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@ -4205,8 +4205,13 @@ isInTailCallPosition(CallSite CS, Attributes CalleeRetAttr,
const ReturnInst *Ret = dyn_cast<ReturnInst>(Term); const ReturnInst *Ret = dyn_cast<ReturnInst>(Term);
const Function *F = ExitBB->getParent(); const Function *F = ExitBB->getParent();
// The block must end in a return statement or an unreachable. // The block must end in a return statement.
if (!Ret && !isa<UnreachableInst>(Term)) return false; // 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;
// Unless we are explicitly forcing tailcall optimization do not tailcall if // Unless we are explicitly forcing tailcall optimization do not tailcall if
// the called function is bitcast'ed. The analysis may not be entirely // the called function is bitcast'ed. The analysis may not be entirely

9
lib/Transforms/Scalar/TailRecursionElimination.cpp
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@ -184,11 +184,10 @@ bool TailCallElim::runOnFunction(Function &F) {
if (!FunctionContainsEscapingAllocas) if (!FunctionContainsEscapingAllocas)
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
if (CallInst *CI = dyn_cast<CallInst>(I)) if (CallInst *CI = dyn_cast<CallInst>(I)) {
if (!CI->doesNotReturn()) { CI->setTailCall();
CI->setTailCall(); MadeChange = true;
MadeChange = true; }
}
return MadeChange; return MadeChange;
} }

2
test/CodeGen/X86/tailcall1.ll
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@ -1,4 +1,4 @@
; RUN: llc < %s -march=x86 -tailcallopt | grep TAILCALL | count 5 ; RUN: llc < %s -march=x86 -tailcallopt | grep TAILCALL | count 4
declare fastcc i32 @tailcallee(i32 %a1, i32 %a2, i32 %a3, i32 %a4) declare fastcc i32 @tailcallee(i32 %a1, i32 %a2, i32 %a3, i32 %a4)

13
test/CodeGen/X86/tailcall2.ll
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@ -127,3 +127,16 @@ entry:
%1 = tail call signext i16 %0(i32 0) nounwind %1 = tail call signext i16 %0(i32 0) nounwind
ret i16 %1 ret i16 %1
} }
define void @t10() nounwind ssp {
entry:
; 32: t10:
; 32: call
; 64: t10:
; 64: callq
%0 = tail call i32 @foo4() noreturn nounwind
unreachable
}
declare i32 @foo4()

12
test/Transforms/TailCallElim/no-return-calls.ll
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@ -1,12 +0,0 @@
; RUN: opt < %s -tailcallelim -S | FileCheck %s
define void @t() nounwind ssp {
entry:
; CHECK: entry:
; CHECK: %0 = call i32 @foo()
; CHECK: ret void
%0 = call i32 @foo() nounwind noreturn
ret void
}
declare i32 @foo()