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calls in nothrow functions can be marked nothrow even if the callee

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is not known to be nothrow.  This allows readnone/readonly functions
to be deleted even if we don't know whether the callee can throw.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71676 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-05-13 17:39:14 +00:00
parent ad6585b021
commit aab6ec49d2
2 changed files with 18 additions and 0 deletions
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10
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -9578,6 +9578,16 @@ Instruction *InstCombiner::SimplifyMemSet(MemSetInst *MI) {
/// the heavy lifting.
///
Instruction *InstCombiner::visitCallInst(CallInst &CI) {
// If the caller function is nounwind, mark the call as nounwind, even if the
// callee isn't.
if (CI.getParent()->getParent()->doesNotThrow() &&
!CI.doesNotThrow()) {
CI.setDoesNotThrow();
return &CI;
}
IntrinsicInst *II = dyn_cast<IntrinsicInst>(&CI);
if (!II) return visitCallSite(&CI);

8
test/Transforms/InstCombine/nothrow.ll Normal file
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@ -0,0 +1,8 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep call
; rdar://6880732
declare double @t1(i32) readonly
define void @t2() nounwind {
call double @t1(i32 42) ;; dead call even though callee is not nothrow.
ret void
}