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Fix a bug in mayHaveSideEffects. Functions that do not return are now considered as instructions with side effects.

Browse Source 
rdar://13227456



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175553 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nadav Rotem 2013-02-19 20:02:09 +00:00
parent a175396816
commit 03544ec2a4
3 changed files with 31 additions and 3 deletions
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8
include/llvm/IR/Instruction.h
View File

@ -309,6 +309,12 @@ public:
///
bool mayThrow() const;
/// mayReturn - Return true if this is a function that may return.
/// this is true for all normal instructions. The only exception
/// is functions that are marked with the 'noreturn' attribute.
///
bool mayReturn() const;
/// mayHaveSideEffects - Return true if the instruction may have side effects.
///
/// Note that this does not consider malloc and alloca to have side
@ -316,7 +322,7 @@ public:
/// instructions which don't used the returned value. For cases where this
/// matters, isSafeToSpeculativelyExecute may be more appropriate.
bool mayHaveSideEffects() const {
return mayWriteToMemory() || mayThrow();
return mayWriteToMemory() || mayThrow() || !mayReturn();
}
/// clone() - Create a copy of 'this' instruction that is identical in all

8
lib/IR/Instruction.cpp
View File

@ -455,14 +455,18 @@ bool Instruction::mayWriteToMemory() const {
}
}
/// mayThrow - Return true if this instruction may throw an exception.
///
bool Instruction::mayThrow() const {
if (const CallInst *CI = dyn_cast<CallInst>(this))
return !CI->doesNotThrow();
return isa<ResumeInst>(this);
}
bool Instruction::mayReturn() const {
if (const CallInst *CI = dyn_cast<CallInst>(this))
return !CI->doesNotReturn();
return true;
}
/// isAssociative - Return true if the instruction is associative:
///
/// Associative operators satisfy: x op (y op z) === (x op y) op z

18
test/Transforms/FunctionAttrs/noreturn.ll Normal file
View File

@ -0,0 +1,18 @@
; RUN: opt < %s -functionattrs -instcombine -S | FileCheck %s
define void @endless_loop() noreturn nounwind readnone ssp uwtable {
entry:
br label %while.body
while.body:
br label %while.body
}
;CHECK: @main
;CHECK: endless_loop
;CHECK: ret
define i32 @main() noreturn nounwind ssp uwtable {
entry:
tail call void @endless_loop()
unreachable
}