Fix a bug in mayHaveSideEffects. Functions that do not return are now considered as instructions with side effects.
rdar://13227456
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175553 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/llvm/IR/Instruction.h b/include/llvm/IR/Instruction.h
index e5e5f96..5721d8f 100644
--- a/include/llvm/IR/Instruction.h
+++ b/include/llvm/IR/Instruction.h
@@ -309,6 +309,12 @@
///
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 @@
/// 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
diff --git a/lib/IR/Instruction.cpp b/lib/IR/Instruction.cpp
index 42df5d7..2b5a0b3 100644
--- a/lib/IR/Instruction.cpp
+++ b/lib/IR/Instruction.cpp
@@ -455,14 +455,18 @@
}
}
-/// 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
diff --git a/test/Transforms/FunctionAttrs/noreturn.ll b/test/Transforms/FunctionAttrs/noreturn.ll
new file mode 100644
index 0000000..470ebcb
--- /dev/null
+++ b/test/Transforms/FunctionAttrs/noreturn.ll
@@ -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
+}
+