This fixes#147063.
I tried to fix this issue in more general way in
https://github.com/llvm/llvm-project/pull/147091 but the reviewer
suggested to fix the locations which are causing this issue. So this is
a more targeted approach.
The `restoreIP` is frequently used in the `OMPIRBuilder` to change the
insert position. This function eventually calls
`SetInsertPoint(BasicBlock *TheBB, BasicBlock::iterator IP)`. This
function updates the insert point and the debug location. But if the
`IP` is pointing to the end of the `TheBB`, then the debug location is
not updated and we could have a mismatch between insert point and the
debug location.
The problem can occur in 2 different code patterns.
This code below shows the first scenario.
```
1. auto curPos = builder.saveIP();
2. builder.restoreIP(/* some new pos */);
3. // generate some code
4. builder.restoreIP(curPos);
```
If `curPos` points to the end of basic block, we could have a problem.
But it is easy one to handle as we have the location before hand and can
save the correct debug location before 2 and then restore it after 3.
This can be done either manually or using the `llvm::InsertPointGuard`
as shown below.
```
// manual approach
auto curPos = builder.saveIP();
llvm::DebugLoc DbgLoc = builder.getCurrentDebugLocation();
builder.restoreIP(/* some new pos */);
// generate some code
builder.SetCurrentDebugLocation(DbgLoc);
builder.restoreIP(curPos);
{
// using InsertPointGuard
llvm::InsertPointGuard IPG(builder);
builder.restoreIP(/* some new pos */);
// generate some code
}
```
This PR fixes one problematic case using the manual approach.
For the 2nd scenario, look at the code below.
```
1. void fn(InsertPointTy allocIP, InsertPointTy codegenIP) {
2. builder.setInsertPoint(allocIP);
3. // generate some alloca
4. builder.setInsertPoint(codegenIP);
5. }
```
The `fn` can be called from anywhere and we can't assume the debug
location of the builder is valid at the start of the function. So if 4
does not update the debug location because the `codegenIP` points at the
end of the block, the rest of the code can end up using the debug
location of the `allocaIP`. Unlike the first case, we don't have a debug
location that we can save before hand and restore afterwards.
The solution here is to use the location of the last instruction in that
block. I have added a wrapper function over `restoreIP` that could be
called for such cases. This PR uses it to fix one problematic case.
049953fe8d