[PATCH] D11819: [RewriteStatepointsForGC] Avoid using unrelocated pointers after safepoints

[Sanjoy Das via llvm-commits]

sanjoy requested changes to this revision.
This revision now requires changes to proceed.

================
Comment at: lib/Transforms/Scalar/RewriteStatepointsForGC.cpp:2424
@@ +2423,3 @@
+        return dyn_cast<Instruction>(BI->getCondition());
+    if (auto *SI = dyn_cast<SwitchInst>(TI))
+      return dyn_cast<Instruction>(SI->getCondition());
----------------
A `switch` on an `icmp` is equivalent to a `br`; perhaps we should just teach LLVM to transform


```
  %c = icmp slt i32 %x, 0
  switch i1 %c, label %def [ i1 0, label %f
                             i1 1, label %t ]
```

to

```
  %c = icmp slt i32 %x, 0
  br i1 %c, label %t, label %f
```
 
so that we don't have to deal with `switch` separately here?

(Right now LLVM does not do the said transform, which surprised me).


If you remove the `switch` case (pun intended!) here then you should be able to use a simple expression from PatternMatch.h to match a conditional `br` on an `icmp`.

================
Comment at: lib/Transforms/Scalar/RewriteStatepointsForGC.cpp:2426
@@ +2425,3 @@
+      return dyn_cast<Instruction>(SI->getCondition());
+    return (Instruction*)nullptr;
+  };
----------------
I'd prefer typing the lambda with an explicit type, like

```
[](TerminatorInst *TI) -> Instruction * {
...
```



http://reviews.llvm.org/D11819