[PATCH] D23586: [Coroutines] Part 8: Coroutine Frame Building algorithm

[Gor Nishanov via llvm-commits]

GorNishanov marked 5 inline comments as done.

================
Comment at: lib/Transforms/Coroutines/CoroFrame.cpp:479-480
@@ +478,4 @@
+
+  // TODO: Simplify PHINodes in the basic block to remove duplicate
+  // predecessors.
+
----------------
I do not think there is a correctness issue here. 
For the case like:

```
entry:
    ...
    br i1 %x label %a, label %a
    ...
a:
    phi [0 %entry], [0 %entry], [1 %loop]
```
With the code as is, we will create two identical edge blocks:
```
entry:
    ...
    br i1 %x label %a1, label %a2
    ...
a1:
    %a1.val = phi [0 %entry]
    br label %a
a2:
    %a2.val = phi [0 %entry]
    br label %a
a3:
    %a3.val = phi [1 %loop]
    br label %a
a:
    phi [%a1.val %a1], [%a2.val %a2],  [%a3.val %a3]
```

I added a TODO to tighten up PHI rewriting so that for identical predecessors we can share an edge block, so that the example above would look like:

```
entry:
    ...
    br i1 %x label %a1, label %a2
    ...
a1:
    %a1.val = phi [0 %entry]
    br label %a
a2:
    %a2.val = phi [1 %loop]
    br label %a
a:
    phi [%a1.val %a1], [%a2.val %a2]
```



https://reviews.llvm.org/D23586