[PATCH] D74691: [Attributor] Detect possibly unbounded cycles in functions

[Johannes Doerfert via Phabricator via llvm-commits]

jdoerfert added a comment.

I haven't read all the comments but the code looks good with one problem, see below.



================
Comment at: llvm/lib/Transforms/IPO/Attributor.cpp:2380
+  if (!SE || !LI)
+    NoAnalysis = true;
 
----------------
Nit: `bool NoAnalysis = !SE || !LI;`



================
Comment at: llvm/lib/Transforms/IPO/Attributor.cpp:2394
+        Loop *L = LI->getLoopFor(BB);
+        if (L && !SE->getSmallConstantMaxTripCount(L))
+          return true;
----------------
```
if (!L || !SE->getSmallConstantMaxTripCount(L))
  return true;
```

You ignore non-loop cycles otherwise. Please add a non-loop cycle test case, aka. irreducible control flow test case.

Here is a piece of C that should help create the test:
```
if (foo())
  goto entry1;
else
  goto entry2;

entry1:
  if (foo())
    goto exit;
  else
    goto entry2;
entry2:
  if (foo())
    goto exit;
  else
    goto entry1;
exit:
  return;
```



Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D74691