[PATCH] D22630: Loop rotation

[Eli Friedman via llvm-commits]

eli.friedman added inline comments.

================
Comment at: llvm/lib/Transforms/Scalar/LoopRotation.cpp:431
@@ +430,3 @@
+    DEBUG(dbgs() << "\nSplitting the edge of Loop:"; L->dumpVerbose(););
+    LoopLatch = SplitEdge(LoopLatch, L->getHeader(), DT, LI);
+  }
----------------
sebpop wrote:
> hiraditya wrote:
> > eli.friedman wrote:
> > > The loop latch could be an indirectbr.
> > I'll fix this, thanks.
> I have the impression that the loop analysis will not find a natural loop if the edge from the latch to the header is an indirect branch.
> Are you sure this is possible?  Do you have a test-case where we recognize a loop with an indirect branch for the latch edge?
indirectbr loop in C:

    int g(), h(), z();
    int f() {
        static void* x[] = {&&F, &&G, &&H};
        F: 
        goto *x[z()];
        
        G: return g();
        H: return h();
    }

`clang -x c - -o - -S -O2 -emit-llvm | opt -analyze -loops` gives:

    Printing analysis 'Natural Loop Information' for function 'f':
    Loop at depth 1 containing: %F<header><latch><exiting>


https://reviews.llvm.org/D22630