[PATCH] Fix PR17168 (DAG scheduler inserts DBG_VALUE before PHI with fast-isel)

[Bill Wendling]

LGTM, but man, that test case is horrible!

-bw

On Oct 2, 2013, at 1:10 PM, Bill Schmidt <wschmidt at linux.vnet.ibm.com> wrote:

> PR17168 describes a test case that fails when compiling for debug with
> fast-isel.  Investigation showed that the test was failing because a
> DBG_VALUE machine instruction was placed prior to a PHI.
> 
> For this problem to occur requires the following:
> * Compile for debug
> * Compile with fast-isel
> * In a block B, fast-isel must partially succeed before punting to DAG-isel
> * B must start with a PHI
> * The first unhandled node in the DAG must not generate a machine instruction
> * A debug value with an order less than that of that first node exists
> 
> When all of these circumstances apply, the existing test that an
> instruction was not inserted won't fire.  Currently it tests whether the
> block is empty, or whether the last instruction generated is a phi.
> When fast-isel has partially succeeded, the last instruction generated
> will not be a phi.  Instead, we need to check whether the current insert
> position is immediately following a phi.  This patch adds that check,
> and adds the test case from the PR as a regression test.
> 
> Tested on powerpc64-unknown-linux-gnu with no regressions.  Is this ok
> to commit?
> 
> Thanks,
> Bill
> 
> <pr17168-2013-10-02.patch>_______________________________________________
> llvm-commits mailing list
> llvm-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits