Fix PR48389: ICE in make_edges

[Jeff Law]

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On 04/08/11 07:33, Michael Matz wrote:
> Hi,
> 
> the problem is that some initializers expand to loops.  If such 
> initializers are inserted on edges we have looping control flow on them.  
> Even if we have no loops, but normal control flow on them (which can 
> happen in other situations) we still forget to initialize JUMP_LABEL on 
> them leading to potential problems downstream (no idea why we never hit 
> any real problems until we had loops on edges, this problem is latent 
> since expand from SSA form).
> 
> So, we have to initialize the jump labels somewhen.  The obvious idea to 
> simply call rebuild_jump_labels after all insertions are done doesn't 
> work, because the jump labels are already needed for splitting edges (for 
> patching the jump insns), which insertion might cause.
> 
> So, instead than this I've added another interface to initialize jump 
> labels for a non-main chain of instructions (in fact it's the same as with 
> the main chain, merely not diddling with the forced_labels list).
> 
> Fixes the testcase, gcc dg.exp is clean, I'm currently regstrapping this 
> on x86_64-linux.  Okay if that passes?
> 
> 
> Ciao,
> Michael.
> 	PR middle-end/48389
> 	* jump.c (rebuild_jump_labels_1, rebuild_jump_labels_chain): New
> 	functions.
> 	(rebuild_jump_labels): Call rebuild_jump_labels_1.
> 	* rtl.h (rebuild_jump_labels_chain): Declare.
> 	* cfgexpand.c (expand_gimple_basic_block): Use PAT_VAR_LOCATION_LOC,
> 	not INSN_VAR_LOCATION_LOC.
> 	(gimple_expand_cfg): Initialize JUMP_LABEL also on insn inserted
> 	on edges.
> 
> testsuite/
> 	* gcc.target/i386/pr48389.c: New test.
I'd pondered a similar approach, but hadn't tried an implementation.
Good to see it wasn't hard to make it work.  I like this better than
Steven's approach.  OK by me.

Jeff
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