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Avoid PHI node re-allocation in loop copying

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duplicate_loop_body_to_header_edge redirects the original loop entry
edge to the loop copy header and the copied loop exit to the old
loop header.  But it does so in the order that requires temporary
space for an extra edge on the original loop header, causing
unnecessary re-allocations.  The following avoids this by swapping
the order of the redirects.

	* cfgloopmanip.cc (duplicate_loop_body_to_header_edge): When
	copying to the header edge first redirect the entry to the
	new loop and then the exit to the old to avoid PHI node
	re-allocation.
This commit is contained in:
Richard Biener 2025-01-08 15:12:30 +01:00 • committed by Richard Biener
parent 3b694271be
commit 1db025c67f
1 changed files with 1 additions and 1 deletions
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2
gcc/cfgloopmanip.cc
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@ -1447,9 +1447,9 @@ duplicate_loop_body_to_header_edge (class loop *loop, edge e,
}
else
{
redirect_edge_and_branch_force (e, new_bbs[0]);
redirect_edge_and_branch_force (new_spec_edges[SE_LATCH],
loop->header);
redirect_edge_and_branch_force (e, new_bbs[0]);
set_immediate_dominator (CDI_DOMINATORS, new_bbs[0], e->src);
e = new_spec_edges[SE_LATCH];
}