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re PR tree-optimization/61515 (Extremely long compile time for generated code)

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PR tree-optimization/61515
	* tree-ssa-threadedge.c (invalidate_equivalences): Walk the unwinding stack
	rather than looking at ever SSA_NAME's value.

From-SVN: r217239
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Jeff Law 2014-11-07 15:55:00 -07:00 committed by Jeff Law
parent 382ad5ce1b
commit f38ce9361f
2 changed files with 35 additions and 4 deletions
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gcc/ChangeLog
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@ -1,3 +1,9 @@
2014-11-07 Jeff Law <law@redhat.com>
PR tree-optimization/61515
* tree-ssa-threadedge.c (invalidate_equivalences): Walk the unwinding stack
rather than looking at ever SSA_NAME's value.
2014-11-07 Richard Biener <rguenther@suse.de>
PR tree-optimization/63605

33
gcc/tree-ssa-threadedge.c
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@ -290,15 +290,40 @@ fold_assignment_stmt (gimple stmt)
}
/* A new value has been assigned to LHS. If necessary, invalidate any
equivalences that are no longer valid. */
equivalences that are no longer valid. This includes invaliding
LHS and any objects that are currently equivalent to LHS.
Finding the objects that are currently marked as equivalent to LHS
is a bit tricky. We could walk the ssa names and see if any have
SSA_NAME_VALUE that is the same as LHS. That's expensive.
However, it's far more efficient to look at the unwinding stack as
that will have all context sensitive equivalences which are the only
ones that we really have to worry about here. */
static void
invalidate_equivalences (tree lhs, vec<tree> *stack)
{
for (unsigned int i = 1; i < num_ssa_names; i++)
if (ssa_name (i) && SSA_NAME_VALUE (ssa_name (i)) == lhs)
record_temporary_equivalence (ssa_name (i), NULL_TREE, stack);
/* The stack is an unwinding stack. If the current element is NULL
then it's a "stop unwinding" marker. Else the current marker is
the SSA_NAME with an equivalence and the prior entry in the stack
is what the current element is equivalent to. */
for (int i = stack->length() - 1; i >= 0; i--)
{
/* Ignore the stop unwinding markers. */
if ((*stack)[i] == NULL)
continue;
/* We want to check the current value of stack[i] to see if
it matches LHS. If so, then invalidate. */
if (SSA_NAME_VALUE ((*stack)[i]) == lhs)
record_temporary_equivalence ((*stack)[i], NULL_TREE, stack);
/* Remember, we're dealing with two elements in this case. */
i--;
}
/* And invalidate any known value for LHS itself. */
if (SSA_NAME_VALUE (lhs))
record_temporary_equivalence (lhs, NULL_TREE, stack);
}