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tree-object-size: Deterministic SSA generation [PR123351]

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The order of evaluation of function arguments is unspecified in C++.
The function object_sizes_set_temp called object_sizes_set with two
calls to make_ssa_name() as arguments.  Since make_ssa_name() has the
side effect of incrementing the global SSA version counter, different
architectures of the same compiler evaluated these calls in different
orders.

This resulted in non-deterministic SSA version numbering between
x86_64 and aarch64 hosts during cross-compilation, leading to
divergent object files.

Sequencing the calls into separate statements ensures deterministic
evaluation order.

2026-01-06  Jakub Jelinek  <jakub@redhat.com>
	    Marco Falke  <falke.marco@gmail.com>

	PR tree-optimization/123351
	* tree-object-size.cc (object_sizes_set_temp): Separate calls to
	make_ssa_name to ensure deterministic execution order.
This commit is contained in:
Jakub Jelinek
2026-01-06 08:36:20 +01:00
committed by Jakub Jelinek
parent e32c3fb431
commit c6085ca0ed
1 changed files with 5 additions and 3 deletions
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8
gcc/tree-object-size.cc
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@@ -322,9 +322,11 @@ object_sizes_set_temp (struct object_size_info *osi, unsigned varno)
tree val = object_sizes_get (osi, varno);
if (size_initval_p (val, osi->object_size_type))
object_sizes_set (osi, varno,
make_ssa_name (sizetype),
make_ssa_name (sizetype));
{
val = make_ssa_name (sizetype);
tree wholeval = make_ssa_name (sizetype);
object_sizes_set (osi, varno, val, wholeval);
}
}
/* Initialize OFFSET_LIMIT variable. */