About the is_gimple_min_invariant predicate

Eric Botcazou ebotcazou@adacore.com
Thu Jul 5 15:12:00 GMT 2007

> We never insert expressions for FRE, and the replacement we do will
> only replace the entire RHS with an SSA_NAME or a constant.

The problem is precisely that the expression is deemed a constant:

	  /* Setting value numbers to constants will occasionally
	     screw up phi congruence because constants are not
	     uniquely associated with a single ssa name that can be
	     looked up.  */
	  if (simplified && is_gimple_min_invariant (simplified)
	      && TREE_CODE (lhs) == SSA_NAME
	      && simplified != rhs)
	      VN_INFO (lhs)->expr = simplified;
	      VN_INFO (lhs)->has_constants = true;
	      changed = set_ssa_val_to (lhs, simplified);
	      goto done;

Eric Botcazou

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