From cc9e6c45785444b8c4a89b238ce244115a206fc3 Mon Sep 17 00:00:00 2001
From: Massimiliano Culpo <massimiliano.culpo@gmail.com>
Date: Wed, 8 Mar 2023 11:34:37 +0100
Subject: [PATCH] Emit facts for target compatibility directly

This is just a simplification, and it doesn't seem to
affect performance in any way.
---
 lib/spack/spack/solver/asp.py        | 10 ++++++----
 lib/spack/spack/solver/concretize.lp | 11 -----------
 2 files changed, 6 insertions(+), 15 deletions(-)

diff --git a/lib/spack/spack/solver/asp.py b/lib/spack/spack/solver/asp.py
index 670dcf6ef93..b910ee0d9b0 100644
--- a/lib/spack/spack/solver/asp.py
+++ b/lib/spack/spack/solver/asp.py
@@ -1820,8 +1820,10 @@ def target_defaults(self, specs):
         for target in candidate_targets:
             self.gen.fact(fn.target(target.name))
             self.gen.fact(fn.target_family(target.name, target.family.name))
-            for parent in sorted(target.parents):
-                self.gen.fact(fn.target_parent(target.name, parent.name))
+            self.gen.fact(fn.target_compatible(target.name, target.name))
+            # Code for ancestor can run on target
+            for ancestor in target.ancestors:
+                self.gen.fact(fn.target_compatible(target.name, ancestor.name))
 
             # prefer best possible targets; weight others poorly so
             # they're not used unless set explicitly
@@ -1832,10 +1834,10 @@ def target_defaults(self, specs):
                 i += 1
             else:
                 self.default_targets.append((100, target.name))
-
-            self.default_targets = list(sorted(set(self.default_targets)))
             self.gen.newline()
 
+        self.default_targets = list(sorted(set(self.default_targets)))
+
     def virtual_providers(self):
         self.gen.h2("Virtual providers")
         msg = (
diff --git a/lib/spack/spack/solver/concretize.lp b/lib/spack/spack/solver/concretize.lp
index a71631aa116..2ec997fe8b2 100644
--- a/lib/spack/spack/solver/concretize.lp
+++ b/lib/spack/spack/solver/concretize.lp
@@ -816,18 +816,7 @@ node_target_compatible(Package, Target)
  :- attr("node_target", Package, MyTarget),
     target_compatible(Target, MyTarget).
 
-% target_compatible(T1, T2) means code for T2 can run on T1
-% This order is dependent -> dependency in the node DAG, which
-% is contravariant with the target DAG.
-target_compatible(Target, Target) :- target(Target).
-target_compatible(Child, Parent) :- target_parent(Child, Parent).
-target_compatible(Descendent, Ancestor)
-  :- target_parent(Target, Ancestor),
-     target_compatible(Descendent, Target),
-     target(Target).
-
 #defined target_satisfies/2.
-#defined target_parent/2.
 
 % can't use targets on node if the compiler for the node doesn't support them
 error(2, "{0} compiler '{2}@{3}' incompatible with 'target={1}'", Package, Target, Compiler, Version)