Constant-fold some expressions involving variables.

zeek · May 10, 2023 · 0df13a5 · 0df13a5
1 parent b26c4a9
commit 0df13a5
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Showing 2 changed files with 26 additions and 2 deletions.
diff --git a/hilti/toolchain/src/compiler/optimizer.cc b/hilti/toolchain/src/compiler/optimizer.cc
@@ -852,6 +852,18 @@ struct ConstantFoldingVisitor : OptimizerVisitor, visitor::PreOrder<bool, Consta
                     replaceNode(p, builder::bool_(true));
                     return true;
                 }
+
+                // If the LHS is some variable and the RHS is a literal `true`
+                // the result is always `true` and we can replace the AND without
+                // removing side-effects.
+                if ( auto lhs = x.op0().tryAs<expression::ResolvedID>();
+                     lhs &&
+                     (lhs->declaration().isA<declaration::GlobalVariable>() ||
+                      lhs->declaration().isA<declaration::LocalVariable>()) &&
+                     rhs && rhs.value() ) {
+                    replaceNode(p, builder::bool_(true));
+                    return true;
+                }
             }
         };
 
@@ -877,6 +889,18 @@ struct ConstantFoldingVisitor : OptimizerVisitor, visitor::PreOrder<bool, Consta
                     replaceNode(p, builder::bool_(false));
                     return true;
                 }
+
+                // If the LHS is some variable and the RHS is a literal `false`
+                // the result is always `false` and we can replace the AND without
+                // removing side-effects.
+                if ( auto lhs = x.op0().tryAs<expression::ResolvedID>();
+                     lhs &&
+                     (lhs->declaration().isA<declaration::GlobalVariable>() ||
+                      lhs->declaration().isA<declaration::LocalVariable>()) &&
+                     rhs && ! rhs.value() ) {
+                    replaceNode(p, builder::bool_(false));
+                    return true;
+                }
             }
         };
 

diff --git a/tests/Baseline/hilti.optimization.const/opt.hlt b/tests/Baseline/hilti.optimization.const/opt.hlt
@@ -31,10 +31,10 @@ False;
 True;
 1;
 1;
-a || True;
+True;
 a || False;
 a && True;
-a && False;
+False;
 True;
 False || a;
 True && a;