Changes in src/ResolvExpr/TypeEnvironment.h [09c72d5:bd6e226]

File:

• src/ResolvExpr/TypeEnvironment.h (modified) (1 diff)

src/ResolvExpr/TypeEnvironment.h

@@ -37 +37 @@
         //
         // I've seen a TU go from 54 minutes to 1 minute 34 seconds with the addition of this comparator.
+        //
+        // Note: since this compares pointers for position, minor changes in the source file that affect
+        // memory layout can alter compilation time in unpredictable ways. For example, the placement
+        // of a line directive can reorder type pointers with respect to each other so that assertions
+        // are seen in different orders, causing a potentially different number of unification calls when
+        // resolving assertions. I've seen a TU go from 36 seconds to 27 seconds by reordering line directives
+        // alone, so it would be nice to fix this comparison so that assertions compare more consistently.
+        // I've tried to modify this to compare on mangle name instead of type as the second comparator, but
+        // this causes some assertions to never be recorded. More investigation is needed.
         struct AssertCompare {
                 bool operator()( DeclarationWithType * d1, DeclarationWithType * d2 ) const {