File 6401-beam_ssa-Optimize-dominator-calculation-again.patch of Package erlang

From 3ff39a6702b62764c92ac158b8c471390559e8f0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Mon, 7 Feb 2022 11:51:13 +0100
Subject: [PATCH] beam_ssa: Optimize dominator calculation (again)

For the example in #5686, the time for running the `place_frames`
sub pass of `beam_ssa_pre_codegen` is reduced from about 30 seconds
to less than 20 seconds on my computer, and the time for each of
the `beam_ssa_bool` and `ssa_opt_sink` passes is almost halved.
---
 lib/compiler/src/beam_ssa.erl | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/lib/compiler/src/beam_ssa.erl b/lib/compiler/src/beam_ssa.erl
index 85da3b5937..2bb0870c27 100644
--- a/lib/compiler/src/beam_ssa.erl
+++ b/lib/compiler/src/beam_ssa.erl
@@ -798,9 +798,23 @@ dom_intersection_1([E1|Es1]=Set1, [E2|Es2]=Set2, Df) ->
     #{E1:=Df1,E2:=Df2} = Df,
     if
         Df1 > Df2 ->
-            dom_intersection_1(Es1, Set2, Df);
+            dom_intersection_2(Es1, Set2, Df, Df2);
         Df2 > Df1 ->
-            dom_intersection_1(Es2, Set1, Df);  %switch arguments
+            dom_intersection_2(Es2, Set1, Df, Df1);
+        true ->                                  %Set1 == Set2
+            %% The common suffix of the sets is the intersection.
+            Set1
+    end.
+
+dom_intersection_2([E1|Es1]=Set1, [_|Es2]=Set2, Df, Df2) ->
+    %% Blocks are numbered in the order they are found in
+    %% reverse postorder.
+    #{E1:=Df1} = Df,
+    if
+        Df1 > Df2 ->
+            dom_intersection_2(Es1, Set2, Df, Df2);
+        Df2 > Df1 ->
+            dom_intersection_2(Es2, Set1, Df, Df1);  %switch arguments
         true ->                                  %Set1 == Set2
             %% The common suffix of the sets is the intersection.
             Set1
-- 
2.34.1