beam_type: Use the complete register map when calculating liveness

When calculating the number of live registers for allocation
instruction, it is not always safe to start with the number of live
registers at the start of the block. We will need to use the register
map to know whether there are any holes (dead registers) that are not
subsequently filled.

If the allocation instruction already has a number of live registers
calculated, there is nothing to be gained by raising it.

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/compiler/test/guard_SUITE.erl b/lib/compiler/test/guard_SUITE.erl
index 8db47ffa40..08279d9408 100644
--- a/lib/compiler/test/guard_SUITE.erl
+++ b/lib/compiler/test/guard_SUITE.erl
@@ -1802,6 +1802,12 @@ bad_guards(Config) when is_list(Config) ->
     fc(catch bad_guards_2(#{a=>0,b=>0}, [x])),
     fc(catch bad_guards_2(not_a_map, [x])),
     fc(catch bad_guards_2(42, [x])),
+
+    fc(catch bad_guards_3(#{a=>0,b=>0}, [])),
+    fc(catch bad_guards_3(#{a=>0,b=>0}, [x])),
+    fc(catch bad_guards_3(not_a_map, [x])),
+    fc(catch bad_guards_3(42, [x])),
+
     ok.
 
 %% beam_bool used to produce GC BIF instructions whose
@@ -1813,6 +1819,12 @@ bad_guards_1(X, [_]) when {{X}}, -X ->
 bad_guards_2(M, [_]) when M#{a := 0, b => 0}, map_size(M) ->
     ok.
 
+%% beam_type used to produce an GC BIF instruction whose Live operand
+%% included uninitialized registers.
+
+bad_guards_3(M, [_]) when is_map(M) andalso M#{a := 0, b => 0}, length(M) ->
+    ok.
+
 %% Call this function to turn off constant propagation.
 id(I) -> I.