compiler.cfg.liveness: fix liveness computation in case where instruction uses a register it defines

basis/compiler/cfg/liveness/liveness-tests.factor

@@ -1,9 +1,14 @@
 USING: compiler.cfg.liveness compiler.cfg.debugger
 compiler.cfg.instructions compiler.cfg.predecessors
 compiler.cfg.registers compiler.cfg cpu.architecture
-accessors namespaces sequences kernel tools.test ;
+accessors namespaces sequences kernel tools.test vectors ;
 IN: compiler.cfg.liveness.tests
 
+: test-liveness ( -- )
+    cfg new 1 get >>entry
+    compute-predecessors
+    compute-live-sets ;
+
 ! Sanity check...
 
 V{
@@ -11,21 +16,22 @@ V{
     T{ ##replace f V int-regs 0 D 0 }
     T{ ##replace f V int-regs 1 D 1 }
     T{ ##peek f V int-regs 1 D 1 }
+    T{ ##branch }
 } 1 test-bb
 
 V{
     T{ ##replace f V int-regs 2 D 0 }
+    T{ ##branch }
 } 2 test-bb
 
 V{
     T{ ##replace f V int-regs 3 D 0 }
+    T{ ##return }
 } 3 test-bb
 
 1 get 2 get 3 get V{ } 2sequence >>successors drop
 
-cfg new 1 get >>entry
-compute-predecessors
-compute-live-sets
+test-liveness
 
 [
     H{
@@ -35,4 +41,22 @@ compute-live-sets
     }
 ]
 [ 1 get live-in ]
-unit-test
+unit-test
+
+! Tricky case; defs must be killed before uses
+
+V{
+    T{ ##peek f V int-regs 0 D 0 }
+    T{ ##branch }
+} 1 test-bb
+
+V{
+    T{ ##add-imm f V int-regs 0 V int-regs 0 10 }
+    T{ ##return }
+} 2 test-bb
+
+1 get 2 get 1vector >>successors drop
+
+test-liveness
+
+[ H{ { V int-regs 0 V int-regs 0 } } ] [ 2 get live-in ] unit-test

basis/compiler/cfg/liveness/liveness.factor

@@ -12,11 +12,14 @@ BACKWARD-ANALYSIS: live
 
 GENERIC: insn-liveness ( live-set insn -- )
 
+: kill-defs ( live-set insn -- live-set )
+    defs-vregs [ over delete-at ] each ;
+
+: gen-uses ( live-set insn -- live-set )
+    dup ##phi? [ drop ] [ uses-vregs [ over conjoin ] each ] if ;
+
 : transfer-liveness ( live-set instructions -- live-set' )
-    [ clone ] [ <reversed> ] bi* [
-        [ dup ##phi? [ drop ] [ uses-vregs [ over conjoin ] each ] if ]
-        [ defs-vregs [ over delete-at ] each ] bi
-    ] each ;
+    [ clone ] [ <reversed> ] bi* [ [ kill-defs ] [ gen-uses ] bi ] each ;
 
 : local-live-in ( instructions -- live-set )
     [ H{ } ] dip transfer-liveness keys ;