compiler.cfg.ssa.destruction: try and sort the vreg pairs before

elimination, this way you always get the same leader info

basis/compiler/cfg/ssa/destruction/destruction-docs.factor

@@ -1,6 +1,6 @@
 USING: compiler.cfg compiler.cfg.instructions
 compiler.cfg.ssa.destruction.private compiler.cfg.ssa.interference help.markup
-help.syntax kernel ;
+help.syntax kernel sequences ;
 IN: compiler.cfg.ssa.destruction
 
 HELP: class-element-map
@@ -25,7 +25,12 @@ HELP: copies
 HELP: try-eliminate-copy
 { $values { "follower" "vreg" } { "leader" "vreg" } { "must?" boolean } }
 { $description "Tries to eliminate a vreg copy from 'leader' to 'follower'. If 'must?' is " { $link t } " then a " { $link vregs-shouldn't-interfere } " error is thrown if the vregs interfere." }
-{ $see-also vregs-interfere? } ;
+{ $see-also try-eliminate-copies vregs-interfere? } ;
+
+HELP: try-eliminate-copies
+{ $values { "pairs" "a sequence of vreg pairs" } { "must?" boolean } }
+{ $description "Tries to eliminate the vreg copies in the " { $link sequence } " 'pairs'. If 'must?' is " { $link t } " then a " { $link vregs-shouldn't-interfere } " error is thrown if any of the vregs interfere. To ensure deterministic " { $link leader-map } " data, the pairs are sorted." }
+{ $see-also try-eliminate-copy } ;
 
 ARTICLE: "compiler.cfg.ssa.destruction" "SSA Destruction"
 "Because of the design of the register allocator, this pass has three peculiar properties."
@@ -33,6 +38,9 @@ ARTICLE: "compiler.cfg.ssa.destruction" "SSA Destruction"
   "Instead of renaming vreg usages in the CFG, a map from vregs to canonical representatives is computed. This allows the register allocator to use the original SSA names to get reaching definitions."
   { "Useless " { $link ##copy } " instructions, and all " { $link ##phi } " instructions, are eliminated, so the register allocator does not have to remove any redundant operations." }
   { "This pass computes live sets and fills out the " { $slot "gc-roots" } " slots of GC maps with " { $vocab-link "compiler.cfg.liveness" } ", so the linear scan register allocator does not need to compute liveness again." }
-} ;
+}
+$nl
+"Main entry point:"
+{ $subsections destruct-ssa } ;
 
 ABOUT: "compiler.cfg.ssa.destruction"

basis/compiler/cfg/ssa/destruction/destruction-tests.factor

@@ -1,8 +1,10 @@
-USING: alien.syntax compiler.cfg.def-use compiler.cfg.instructions
-compiler.cfg.registers compiler.cfg.ssa.destruction
-compiler.cfg.ssa.destruction.leaders
+USING: alien.syntax assocs compiler.cfg.def-use
+compiler.cfg.instructions compiler.cfg.registers
+compiler.cfg.ssa.destruction compiler.cfg.ssa.destruction.leaders
 compiler.cfg.ssa.destruction.private compiler.cfg.utilities
-cpu.architecture cpu.x86.assembler.operands kernel make namespaces tools.test ;
+cpu.architecture cpu.x86.assembler.operands grouping kernel make namespaces
+random sequences tools.test ;
+QUALIFIED: sets
 IN: compiler.cfg.ssa.destruction.tests
 
 ! cleanup-insn
@@ -63,9 +65,9 @@ IN: compiler.cfg.ssa.destruction.tests
     } 0 insns>block block>cfg destruct-ssa
 ] unit-test
 
-! must-eliminate-copy
+! try-eliminate-copy
 { } [
-    10 10 must-eliminate-copy
+    10 10 f try-eliminate-copy
 ] unit-test
 
 ! prepare-insn
@@ -80,3 +82,20 @@ IN: compiler.cfg.ssa.destruction.tests
     T{ ##parallel-copy { values V{ { 3 4 } { 7 8 } } } } prepare-insn
     copies get
 ] unit-test
+
+! All this work to make the 'values' order non-deterministic.
+: make-phi-inputs ( -- assoc )
+    H{ } clone [
+        { 2287 2288 } [
+            10 iota 1 sample first rot set-at
+        ] with each
+    ] keep ;
+
+{ t } [
+    10 [
+        { 2286 2287 2288 } sets:unique leader-map set
+        2286 make-phi-inputs ##phi new-insn
+        prepare-insn
+        2286 leader
+    ] replicate all-equal?
+] unit-test

basis/compiler/cfg/ssa/destruction/destruction.factor

@@ -7,7 +7,7 @@ compiler.cfg.registers compiler.cfg.rpo compiler.cfg.ssa.cssa
 compiler.cfg.ssa.destruction.leaders
 compiler.cfg.ssa.interference
 compiler.cfg.ssa.interference.live-ranges compiler.cfg.utilities
-cpu.architecture kernel make namespaces sequences sets ;
+cpu.architecture fry kernel make namespaces sequences sets sorting ;
 FROM: namespaces => set ;
 IN: compiler.cfg.ssa.destruction
 
@@ -73,17 +73,23 @@ ERROR: vregs-shouldn't-interfere vreg1 vreg2 ;
         ] [ -rot coalesce-vregs drop ] if
     ] if ;
 
+: try-eliminate-copies ( pairs must? -- )
+    [ natural-sort ] dip '[ first2 _ try-eliminate-copy ] each ;
+
 M: ##tagged>integer prepare-insn
     [ dst>> ] [ src>> ] bi t try-eliminate-copy ;
 
+: zip-scalar ( scalar seq -- pairs )
+    [ 2array ] with map ;
+
 M: ##phi prepare-insn
-    [ dst>> ] [ inputs>> values ] bi [ t try-eliminate-copy ] with each ;
+    [ dst>> ] [ inputs>> values ] bi zip-scalar t try-eliminate-copies ;
 
 : prepare-coalescing ( cfg -- )
     init-coalescing [ [ prepare-insn ] each ] simple-analysis ;
 
 : process-copies ( copies -- )
-    [ f try-eliminate-copy ] assoc-each ;
+    >alist f try-eliminate-copies ;
 
 : perform-coalescing ( cfg -- )
     prepare-coalescing copies get process-copies ;