cranelift: Add inverted forms of min/max rules

Author: afonso360

cranelift/codegen/src/opts/algebraic.isle

@@ -374,6 +374,32 @@
       (umin ty x y))
 
 
+;; These are the same rules as above, but when the operands for select are swapped
+(rule (simplify
+       (select ty (icmp _ (IntCC.SignedLessThan) x y) y x))
+      (smax ty x y))
+(rule (simplify
+       (select ty (icmp _ (IntCC.SignedLessThanOrEqual) x y) y x))
+      (smax ty x y))
+(rule (simplify
+       (select ty (icmp _ (IntCC.UnsignedLessThan) x y) y x))
+      (umax ty x y))
+(rule (simplify
+       (select ty (icmp _ (IntCC.UnsignedLessThanOrEqual) x y) y x))
+      (umax ty x y))
+(rule (simplify
+       (select ty (icmp _ (IntCC.SignedGreaterThan) x y) y x))
+      (smin ty x y))
+(rule (simplify
+       (select ty (icmp _ (IntCC.SignedGreaterThanOrEqual) x y) y x))
+      (smin ty x y))
+(rule (simplify
+       (select ty (icmp _ (IntCC.UnsignedGreaterThan) x y) y x))
+      (umin ty x y))
+(rule (simplify
+       (select ty (icmp _ (IntCC.UnsignedGreaterThanOrEqual) x y) y x))
+      (umin ty x y))
+
 ;; Transform vselect-of-icmp into {u,s}{min,max} instructions where possible.
 (rule (simplify
        (vselect ty (icmp _ (IntCC.SignedGreaterThan) x y) x y))
@@ -400,7 +426,31 @@
        (vselect ty (icmp _ (IntCC.UnsignedLessThanOrEqual) x y) x y))
       (umin ty x y))
 
-
+;; These are the same rules as above, but when the operands for select are swapped
+(rule (simplify
+       (vselect ty (icmp _ (IntCC.SignedLessThan) x y) y x))
+      (smax ty x y))
+(rule (simplify
+       (vselect ty (icmp _ (IntCC.SignedLessThanOrEqual) x y) y x))
+      (smax ty x y))
+(rule (simplify
+       (vselect ty (icmp _ (IntCC.UnsignedLessThan) x y) y x))
+      (umax ty x y))
+(rule (simplify
+       (vselect ty (icmp _ (IntCC.UnsignedLessThanOrEqual) x y) y x))
+      (umax ty x y))
+(rule (simplify
+       (vselect ty (icmp _ (IntCC.SignedGreaterThan) x y) y x))
+      (smin ty x y))
+(rule (simplify
+       (vselect ty (icmp _ (IntCC.SignedGreaterThanOrEqual) x y) y x))
+      (smin ty x y))
+(rule (simplify
+       (vselect ty (icmp _ (IntCC.UnsignedGreaterThan) x y) y x))
+      (umin ty x y))
+(rule (simplify
+       (vselect ty (icmp _ (IntCC.UnsignedGreaterThanOrEqual) x y) y x))
+      (umin ty x y))
 
 ;; For floats convert fcmp lt into pseudo_min and gt into pseudo_max
 ;;

cranelift/filetests/filetests/egraph/select.clif

@@ -18,6 +18,19 @@ block0(v0: i32, v1: i32):
 ; check:    return v4
 
 
+; This tests an inverted select, where the operands are swapped.
+function %select_sgt_to_smax_inverse(i32, i32) -> i32 {
+block0(v0: i32, v1: i32):
+    v2 = icmp sgt v0, v1
+    v3 = select v2, v1, v0
+    return v3
+}
+
+; check: block0(v0: i32, v1: i32):
+; check:    v4 = smin v0, v1
+; check:    return v4
+
+
 function %select_sge_to_smax(i32, i32) -> i32 {
 block0(v0: i32, v1: i32):
     v2 = icmp sge v0, v1

cranelift/filetests/filetests/egraph/vselect.clif

@@ -17,6 +17,20 @@ block0(v0: i32x4, v1: i32x4):
 ; check:    return v4
 
 
+; This tests an inverted vselect, where the operands are swapped.
+function %vselect_sgt_to_smax(i32x4, i32x4) -> i32x4 {
+block0(v0: i32x4, v1: i32x4):
+    v2 = icmp sgt v0, v1
+    v3 = vselect v2, v1, v0
+    return v3
+}
+
+; check: block0(v0: i32x4, v1: i32x4):
+; check:    v4 = smin v0, v1
+; check:    return v4
+
+
+
 function %vselect_sge_to_smax(i32x4, i32x4) -> i32x4 {
 block0(v0: i32x4, v1: i32x4):
     v2 = icmp sge v0, v1