cranelift: Optimize select+icmp into {s,u}{min,max}

cranelift/codegen/src/opts/algebraic.isle

@@ -345,3 +345,131 @@
              (uextend $I64 x @ (value_type $I32))
              (iconst _ (u64_from_imm64 0))))
       (iconst ty (imm64 1)))
+
+
+;; Transform select-of-icmp into {u,s}{min,max} instructions where possible.
+(rule (simplify
+       (select ty (icmp _ (IntCC.SignedGreaterThan) x y) x y))
+      (smax ty x y))
+(rule (simplify
+       (select ty (icmp _ (IntCC.SignedGreaterThanOrEqual) x y) x y))
+      (smax ty x y))
+(rule (simplify
+       (select ty (icmp _ (IntCC.UnsignedGreaterThan) x y) x y))
+      (umax ty x y))
+(rule (simplify
+       (select ty (icmp _ (IntCC.UnsignedGreaterThanOrEqual) x y) x y))
+      (umax ty x y))
+(rule (simplify
+       (select ty (icmp _ (IntCC.SignedLessThan) x y) x y))
+      (smin ty x y))
+(rule (simplify
+       (select ty (icmp _ (IntCC.SignedLessThanOrEqual) x y) x y))
+      (smin ty x y))
+(rule (simplify
+       (select ty (icmp _ (IntCC.UnsignedLessThan) x y) x y))
+      (umin ty x y))
+(rule (simplify
+       (select 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
+       (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))
+      (smax ty x y))
+(rule (simplify
+       (vselect ty (icmp _ (IntCC.SignedGreaterThanOrEqual) x y) x y))
+      (smax ty x y))
+(rule (simplify
+       (vselect ty (icmp _ (IntCC.UnsignedGreaterThan) x y) x y))
+      (umax ty x y))
+(rule (simplify
+       (vselect ty (icmp _ (IntCC.UnsignedGreaterThanOrEqual) x y) x y))
+      (umax ty x y))
+(rule (simplify
+       (vselect ty (icmp _ (IntCC.SignedLessThan) x y) x y))
+      (smin ty x y))
+(rule (simplify
+       (vselect ty (icmp _ (IntCC.SignedLessThanOrEqual) x y) x y))
+      (smin ty x y))
+(rule (simplify
+       (vselect ty (icmp _ (IntCC.UnsignedLessThan) x y) x y))
+      (umin ty x y))
+(rule (simplify
+       (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
+;;
+;; fmax_pseudo docs state:
+;; The behaviour for this operations is defined as  fmax_pseudo(a, b) = (a < b) ? b : a, and the behaviour for zero
+;; or NaN inputs follows from the behaviour of < with such inputs.
+;;
+;; That is exactly the operation that we match here!
+(rule (simplify
+       (select ty (fcmp _ (FloatCC.LessThan) x y) x y))
+      (fmin_pseudo ty x y))
+(rule (simplify
+       (select ty (fcmp _ (FloatCC.GreaterThan) x y) x y))
+      (fmax_pseudo ty x y))
+
+;; Do the same for vectors
+(rule (simplify
+       (vselect ty (fcmp _ (FloatCC.LessThan) x y) x y))
+      (fmin_pseudo ty x y))
+(rule (simplify
+       (vselect ty (fcmp _ (FloatCC.GreaterThan) x y) x y))
+      (fmax_pseudo ty x y))

cranelift/filetests/filetests/egraph/licm.clif

@@ -31,8 +31,8 @@ block2(v9: i32):
 ; check:      v8 = iadd v2, v3
 ; check:      brif v6, block2, block1(v8)
 
+
 ; check:  block2:
 ; check:      v10 = iconst.i32 1
 ; check:      v4 = iadd.i32 v1, v10
 ; check:      return v4
-

cranelift/filetests/filetests/egraph/select.clif

@@ -0,0 +1,155 @@
+test optimize
+set opt_level=speed
+set use_egraphs=true
+target x86_64
+target aarch64
+target s390x
+target riscv64
+
+function %select_sgt_to_smax(i32, i32) -> i32 {
+block0(v0: i32, v1: i32):
+    v2 = icmp sgt v0, v1
+    v3 = select v2, v0, v1
+    return v3
+}
+
+; check: block0(v0: i32, v1: i32):
+; check:    v4 = smax v0, v1
+; 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
+    v3 = select v2, v0, v1
+    return v3
+}
+
+; check: block0(v0: i32, v1: i32):
+; check:    v4 = smax v0, v1
+; check:    return v4
+
+
+function %select_ugt_to_umax(i32, i32) -> i32 {
+block0(v0: i32, v1: i32):
+    v2 = icmp ugt v0, v1
+    v3 = select v2, v0, v1
+    return v3
+}
+
+; check: block0(v0: i32, v1: i32):
+; check:    v4 = umax v0, v1
+; check:    return v4
+
+
+function %select_uge_to_umax(i32, i32) -> i32 {
+block0(v0: i32, v1: i32):
+    v2 = icmp uge v0, v1
+    v3 = select v2, v0, v1
+    return v3
+}
+
+; check: block0(v0: i32, v1: i32):
+; check:    v4 = umax v0, v1
+; check:    return v4
+
+
+
+function %select_slt_to_smin(i32, i32) -> i32 {
+block0(v0: i32, v1: i32):
+    v2 = icmp slt v0, v1
+    v3 = select v2, v0, v1
+    return v3
+}
+
+; check: block0(v0: i32, v1: i32):
+; check:    v4 = smin v0, v1
+; check:    return v4
+
+
+function %select_sle_to_smin(i32, i32) -> i32 {
+block0(v0: i32, v1: i32):
+    v2 = icmp sle v0, v1
+    v3 = select v2, v0, v1
+    return v3
+}
+
+; check: block0(v0: i32, v1: i32):
+; check:    v4 = smin v0, v1
+; check:    return v4
+
+
+function %select_ult_to_umin(i32, i32) -> i32 {
+block0(v0: i32, v1: i32):
+    v2 = icmp ult v0, v1
+    v3 = select v2, v0, v1
+    return v3
+}
+
+; check: block0(v0: i32, v1: i32):
+; check:    v4 = umin v0, v1
+; check:    return v4
+
+
+function %select_ule_to_umin(i32, i32) -> i32 {
+block0(v0: i32, v1: i32):
+    v2 = icmp ule v0, v1
+    v3 = select v2, v0, v1
+    return v3
+}
+
+; check: block0(v0: i32, v1: i32):
+; check:    v4 = umin v0, v1
+; check:    return v4
+
+
+
+function %select_with_different_regs_does_not_optimize(i32, i32, i32, i32) -> i32 {
+block0(v0: i32, v1: i32, v2: i32, v3: i32):
+    v4 = icmp ule v0, v1
+    v5 = select v4, v2, v3
+    return v5
+}
+
+; check: block0(v0: i32, v1: i32, v2: i32, v3: i32):
+; check:    v4 = icmp ule v0, v1
+; check:    v5 = select v4, v2, v3
+; check:    return v5
+
+
+
+
+function %select_fcmp_gt_to_fmax_pseudo(f32, f32) -> f32 {
+block0(v0: f32, v1: f32):
+    v2 = fcmp gt v0, v1
+    v3 = select v2, v0, v1
+    return v3
+}
+
+; check: block0(v0: f32, v1: f32):
+; check:    v4 = fmax_pseudo v0, v1
+; check:    return v4
+
+function %select_fcmp_lt_to_fmin_pseudo(f32, f32) -> f32 {
+block0(v0: f32, v1: f32):
+    v2 = fcmp lt v0, v1
+    v3 = select v2, v0, v1
+    return v3
+}
+
+; check: block0(v0: f32, v1: f32):
+; check:    v4 = fmin_pseudo v0, v1
+; check:    return v4