cranelift: simplify icmp against UMAX/SMIN/SMAX (#6037)

* cranelift: simplify `icmp` against UMAX/SMIN/SMAX

* Add tests for icmp against numeric limits

cranelift/codegen/src/isle_prelude.rs

@@ -217,6 +217,36 @@ macro_rules! isle_common_prelude_methods {
             u64::MAX >> shift
         }
 
+        #[inline]
+        fn ty_umin(&mut self, _ty: Type) -> u64 {
+            0
+        }
+
+        #[inline]
+        fn ty_umax(&mut self, ty: Type) -> u64 {
+            self.ty_mask(ty)
+        }
+
+        #[inline]
+        fn ty_smin(&mut self, ty: Type) -> u64 {
+            let ty_bits = ty.bits();
+            debug_assert_ne!(ty_bits, 0);
+            let shift = 64_u64
+                .checked_sub(ty_bits.into())
+                .expect("unimplemented for > 64 bits");
+            (i64::MIN as u64) >> shift
+        }
+
+        #[inline]
+        fn ty_smax(&mut self, ty: Type) -> u64 {
+            let ty_bits = ty.bits();
+            debug_assert_ne!(ty_bits, 0);
+            let shift = 64_u64
+                .checked_sub(ty_bits.into())
+                .expect("unimplemented for > 64 bits");
+            (i64::MAX as u64) >> shift
+        }
+
         fn fits_in_16(&mut self, ty: Type) -> Option<Type> {
             if ty.bits() <= 16 && !ty.is_dynamic_vector() {
                 Some(ty)

cranelift/codegen/src/opts/algebraic.isle

@@ -377,20 +377,97 @@
              (iconst _ (u64_from_imm64 1))))
       extend)
 
-;; `x < 0` is always false for unsigned integers, and `x >= 0` is always true
-;; for unsigned integers, along with their reversals.
+;; ult(x, 0) == false.
 (rule (simplify
-       (icmp (fits_in_64 (ty_int ty))
-             (IntCC.UnsignedLessThan)
-             _
-             (iconst _ (u64_from_imm64 0))))
-      (iconst ty (imm64 0)))
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.UnsignedLessThan) x zero @ (iconst _ (u64_from_imm64 0))))
+      (subsume (iconst bty (imm64 0))))
+
+;; ule(x, 0) == eq(x, 0)
 (rule (simplify
-       (icmp (fits_in_64 (ty_int ty))
-             (IntCC.UnsignedGreaterThanOrEqual)
-             _
-             (iconst _ (u64_from_imm64 0))))
-      (iconst ty (imm64 1)))
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.UnsignedLessThanOrEqual) x zero @ (iconst _ (u64_from_imm64 0))))
+      (icmp bty (IntCC.Equal) x zero))
+
+;; ugt(x, 0) == ne(x, 0).
+(rule (simplify
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.UnsignedGreaterThan) x zero @ (iconst _ (u64_from_imm64 0))))
+      (icmp bty (IntCC.NotEqual) x zero))
+
+;; uge(x, 0) == true.
+(rule (simplify
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.UnsignedGreaterThanOrEqual) x zero @ (iconst _ (u64_from_imm64 0))))
+      (subsume (iconst bty (imm64 1))))
+
+;; ult(x, UMAX) == ne(x, UMAX).
+(rule (simplify
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.UnsignedLessThan) x umax @ (iconst cty (u64_from_imm64 y))))
+       (if-let $true (u64_eq y (ty_umax cty)))
+       (icmp bty (IntCC.NotEqual) x umax))
+
+;; ule(x, UMAX) == true.
+(rule (simplify
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.UnsignedLessThanOrEqual) x umax @ (iconst cty (u64_from_imm64 y))))
+       (if-let $true (u64_eq y (ty_umax cty)))
+       (subsume (iconst bty (imm64 1))))
+
+;; ugt(x, UMAX) == false.
+(rule (simplify
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.UnsignedGreaterThan) x umax @ (iconst cty (u64_from_imm64 y))))
+       (if-let $true (u64_eq y (ty_umax cty)))
+       (subsume (iconst bty (imm64 0))))
+
+;; uge(x, UMAX) == eq(x, UMAX).
+(rule (simplify
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.UnsignedGreaterThanOrEqual) x umax @ (iconst cty (u64_from_imm64 y))))
+       (if-let $true (u64_eq y (ty_umax cty)))
+       (icmp bty (IntCC.Equal) x umax))
+
+;; slt(x, SMIN) == false.
+(rule (simplify
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.SignedLessThan) x smin @ (iconst cty (u64_from_imm64 y))))
+       (if-let $true (u64_eq y (ty_smin cty)))
+       (subsume (iconst bty (imm64 0))))
+
+;; sle(x, SMIN) == eq(x, SMIN).
+(rule (simplify
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.SignedLessThanOrEqual) x smin @ (iconst cty (u64_from_imm64 y))))
+       (if-let $true (u64_eq y (ty_smin cty)))
+       (icmp bty (IntCC.Equal) x smin))
+
+;; sgt(x, SMIN) == ne(x, SMIN).
+(rule (simplify
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.SignedGreaterThan) x smin @ (iconst cty (u64_from_imm64 y))))
+       (if-let $true (u64_eq y (ty_smin cty)))
+       (icmp bty (IntCC.NotEqual) x smin))
+
+;; sge(x, SMIN) == true.
+(rule (simplify
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.SignedGreaterThanOrEqual) x smin @ (iconst cty (u64_from_imm64 y))))
+       (if-let $true (u64_eq y (ty_smin cty)))
+       (subsume (iconst bty (imm64 1))))
+
+;; slt(x, SMAX) == ne(x, SMAX).
+(rule (simplify
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.SignedLessThan) x smax @ (iconst cty (u64_from_imm64 y))))
+       (if-let $true (u64_eq y (ty_smax cty)))
+       (icmp bty (IntCC.NotEqual) x smax))
+
+;; sle(x, SMAX) == true.
+(rule (simplify
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.SignedLessThanOrEqual) x smax @ (iconst cty (u64_from_imm64 y))))
+       (if-let $true (u64_eq y (ty_smax cty)))
+       (subsume (iconst bty (imm64 1))))
+
+;; sgt(x, SMAX) == false.
+(rule (simplify
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.SignedGreaterThan) x smax @ (iconst cty (u64_from_imm64 y))))
+       (if-let $true (u64_eq y (ty_smax cty)))
+       (subsume (iconst bty (imm64 0))))
+
+;; sge(x, SMAX) == eq(x, SMAX).
+(rule (simplify
+       (icmp (fits_in_64 (ty_int bty)) (IntCC.SignedGreaterThanOrEqual) x smax @ (iconst cty (u64_from_imm64 y))))
+       (if-let $true (u64_eq y (ty_smax cty)))
+       (icmp bty (IntCC.Equal) x smax))
 
 ;; 32-bit integers zero-extended to 64-bit integers are never negative
 (rule (simplify

cranelift/codegen/src/prelude.isle

@@ -208,6 +208,23 @@
 
 (extern const $I32X4XN Type)
 
+;; Get the unsigned minimum value for a given type.
+;; This always zero, but is included for completeness.
+(decl pure ty_umin (Type) u64)
+(extern constructor ty_umin ty_umin)
+
+;; Get the unsigned maximum value for a given type.
+(decl pure ty_umax (Type) u64)
+(extern constructor ty_umax ty_umax)
+
+;; Get the signed minimum value for a given type.
+(decl pure ty_smin (Type) u64)
+(extern constructor ty_smin ty_smin)
+
+;; Get the signed maximum value for a given type.
+(decl pure ty_smax (Type) u64)
+(extern constructor ty_smax ty_smax)
+
 ;; Get the bit width of a given type.
 (decl pure ty_bits (Type) u8)
 (extern constructor ty_bits ty_bits)

cranelift/filetests/filetests/egraph/algebraic.clif

@@ -418,45 +418,149 @@ block0(v1: i64, v2: i64):
 ; check: v4 = uextend.i64 v3
 ; check: return v4
 
-function %ult_zero_always_false(i64) -> i8 {
-block0(v1: i64):
-    v2 = iconst.i64 0
-    v3 = icmp ult v1, v2
-    return v3
+function %icmp_ult_0(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0
+    v2 = icmp ult v0, v1
+    return v2
+    ; check: v3 = iconst.i8 0
+    ; check: return v3
 }
 
-; check: v4 = iconst.i8 0
-; check: return v4
-
-function %ugt_zero_always_false(i64) -> i8 {
-block0(v1: i64):
-    v2 = iconst.i64 0
-    v3 = icmp ugt v2, v1
-    return v3
+function %icmp_ule_0(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0
+    v2 = icmp ule v0, v1
+    return v2
+    ; check: v3 = icmp eq v0, v1
+    ; check: return v3
 }
 
-; check: v5 = iconst.i8 0
-; check: return v5
-
-function %uge_zero_always_false(i64) -> i8 {
-block0(v1: i64):
-    v2 = iconst.i64 0
-    v3 = icmp uge v1, v2
-    return v3
+function %icmp_ugt_0(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0
+    v2 = icmp ugt v0, v1
+    return v2
+    ; check: v3 = icmp ne v0, v1
+    ; check: return v3
 }
 
-; check: v4 = iconst.i8 1
-; check: return v4
-
-function %ule_zero_always_false(i64) -> i8 {
-block0(v1: i64):
-    v2 = iconst.i64 0
-    v3 = icmp ule v2, v1
-    return v3
+function %icmp_uge_0(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0
+    v2 = icmp uge v0, v1
+    return v2
+    ; check: v3 = iconst.i8 1
+    ; check: return v3
 }
 
-; check: v5 = iconst.i8 1
-; check: return v5
+function %icmp_ult_umax(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0xffff_ffff
+    v2 = icmp ult v0, v1
+    return v2
+    ; check: v3 = icmp ne v0, v1
+    ; check: return v3
+}
+
+function %icmp_ule_umax(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0xffff_ffff
+    v2 = icmp ule v0, v1
+    return v2
+    ; check: v3 = iconst.i8 1
+    ; check: return v3
+}
+
+function %icmp_ugt_umax(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0xffff_ffff
+    v2 = icmp ugt v0, v1
+    return v2
+    ; check: v3 = iconst.i8 0
+    ; check: return v3
+}
+
+function %icmp_uge_umax(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0xffff_ffff
+    v2 = icmp uge v0, v1
+    return v2
+    ; check: v3 = icmp eq v0, v1
+    ; check: return v3
+}
+
+function %icmp_slt_smin(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0x8000_0000
+    v2 = icmp slt v0, v1
+    return v2
+    ; check: v3 = iconst.i8 0
+    ; check: return v3
+}
+
+function %icmp_sle_smin(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0x8000_0000
+    v2 = icmp sle v0, v1
+    return v2
+    ; check: v3 = icmp eq v0, v1
+    ; check: return v3
+}
+
+function %icmp_sgt_smin(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0x8000_0000
+    v2 = icmp sgt v0, v1
+    return v2
+    ; check: v3 = icmp ne v0, v1
+    ; check: return v3
+}
+
+function %icmp_sge_smin(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0x8000_0000
+    v2 = icmp sge v0, v1
+    return v2
+    ; check: v3 = iconst.i8 1
+    ; check: return v3
+}
+
+function %icmp_slt_smax(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0x7FFF_FFFF
+    v2 = icmp slt v0, v1
+    return v2
+    ; check: v3 = icmp ne v0, v1
+    ; check: return v3
+}
+
+function %icmp_sle_smax(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0x7FFF_FFFF
+    v2 = icmp sle v0, v1
+    return v2
+    ; check: v3 = iconst.i8 1
+    ; check: return v3
+}
+
+function %icmp_sgt_smax(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0x7FFF_FFFF
+    v2 = icmp sgt v0, v1
+    return v2
+    ; check: v3 = iconst.i8 0
+    ; check: return v3
+}
+
+function %icmp_sge_smax(i32) -> i8 {
+block0(v0: i32):
+    v1 = iconst.i32 0x7FFF_FFFF
+    v2 = icmp sge v0, v1
+    return v2
+    ; check: v3 = icmp eq v0, v1
+    ; check: return v3
+}
 
 function %extend_always_above_zero(i32) -> i8 {
 block0(v1: i32):