Constant propagation opts

cranelift/codegen/src/isle_prelude.rs

@@ -27,12 +27,38 @@ macro_rules! isle_common_prelude_methods {
             self.checked_add_with_type(ty, a, b).is_none()
         }
 
+        #[inline]
+        fn imm64_clz(&mut self, ty: Type, a: Imm64) -> Imm64 {
+            let bits = ty.bits();
+            assert!(bits <= 64);
+            let clz_offset = 64 - bits;
+            let a_v: u64 = a.bits().cast_unsigned();
+            let lz = a_v.leading_zeros() - clz_offset;
+            Imm64::new(i64::from(lz))
+        }
+
+        #[inline]
+        fn imm64_ctz(&mut self, ty: Type, a: Imm64) -> Imm64 {
+            let bits = ty.bits();
+            assert!(bits <= 64);
+            let a_v: u64 = a.bits().cast_unsigned();
+            if a_v == 0 {
+                // ctz(0) is defined to be the number of bits in the type.
+                Imm64::new(i64::from(bits))
+            } else {
+                let lz = a_v.trailing_zeros();
+                Imm64::new(i64::from(lz))
+            }
+        }
+
         #[inline]
         fn imm64_sdiv(&mut self, ty: Type, x: Imm64, y: Imm64) -> Option<Imm64> {
             // Sign extend `x` and `y`.
-            let shift = u32::checked_sub(64, ty.bits()).unwrap_or(0);
-            let x = (x.bits() << shift) >> shift;
-            let y = (y.bits() << shift) >> shift;
+            let type_width = ty.bits();
+            assert!(type_width <= 64);
+            let x = x.sign_extend_from_width(type_width).bits();
+            let y = y.sign_extend_from_width(type_width).bits();
+            let shift = 64 - type_width;
 
             // NB: We can't rely on `checked_div` to detect `ty::MIN / -1`
             // (which overflows and should trap) because we are working with
@@ -44,9 +70,31 @@ macro_rules! isle_common_prelude_methods {
                 return None;
             }
 
-            let ty_mask = self.ty_mask(ty) as i64;
-            let result = x.checked_div(y)? & ty_mask;
-            Some(Imm64::new(result))
+            let result = x.checked_div(y)?;
+            Some(Imm64::new(result).mask_to_width(type_width))
+        }
+
+        #[inline]
+        fn imm64_srem(&mut self, ty: Type, x: Imm64, y: Imm64) -> Option<Imm64> {
+            // Sign extend `x` and `y`.
+            let type_width = ty.bits();
+            assert!(type_width <= 64);
+            let x = x.sign_extend_from_width(type_width).bits();
+            let y = y.sign_extend_from_width(type_width).bits();
+            let shift = 64 - type_width;
+
+            // NB: We can't rely on `checked_div` to detect `ty::MIN / -1`
+            // (which overflows and should trap) because we are working with
+            // `i64` values here, and `i32::MIN != i64::MIN`, for
+            // example. Therefore, we have to explicitly check for this case
+            // ourselves.
+            let min = ((self.ty_smin(ty) as i64) << shift) >> shift;
+            if x == min && y == -1 {
+                return None;
+            }
+
+            let result = x.checked_rem(y)?;
+            Some(Imm64::new(result).mask_to_width(type_width))
         }
 
         #[inline]

cranelift/codegen/src/opts/arithmetic.isle

@@ -125,7 +125,6 @@
 ;; x % 1 == 0
 (rule (simplify_skeleton (urem x (iconst_u ty 1))) (iconst_u ty 0))
 (rule (simplify_skeleton (srem x (iconst_u ty 1))) (iconst_u ty 0))
-(rule (simplify_skeleton (srem x (iconst_s ty -1))) (iconst_u ty 0))
 
 ;; Unsigned `x % d == x & ((1 << ilog2(d)) - 1)` when `d` is a power of two.
 (rule (simplify_skeleton (urem x (iconst_u ty (u64_extract_power_of_two d))))
@@ -339,5 +338,3 @@
 ;; (x + y) - y --> x
 (rule (simplify (isub ty (iadd ty x y) x)) y)
 (rule (simplify (isub ty (iadd ty x y) y)) x)
-
-

cranelift/codegen/src/opts/cprop.isle

@@ -1,5 +1,16 @@
 ;; Constant propagation.
 
+(rule (simplify
+      (clz (fits_in_64 ty)
+            (iconst ty kx)))
+      (subsume (iconst ty (imm64_clz ty kx))))
+
+
+(rule (simplify
+       (ctz (fits_in_64 ty)
+             (iconst ty kx)))
+      (subsume (iconst ty (imm64_ctz ty kx))))
+
 (rule (simplify
        (iadd (fits_in_64 ty)
              (iconst ty (u64_from_imm64 k1))
@@ -20,16 +31,28 @@
 
 (rule (simplify_skeleton
        (sdiv (iconst ty k1)
-             (iconst _ k2)))
+             (iconst ty k2)))
       (if-let d (imm64_sdiv ty k1 k2))
       (iconst ty d))
 
+(rule (simplify_skeleton
+       (srem (iconst ty k1)
+             (iconst ty k2)))
+      (if-let d (imm64_srem ty k1 k2))
+      (iconst ty d))
+
 (rule (simplify_skeleton
        (udiv (iconst_u ty k1)
              (iconst_u ty k2)))
       (if-let d (u64_checked_div k1 k2))
       (iconst ty (imm64_masked ty d)))
 
+(rule (simplify_skeleton
+       (urem (iconst_u ty k1)
+             (iconst_u ty k2)))
+      (if-let d (u64_checked_rem k1 k2))
+      (iconst ty (imm64_masked ty d)))
+
 (rule (simplify
        (bor (fits_in_64 ty)
             (iconst ty (u64_from_imm64 k1))

cranelift/codegen/src/prelude.isle

@@ -73,6 +73,9 @@
 (decl pure partial imm64_sdiv (Type Imm64 Imm64) Imm64)
 (extern constructor imm64_sdiv imm64_sdiv)
 
+(decl pure partial imm64_srem (Type Imm64 Imm64) Imm64)
+(extern constructor imm64_srem imm64_srem)
+
 (decl pure imm64_shl (Type Imm64 Imm64) Imm64)
 (extern constructor imm64_shl imm64_shl)
 
@@ -96,6 +99,12 @@
 (decl pure imm64_icmp (Type IntCC Imm64 Imm64) Imm64)
 (extern constructor imm64_icmp imm64_icmp)
 
+(decl pure imm64_clz (Type Imm64) Imm64)
+(extern constructor imm64_clz imm64_clz)
+
+(decl pure imm64_ctz (Type Imm64) Imm64)
+(extern constructor imm64_ctz imm64_ctz)
+
 ;; Each of these extractors tests whether the upper half of the input equals the
 ;; lower half of the input
 (decl u128_replicated_u64 (u64) u128)

cranelift/filetests/filetests/egraph/cprop.clif

@@ -22,6 +22,43 @@ block0:
 ; check: v3 = iconst.i16 -2
 ; nextln: return v3
 
+function %f0() -> i8 {
+block0:
+    v1 = iconst.i8 51
+    v2 = clz.i8 v1
+    return v2
+}
+
+function %f0() -> i16 {
+block0:
+    v1 = iconst.i16 51
+    v2 = clz.i16 v1
+    return v2
+}
+
+; check: v3 = iconst.i16 10
+; nextln: return v3
+
+function %f0() -> i16 {
+block0:
+    v1 = iconst.i16 48
+    v2 = ctz.i16 v1
+    return v2
+}
+
+; check: v3 = iconst.i16 4
+; nextln: return v3
+
+function %f0() -> i16 {
+block0:
+    v1 = iconst.i16 0
+    v2 = ctz.i16 v1
+    return v2
+}
+
+; check: v3 = iconst.i16 16
+; nextln: return v3
+
 function %ishl() -> i8 {
 block0:
     v0 = iconst.i8 1

cranelift/filetests/filetests/egraph/skeleton.clif

@@ -95,6 +95,21 @@ block0:
 ;     return v18  ; v18 = 1
 ; }
 
+function %cprop_urem() -> i32 {
+block0:
+    v0 = iconst.i32 13
+    v1 = iconst.i32 7
+    v2 = urem v0, v1
+    return v2
+}
+
+; function %cprop_urem() -> i32 fast {
+; block0:
+;     v37 = iconst.i32 6
+;     v2 -> v37
+;     return v37  ; v37 = 6
+; }
+
 function %cprop_sdiv() -> i32 {
 block0:
     v0 = iconst.i32 -7
@@ -110,6 +125,70 @@ block0:
 ;     return v11  ; v11 = -1
 ; }
 
+function %cprop_sdiv_i8_min() -> i8 {
+block0:
+    v0 = iconst.i8 -128
+    v1 = iconst.i8 -1
+    v2 = sdiv v0, v1
+    return v2
+}
+
+;function %cprop_sdiv_i8_min() -> i8 fast {
+;block0:
+;     v0 = iconst.i8 -128
+;     v1 = iconst.i8 -1
+;     v2 = sdiv v0, v1  ; v0 = -128, v1 = -1
+;     return v2
+;}
+
+function %cprop_srem_i8_min() -> i8 {
+block0:
+    v0 = iconst.i8 -128
+    v1 = iconst.i8 -1
+    v2 = srem v0, v1
+    return v2
+}
+
+;function %cprop_srem_i8_min() -> i8 fast {
+;block0:
+;     v0 = iconst.i8 -128
+;     v1 = iconst.i8 -1
+;     v2 = srem v0, v1  ; v0 = -128, v1 = -1
+;     return v2
+;}
+
+function %cprop_srem_i64_min() -> i64 {
+block0:
+    v0 = iconst.i64 -9223372036854775808
+    v1 = iconst.i64 -1
+    v2 = srem v0, v1
+    return v2
+}
+
+;function %cprop_srem_i64_min() -> i64 fast {
+;block0:
+;     v0 = iconst.i64 -9223372036854775808
+;     v1 = iconst.i64 -1
+;     v2 = srem v0, v1  ; v0 = -9223372036854775808, v1 = -1
+;     return v2
+;}
+
+function %cprop_srem() -> i32 {
+block0:
+    v0 = iconst.i32 -17
+    v1 = iconst.i32 7
+    v2 = srem v0, v1
+    return v2
+}
+
+; function %cprop_srem() -> i32 fast {
+; block0:
+;     v28 = iconst.i32 -3
+;     v2 -> v28
+;     return v28  ; v28 = -3
+; }
+
+
 function %udiv_by_one(i32) -> i32 {
 block0(v0: i32):
     v1 = iconst.i32 1
@@ -228,4 +307,3 @@ block0:
 ;     v2 = uadd_overflow_trap v0, v1, user42  ; v0 = -1, v1 = 1
 ;     return v2
 ; }
-