Rollup merge of rust-lang#40521 - TimNN:panic-free-shift, r=alexcrichton

Implemente overflowing_sh* with new unchecked_sh* intrinsics Also update some 128 bit builtins to not rely on the constant evaluator to avoid checked operations. Fixes rust-lang#40508. cc @nagisa, @alexcrichton Note: I still have a build running to see if the 128 bit changes worked (unoptimized builds take *forever* to compile), however at least the overflowing builtins no longer reference `core::panicking::panic`.
arielb1 · Mar 19, 2017 · e3cd41a · e3cd41a
2 parents 65e697b + e16d286
commit e3cd41a
Show file tree

Hide file tree

Showing 5 changed files with 127 additions and 28 deletions.
diff --git a/src/libcompiler_builtins/lib.rs b/src/libcompiler_builtins/lib.rs
@@ -34,8 +34,8 @@ pub mod reimpls {
     macro_rules! ashl {
         ($a:expr, $b:expr, $ty:ty) => {{
             let (a, b) = ($a, $b);
-            let bits = (::core::mem::size_of::<$ty>() * 8) as $ty;
-            let half_bits = bits >> 1;
+            let bits = ::core::mem::size_of::<$ty>().wrapping_mul(8) as $ty;
+            let half_bits = bits.wrapping_shr(1);
             if b & half_bits != 0 {
                 <$ty>::from_parts(0, a.low().wrapping_shl(
                                         b.wrapping_sub(half_bits) as u32))
@@ -58,8 +58,8 @@ pub mod reimpls {
     macro_rules! ashr {
         ($a: expr, $b: expr, $ty:ty) => {{
             let (a, b) = ($a, $b);
-            let bits = (::core::mem::size_of::<$ty>() * 8) as $ty;
-            let half_bits = bits >> 1;
+            let bits = ::core::mem::size_of::<$ty>().wrapping_mul(8) as $ty;
+            let half_bits = bits.wrapping_shr(1);
             if b & half_bits != 0 {
                 <$ty>::from_parts(a.high().wrapping_shr(b.wrapping_sub(half_bits) as u32)
                                   as <$ty as LargeInt>::LowHalf,
@@ -83,8 +83,8 @@ pub mod reimpls {
     macro_rules! lshr {
         ($a: expr, $b: expr, $ty:ty) => {{
             let (a, b) = ($a, $b);
-            let bits = (::core::mem::size_of::<$ty>() * 8) as $ty;
-            let half_bits = bits >> 1;
+            let bits = ::core::mem::size_of::<$ty>().wrapping_mul(8) as $ty;
+            let half_bits = bits.wrapping_shr(1);
             if b & half_bits != 0 {
                 <$ty>::from_parts(a.high().wrapping_shr(b.wrapping_sub(half_bits) as u32), 0)
             } else if b == 0 {
@@ -370,7 +370,7 @@ pub mod reimpls {
     macro_rules! mul {
         ($a:expr, $b:expr, $ty: ty, $tyh: ty) => {{
             let (a, b) = ($a, $b);
-            let half_bits = ((::core::mem::size_of::<$tyh>() * 8) / 2) as u32;
+            let half_bits = ::core::mem::size_of::<$tyh>().wrapping_mul(4) as u32;
             let lower_mask = (!0u64).wrapping_shr(half_bits);
             let mut low = (a.low() & lower_mask).wrapping_mul(b.low() & lower_mask);
             let mut t = low.wrapping_shr(half_bits);
@@ -478,7 +478,7 @@ pub mod reimpls {
             let mantissa_fraction = repr & <$fromty as FloatStuff>::MANTISSA_MASK;
             let mantissa = mantissa_fraction | <$fromty as FloatStuff>::MANTISSA_LEAD_BIT;
             if sign == -1.0 || exponent < 0 { return 0 as u128; }
-            if exponent > ::core::mem::size_of::<$outty>() as i32 * 8 {
+            if exponent > ::core::mem::size_of::<$outty>().wrapping_mul(8) as i32 {
                 return !(0 as u128);
             }
             (if exponent < (<$fromty as FloatStuff>::MANTISSA_BITS) as i32 {
@@ -503,7 +503,7 @@ pub mod reimpls {
             let mantissa = mantissa_fraction | <$fromty as FloatStuff>::MANTISSA_LEAD_BIT;
 
             if exponent < 0 { return 0 as i128; }
-            if exponent > ::core::mem::size_of::<$outty>() as i32 * 8 {
+            if exponent > ::core::mem::size_of::<$outty>().wrapping_mul(8) as i32 {
                 let ret = if sign > 0.0 { <$outty>::max_value() } else { <$outty>::min_value() };
                 return ret
             }

diff --git a/src/libcore/intrinsics.rs b/src/libcore/intrinsics.rs
@@ -1238,6 +1238,15 @@ extern "rust-intrinsic" {
     /// undefined behavior where y = 0 or x = `T::min_value()` and y = -1
     pub fn unchecked_rem<T>(x: T, y: T) -> T;
 
+    /// Performs an unchecked left shift, resulting in undefined behavior when
+    /// y < 0 or y >= N, where N is the width of T in bits.
+    #[cfg(not(stage0))]
+    pub fn unchecked_shl<T>(x: T, y: T) -> T;
+    /// Performs an unchecked right shift, resulting in undefined behavior when
+    /// y < 0 or y >= N, where N is the width of T in bits.
+    #[cfg(not(stage0))]
+    pub fn unchecked_shr<T>(x: T, y: T) -> T;
+
     /// Returns (a + b) mod 2^N, where N is the width of T in bits.
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `wrapping_add` method. For example,

diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
@@ -177,7 +177,7 @@ macro_rules! checked_op {
 
 // `Int` + `SignedInt` implemented for signed integers
 macro_rules! int_impl {
-    ($ActualT:ident, $UnsignedT:ty, $BITS:expr,
+    ($SelfT:ty, $ActualT:ident, $UnsignedT:ty, $BITS:expr,
      $add_with_overflow:path,
      $sub_with_overflow:path,
      $mul_with_overflow:path) => {
@@ -850,6 +850,17 @@ macro_rules! int_impl {
         /// ```
         #[stable(feature = "num_wrapping", since = "1.2.0")]
         #[inline(always)]
+        #[cfg(not(stage0))]
+        pub fn wrapping_shl(self, rhs: u32) -> Self {
+            unsafe {
+                intrinsics::unchecked_shl(self, (rhs & ($BITS - 1)) as $SelfT)
+            }
+        }
+
+        /// Stage 0
+        #[stable(feature = "num_wrapping", since = "1.2.0")]
+        #[inline(always)]
+        #[cfg(stage0)]
         pub fn wrapping_shl(self, rhs: u32) -> Self {
             self.overflowing_shl(rhs).0
         }
@@ -875,6 +886,17 @@ macro_rules! int_impl {
         /// ```
         #[stable(feature = "num_wrapping", since = "1.2.0")]
         #[inline(always)]
+        #[cfg(not(stage0))]
+        pub fn wrapping_shr(self, rhs: u32) -> Self {
+            unsafe {
+                intrinsics::unchecked_shr(self, (rhs & ($BITS - 1)) as $SelfT)
+            }
+        }
+
+        /// Stage 0
+        #[stable(feature = "num_wrapping", since = "1.2.0")]
+        #[inline(always)]
+        #[cfg(stage0)]
         pub fn wrapping_shr(self, rhs: u32) -> Self {
             self.overflowing_shr(rhs).0
         }
@@ -1089,6 +1111,15 @@ macro_rules! int_impl {
         /// ```
         #[inline]
         #[stable(feature = "wrapping", since = "1.7.0")]
+        #[cfg(not(stage0))]
+        pub fn overflowing_shl(self, rhs: u32) -> (Self, bool) {
+            (self.wrapping_shl(rhs), (rhs > ($BITS - 1)))
+        }
+
+        /// Stage 0
+        #[inline]
+        #[stable(feature = "wrapping", since = "1.7.0")]
+        #[cfg(stage0)]
         pub fn overflowing_shl(self, rhs: u32) -> (Self, bool) {
             (self << (rhs & ($BITS - 1)), (rhs > ($BITS - 1)))
         }
@@ -1111,6 +1142,15 @@ macro_rules! int_impl {
         /// ```
         #[inline]
         #[stable(feature = "wrapping", since = "1.7.0")]
+        #[cfg(not(stage0))]
+        pub fn overflowing_shr(self, rhs: u32) -> (Self, bool) {
+            (self.wrapping_shr(rhs), (rhs > ($BITS - 1)))
+        }
+
+        /// Stage 0
+        #[inline]
+        #[stable(feature = "wrapping", since = "1.7.0")]
+        #[cfg(stage0)]
         pub fn overflowing_shr(self, rhs: u32) -> (Self, bool) {
             (self >> (rhs & ($BITS - 1)), (rhs > ($BITS - 1)))
         }
@@ -1268,39 +1308,39 @@ macro_rules! int_impl {
 
 #[lang = "i8"]
 impl i8 {
-    int_impl! { i8, u8, 8,
+    int_impl! { i8, i8, u8, 8,
         intrinsics::add_with_overflow,
         intrinsics::sub_with_overflow,
         intrinsics::mul_with_overflow }
 }
 
 #[lang = "i16"]
 impl i16 {
-    int_impl! { i16, u16, 16,
+    int_impl! { i16, i16, u16, 16,
         intrinsics::add_with_overflow,
         intrinsics::sub_with_overflow,
         intrinsics::mul_with_overflow }
 }
 
 #[lang = "i32"]
 impl i32 {
-    int_impl! { i32, u32, 32,
+    int_impl! { i32, i32, u32, 32,
         intrinsics::add_with_overflow,
         intrinsics::sub_with_overflow,
         intrinsics::mul_with_overflow }
 }
 
 #[lang = "i64"]
 impl i64 {
-    int_impl! { i64, u64, 64,
+    int_impl! { i64, i64, u64, 64,
         intrinsics::add_with_overflow,
         intrinsics::sub_with_overflow,
         intrinsics::mul_with_overflow }
 }
 
 #[lang = "i128"]
 impl i128 {
-    int_impl! { i128, u128, 128,
+    int_impl! { i128, i128, u128, 128,
         intrinsics::add_with_overflow,
         intrinsics::sub_with_overflow,
         intrinsics::mul_with_overflow }
@@ -1309,7 +1349,7 @@ impl i128 {
 #[cfg(target_pointer_width = "16")]
 #[lang = "isize"]
 impl isize {
-    int_impl! { i16, u16, 16,
+    int_impl! { isize, i16, u16, 16,
         intrinsics::add_with_overflow,
         intrinsics::sub_with_overflow,
         intrinsics::mul_with_overflow }
@@ -1318,7 +1358,7 @@ impl isize {
 #[cfg(target_pointer_width = "32")]
 #[lang = "isize"]
 impl isize {
-    int_impl! { i32, u32, 32,
+    int_impl! { isize, i32, u32, 32,
         intrinsics::add_with_overflow,
         intrinsics::sub_with_overflow,
         intrinsics::mul_with_overflow }
@@ -1327,15 +1367,15 @@ impl isize {
 #[cfg(target_pointer_width = "64")]
 #[lang = "isize"]
 impl isize {
-    int_impl! { i64, u64, 64,
+    int_impl! { isize, i64, u64, 64,
         intrinsics::add_with_overflow,
         intrinsics::sub_with_overflow,
         intrinsics::mul_with_overflow }
 }
 
 // `Int` + `UnsignedInt` implemented for unsigned integers
 macro_rules! uint_impl {
-    ($ActualT:ty, $BITS:expr,
+    ($SelfT:ty, $ActualT:ty, $BITS:expr,
      $ctpop:path,
      $ctlz:path,
      $cttz:path,
@@ -1978,6 +2018,17 @@ macro_rules! uint_impl {
         /// ```
         #[stable(feature = "num_wrapping", since = "1.2.0")]
         #[inline(always)]
+        #[cfg(not(stage0))]
+        pub fn wrapping_shl(self, rhs: u32) -> Self {
+            unsafe {
+                intrinsics::unchecked_shl(self, (rhs & ($BITS - 1)) as $SelfT)
+            }
+        }
+
+        /// Stage 0
+        #[stable(feature = "num_wrapping", since = "1.2.0")]
+        #[inline(always)]
+        #[cfg(stage0)]
         pub fn wrapping_shl(self, rhs: u32) -> Self {
             self.overflowing_shl(rhs).0
         }
@@ -2003,6 +2054,17 @@ macro_rules! uint_impl {
         /// ```
         #[stable(feature = "num_wrapping", since = "1.2.0")]
         #[inline(always)]
+        #[cfg(not(stage0))]
+        pub fn wrapping_shr(self, rhs: u32) -> Self {
+            unsafe {
+                intrinsics::unchecked_shr(self, (rhs & ($BITS - 1)) as $SelfT)
+            }
+        }
+
+        /// Stage 0
+        #[stable(feature = "num_wrapping", since = "1.2.0")]
+        #[inline(always)]
+        #[cfg(stage0)]
         pub fn wrapping_shr(self, rhs: u32) -> Self {
             self.overflowing_shr(rhs).0
         }
@@ -2170,6 +2232,15 @@ macro_rules! uint_impl {
         /// ```
         #[inline]
         #[stable(feature = "wrapping", since = "1.7.0")]
+        #[cfg(not(stage0))]
+        pub fn overflowing_shl(self, rhs: u32) -> (Self, bool) {
+            (self.wrapping_shl(rhs), (rhs > ($BITS - 1)))
+        }
+
+        /// Stage 0
+        #[inline]
+        #[stable(feature = "wrapping", since = "1.7.0")]
+        #[cfg(stage0)]
         pub fn overflowing_shl(self, rhs: u32) -> (Self, bool) {
             (self << (rhs & ($BITS - 1)), (rhs > ($BITS - 1)))
         }
@@ -2192,6 +2263,16 @@ macro_rules! uint_impl {
         /// ```
         #[inline]
         #[stable(feature = "wrapping", since = "1.7.0")]
+        #[cfg(not(stage0))]
+        pub fn overflowing_shr(self, rhs: u32) -> (Self, bool) {
+            (self.wrapping_shr(rhs), (rhs > ($BITS - 1)))
+
+        }
+
+        /// Stage 0
+        #[inline]
+        #[stable(feature = "wrapping", since = "1.7.0")]
+        #[cfg(stage0)]
         pub fn overflowing_shr(self, rhs: u32) -> (Self, bool) {
             (self >> (rhs & ($BITS - 1)), (rhs > ($BITS - 1)))
         }
@@ -2292,7 +2373,7 @@ macro_rules! uint_impl {
 
 #[lang = "u8"]
 impl u8 {
-    uint_impl! { u8, 8,
+    uint_impl! { u8, u8, 8,
         intrinsics::ctpop,
         intrinsics::ctlz,
         intrinsics::cttz,
@@ -2304,7 +2385,7 @@ impl u8 {
 
 #[lang = "u16"]
 impl u16 {
-    uint_impl! { u16, 16,
+    uint_impl! { u16, u16, 16,
         intrinsics::ctpop,
         intrinsics::ctlz,
         intrinsics::cttz,
@@ -2316,7 +2397,7 @@ impl u16 {
 
 #[lang = "u32"]
 impl u32 {
-    uint_impl! { u32, 32,
+    uint_impl! { u32, u32, 32,
         intrinsics::ctpop,
         intrinsics::ctlz,
         intrinsics::cttz,
@@ -2328,7 +2409,7 @@ impl u32 {
 
 #[lang = "u64"]
 impl u64 {
-    uint_impl! { u64, 64,
+    uint_impl! { u64, u64, 64,
         intrinsics::ctpop,
         intrinsics::ctlz,
         intrinsics::cttz,
@@ -2340,7 +2421,7 @@ impl u64 {
 
 #[lang = "u128"]
 impl u128 {
-    uint_impl! { u128, 128,
+    uint_impl! { u128, u128, 128,
         intrinsics::ctpop,
         intrinsics::ctlz,
         intrinsics::cttz,
@@ -2353,7 +2434,7 @@ impl u128 {
 #[cfg(target_pointer_width = "16")]
 #[lang = "usize"]
 impl usize {
-    uint_impl! { u16, 16,
+    uint_impl! { usize, u16, 16,
         intrinsics::ctpop,
         intrinsics::ctlz,
         intrinsics::cttz,
@@ -2365,7 +2446,7 @@ impl usize {
 #[cfg(target_pointer_width = "32")]
 #[lang = "usize"]
 impl usize {
-    uint_impl! { u32, 32,
+    uint_impl! { usize, u32, 32,
         intrinsics::ctpop,
         intrinsics::ctlz,
         intrinsics::cttz,
@@ -2378,7 +2459,7 @@ impl usize {
 #[cfg(target_pointer_width = "64")]
 #[lang = "usize"]
 impl usize {
-    uint_impl! { u64, 64,
+    uint_impl! { usize, u64, 64,
         intrinsics::ctpop,
         intrinsics::ctlz,
         intrinsics::cttz,

diff --git a/src/librustc_trans/intrinsic.rs b/src/librustc_trans/intrinsic.rs
@@ -261,7 +261,7 @@ pub fn trans_intrinsic_call<'a, 'tcx>(bcx: &Builder<'a, 'tcx>,
         "ctlz" | "cttz" | "ctpop" | "bswap" |
         "add_with_overflow" | "sub_with_overflow" | "mul_with_overflow" |
         "overflowing_add" | "overflowing_sub" | "overflowing_mul" |
-        "unchecked_div" | "unchecked_rem" => {
+        "unchecked_div" | "unchecked_rem" | "unchecked_shl" | "unchecked_shr" => {
             let sty = &arg_tys[0].sty;
             match int_type_width_signed(sty, ccx) {
                 Some((width, signed)) =>
@@ -311,6 +311,13 @@ pub fn trans_intrinsic_call<'a, 'tcx>(bcx: &Builder<'a, 'tcx>,
                             } else {
                                 bcx.urem(llargs[0], llargs[1])
                             },
+                        "unchecked_shl" => bcx.shl(llargs[0], llargs[1]),
+                        "unchecked_shr" =>
+                            if signed {
+                                bcx.ashr(llargs[0], llargs[1])
+                            } else {
+                                bcx.lshr(llargs[0], llargs[1])
+                            },
                         _ => bug!(),
                     },
                 None => {