From 6ac035df442a27cf9e99ab4ec25bb6147a700902 Mon Sep 17 00:00:00 2001 From: Oli Scherer Date: Thu, 1 Feb 2024 22:53:25 +0000 Subject: [PATCH] Revert unsound libcore changes of #119911 --- library/core/src/lib.rs | 1 - library/core/src/num/int_macros.rs | 284 ++++++++-------------------- library/core/src/num/uint_macros.rs | 249 ++++++++---------------- tests/codegen/pow_of_two.rs | 55 ------ 4 files changed, 149 insertions(+), 440 deletions(-) delete mode 100644 tests/codegen/pow_of_two.rs diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs index 2af242d4b5071..ead8cbe0e2f43 100644 --- a/library/core/src/lib.rs +++ b/library/core/src/lib.rs @@ -200,7 +200,6 @@ // // Language features: // tidy-alphabetical-start -#![cfg_attr(not(bootstrap), feature(is_val_statically_known))] #![feature(abi_unadjusted)] #![feature(adt_const_params)] #![feature(allow_internal_unsafe)] diff --git a/library/core/src/num/int_macros.rs b/library/core/src/num/int_macros.rs index bb35b6128ea5a..d052dcc3e6ee6 100644 --- a/library/core/src/num/int_macros.rs +++ b/library/core/src/num/int_macros.rs @@ -1374,59 +1374,26 @@ macro_rules! int_impl { #[rustc_const_stable(feature = "const_int_pow", since = "1.50.0")] #[must_use = "this returns the result of the operation, \ without modifying the original"] - #[rustc_allow_const_fn_unstable(is_val_statically_known, const_int_unchecked_arith)] #[inline] pub const fn checked_pow(self, mut exp: u32) -> Option { - // SAFETY: This path has the same behavior as the other. - if unsafe { intrinsics::is_val_statically_known(self) } - && self.unsigned_abs().is_power_of_two() - { - if self == 1 { // Avoid divide by zero - return Some(1); - } - if self == -1 { // Avoid divide by zero - return Some(if exp & 1 != 0 { -1 } else { 1 }); - } - // SAFETY: We just checked this is a power of two. and above zero. - let power_used = unsafe { intrinsics::cttz_nonzero(self.wrapping_abs()) as u32 }; - if exp > Self::BITS / power_used { return None; } // Division of constants is free - - // SAFETY: exp <= Self::BITS / power_used - let res = unsafe { intrinsics::unchecked_shl( - 1 as Self, - intrinsics::unchecked_mul(power_used, exp) as Self - )}; - // LLVM doesn't always optimize out the checks - // at the ir level. - - let sign = self.is_negative() && exp & 1 != 0; - if !sign && res == Self::MIN { - None - } else if sign { - Some(res.wrapping_neg()) - } else { - Some(res) - } - } else { - if exp == 0 { - return Some(1); - } - let mut base = self; - let mut acc: Self = 1; - - while exp > 1 { - if (exp & 1) == 1 { - acc = try_opt!(acc.checked_mul(base)); - } - exp /= 2; - base = try_opt!(base.checked_mul(base)); + if exp == 0 { + return Some(1); + } + let mut base = self; + let mut acc: Self = 1; + + while exp > 1 { + if (exp & 1) == 1 { + acc = try_opt!(acc.checked_mul(base)); } - // since exp!=0, finally the exp must be 1. - // Deal with the final bit of the exponent separately, since - // squaring the base afterwards is not necessary and may cause a - // needless overflow. - acc.checked_mul(base) + exp /= 2; + base = try_opt!(base.checked_mul(base)); } + // since exp!=0, finally the exp must be 1. + // Deal with the final bit of the exponent separately, since + // squaring the base afterwards is not necessary and may cause a + // needless overflow. + acc.checked_mul(base) } /// Strict exponentiation. Computes `self.pow(exp)`, panicking if @@ -2091,58 +2058,27 @@ macro_rules! int_impl { #[rustc_const_stable(feature = "const_int_pow", since = "1.50.0")] #[must_use = "this returns the result of the operation, \ without modifying the original"] - #[rustc_allow_const_fn_unstable(is_val_statically_known, const_int_unchecked_arith)] #[inline] pub const fn wrapping_pow(self, mut exp: u32) -> Self { - // SAFETY: This path has the same behavior as the other. - if unsafe { intrinsics::is_val_statically_known(self) } - && self.unsigned_abs().is_power_of_two() - { - if self == 1 { // Avoid divide by zero - return 1; - } - if self == -1 { // Avoid divide by zero - return if exp & 1 != 0 { -1 } else { 1 }; - } - // SAFETY: We just checked this is a power of two. and above zero. - let power_used = unsafe { intrinsics::cttz_nonzero(self.wrapping_abs()) as u32 }; - if exp > Self::BITS / power_used { return 0; } // Division of constants is free - - // SAFETY: exp <= Self::BITS / power_used - let res = unsafe { intrinsics::unchecked_shl( - 1 as Self, - intrinsics::unchecked_mul(power_used, exp) as Self - )}; - // LLVM doesn't always optimize out the checks - // at the ir level. - - let sign = self.is_negative() && exp & 1 != 0; - if sign { - res.wrapping_neg() - } else { - res - } - } else { - if exp == 0 { - return 1; - } - let mut base = self; - let mut acc: Self = 1; - - while exp > 1 { - if (exp & 1) == 1 { - acc = acc.wrapping_mul(base); - } - exp /= 2; - base = base.wrapping_mul(base); - } + if exp == 0 { + return 1; + } + let mut base = self; + let mut acc: Self = 1; - // since exp!=0, finally the exp must be 1. - // Deal with the final bit of the exponent separately, since - // squaring the base afterwards is not necessary and may cause a - // needless overflow. - acc.wrapping_mul(base) + while exp > 1 { + if (exp & 1) == 1 { + acc = acc.wrapping_mul(base); + } + exp /= 2; + base = base.wrapping_mul(base); } + + // since exp!=0, finally the exp must be 1. + // Deal with the final bit of the exponent separately, since + // squaring the base afterwards is not necessary and may cause a + // needless overflow. + acc.wrapping_mul(base) } /// Calculates `self` + `rhs` @@ -2625,68 +2561,36 @@ macro_rules! int_impl { #[rustc_const_stable(feature = "const_int_pow", since = "1.50.0")] #[must_use = "this returns the result of the operation, \ without modifying the original"] - #[rustc_allow_const_fn_unstable(is_val_statically_known, const_int_unchecked_arith)] #[inline] pub const fn overflowing_pow(self, mut exp: u32) -> (Self, bool) { - // SAFETY: This path has the same behavior as the other. - if unsafe { intrinsics::is_val_statically_known(self) } - && self.unsigned_abs().is_power_of_two() - { - if self == 1 { // Avoid divide by zero - return (1, false); - } - if self == -1 { // Avoid divide by zero - return (if exp & 1 != 0 { -1 } else { 1 }, false); - } - // SAFETY: We just checked this is a power of two. and above zero. - let power_used = unsafe { intrinsics::cttz_nonzero(self.wrapping_abs()) as u32 }; - if exp > Self::BITS / power_used { return (0, true); } // Division of constants is free - - // SAFETY: exp <= Self::BITS / power_used - let res = unsafe { intrinsics::unchecked_shl( - 1 as Self, - intrinsics::unchecked_mul(power_used, exp) as Self - )}; - // LLVM doesn't always optimize out the checks - // at the ir level. - - let sign = self.is_negative() && exp & 1 != 0; - let overflow = res == Self::MIN; - if sign { - (res.wrapping_neg(), overflow) - } else { - (res, overflow) - } - } else { - if exp == 0 { - return (1,false); - } - let mut base = self; - let mut acc: Self = 1; - let mut overflown = false; - // Scratch space for storing results of overflowing_mul. - let mut r; - - while exp > 1 { - if (exp & 1) == 1 { - r = acc.overflowing_mul(base); - acc = r.0; - overflown |= r.1; - } - exp /= 2; - r = base.overflowing_mul(base); - base = r.0; + if exp == 0 { + return (1,false); + } + let mut base = self; + let mut acc: Self = 1; + let mut overflown = false; + // Scratch space for storing results of overflowing_mul. + let mut r; + + while exp > 1 { + if (exp & 1) == 1 { + r = acc.overflowing_mul(base); + acc = r.0; overflown |= r.1; } - - // since exp!=0, finally the exp must be 1. - // Deal with the final bit of the exponent separately, since - // squaring the base afterwards is not necessary and may cause a - // needless overflow. - r = acc.overflowing_mul(base); - r.1 |= overflown; - r + exp /= 2; + r = base.overflowing_mul(base); + base = r.0; + overflown |= r.1; } + + // since exp!=0, finally the exp must be 1. + // Deal with the final bit of the exponent separately, since + // squaring the base afterwards is not necessary and may cause a + // needless overflow. + r = acc.overflowing_mul(base); + r.1 |= overflown; + r } /// Raises self to the power of `exp`, using exponentiation by squaring. @@ -2704,68 +2608,28 @@ macro_rules! int_impl { #[rustc_const_stable(feature = "const_int_pow", since = "1.50.0")] #[must_use = "this returns the result of the operation, \ without modifying the original"] - #[rustc_allow_const_fn_unstable(is_val_statically_known, const_int_unchecked_arith)] #[inline] #[rustc_inherit_overflow_checks] - #[track_caller] // Hides the hackish overflow check for powers of two. pub const fn pow(self, mut exp: u32) -> Self { - // SAFETY: This path has the same behavior as the other. - if unsafe { intrinsics::is_val_statically_known(self) } - && self.unsigned_abs().is_power_of_two() - { - if self == 1 { // Avoid divide by zero - return 1; - } - if self == -1 { // Avoid divide by zero - return if exp & 1 != 0 { -1 } else { 1 }; - } - // SAFETY: We just checked this is a power of two. and above zero. - let power_used = unsafe { intrinsics::cttz_nonzero(self.wrapping_abs()) as u32 }; - if exp > Self::BITS / power_used { // Division of constants is free - #[allow(arithmetic_overflow)] - return Self::MAX * Self::MAX * 0; - } + if exp == 0 { + return 1; + } + let mut base = self; + let mut acc = 1; - // SAFETY: exp <= Self::BITS / power_used - let res = unsafe { intrinsics::unchecked_shl( - 1 as Self, - intrinsics::unchecked_mul(power_used, exp) as Self - )}; - // LLVM doesn't always optimize out the checks - // at the ir level. - - let sign = self.is_negative() && exp & 1 != 0; - #[allow(arithmetic_overflow)] - if !sign && res == Self::MIN { - // So it panics. - _ = Self::MAX * Self::MAX; - } - if sign { - res.wrapping_neg() - } else { - res - } - } else { - if exp == 0 { - return 1; - } - let mut base = self; - let mut acc = 1; - - while exp > 1 { - if (exp & 1) == 1 { - acc = acc * base; - } - exp /= 2; - base = base * base; + while exp > 1 { + if (exp & 1) == 1 { + acc = acc * base; } - - // since exp!=0, finally the exp must be 1. - // Deal with the final bit of the exponent separately, since - // squaring the base afterwards is not necessary and may cause a - // needless overflow. - acc * base + exp /= 2; + base = base * base; } + + // since exp!=0, finally the exp must be 1. + // Deal with the final bit of the exponent separately, since + // squaring the base afterwards is not necessary and may cause a + // needless overflow. + acc * base } /// Returns the square root of the number, rounded down. diff --git a/library/core/src/num/uint_macros.rs b/library/core/src/num/uint_macros.rs index d450c68a5b230..a217c2e259d2b 100644 --- a/library/core/src/num/uint_macros.rs +++ b/library/core/src/num/uint_macros.rs @@ -1364,49 +1364,28 @@ macro_rules! uint_impl { #[rustc_const_stable(feature = "const_int_pow", since = "1.50.0")] #[must_use = "this returns the result of the operation, \ without modifying the original"] - #[rustc_allow_const_fn_unstable(is_val_statically_known, const_int_unchecked_arith)] #[inline] pub const fn checked_pow(self, mut exp: u32) -> Option { - // SAFETY: This path has the same behavior as the other. - if unsafe { intrinsics::is_val_statically_known(self) } - && self.is_power_of_two() - { - if self == 1 { // Avoid divide by zero - return Some(1); - } - // SAFETY: We just checked this is a power of two. and above zero. - let power_used = unsafe { intrinsics::cttz_nonzero(self) as u32 }; - if exp > Self::BITS / power_used { return None; } // Division of constants is free - - // SAFETY: exp <= Self::BITS / power_used - unsafe { Some(intrinsics::unchecked_shl( - 1 as Self, - intrinsics::unchecked_mul(power_used, exp) as Self - )) } - // LLVM doesn't always optimize out the checks - // at the ir level. - } else { - if exp == 0 { - return Some(1); - } - let mut base = self; - let mut acc: Self = 1; - - while exp > 1 { - if (exp & 1) == 1 { - acc = try_opt!(acc.checked_mul(base)); - } - exp /= 2; - base = try_opt!(base.checked_mul(base)); + if exp == 0 { + return Some(1); + } + let mut base = self; + let mut acc: Self = 1; + + while exp > 1 { + if (exp & 1) == 1 { + acc = try_opt!(acc.checked_mul(base)); } + exp /= 2; + base = try_opt!(base.checked_mul(base)); + } - // since exp!=0, finally the exp must be 1. - // Deal with the final bit of the exponent separately, since - // squaring the base afterwards is not necessary and may cause a - // needless overflow. + // since exp!=0, finally the exp must be 1. + // Deal with the final bit of the exponent separately, since + // squaring the base afterwards is not necessary and may cause a + // needless overflow. - acc.checked_mul(base) - } + acc.checked_mul(base) } /// Strict exponentiation. Computes `self.pow(exp)`, panicking if @@ -1908,48 +1887,27 @@ macro_rules! uint_impl { #[rustc_const_stable(feature = "const_int_pow", since = "1.50.0")] #[must_use = "this returns the result of the operation, \ without modifying the original"] - #[rustc_allow_const_fn_unstable(is_val_statically_known, const_int_unchecked_arith)] #[inline] pub const fn wrapping_pow(self, mut exp: u32) -> Self { - // SAFETY: This path has the same behavior as the other. - if unsafe { intrinsics::is_val_statically_known(self) } - && self.is_power_of_two() - { - if self == 1 { // Avoid divide by zero - return 1; - } - // SAFETY: We just checked this is a power of two. and above zero. - let power_used = unsafe { intrinsics::cttz_nonzero(self) as u32 }; - if exp > Self::BITS / power_used { return 0; } // Division of constants is free - - // SAFETY: exp <= Self::BITS / power_used - unsafe { intrinsics::unchecked_shl( - 1 as Self, - intrinsics::unchecked_mul(power_used, exp) as Self - )} - // LLVM doesn't always optimize out the checks - // at the ir level. - } else { - if exp == 0 { - return 1; - } - let mut base = self; - let mut acc: Self = 1; - - while exp > 1 { - if (exp & 1) == 1 { - acc = acc.wrapping_mul(base); - } - exp /= 2; - base = base.wrapping_mul(base); - } + if exp == 0 { + return 1; + } + let mut base = self; + let mut acc: Self = 1; - // since exp!=0, finally the exp must be 1. - // Deal with the final bit of the exponent separately, since - // squaring the base afterwards is not necessary and may cause a - // needless overflow. - acc.wrapping_mul(base) + while exp > 1 { + if (exp & 1) == 1 { + acc = acc.wrapping_mul(base); + } + exp /= 2; + base = base.wrapping_mul(base); } + + // since exp!=0, finally the exp must be 1. + // Deal with the final bit of the exponent separately, since + // squaring the base afterwards is not necessary and may cause a + // needless overflow. + acc.wrapping_mul(base) } /// Calculates `self` + `rhs` @@ -2383,58 +2341,37 @@ macro_rules! uint_impl { #[rustc_const_stable(feature = "const_int_pow", since = "1.50.0")] #[must_use = "this returns the result of the operation, \ without modifying the original"] - #[rustc_allow_const_fn_unstable(is_val_statically_known, const_int_unchecked_arith)] #[inline] pub const fn overflowing_pow(self, mut exp: u32) -> (Self, bool) { - // SAFETY: This path has the same behavior as the other. - if unsafe { intrinsics::is_val_statically_known(self) } - && self.is_power_of_two() - { - if self == 1 { // Avoid divide by zero - return (1, false); - } - // SAFETY: We just checked this is a power of two. and above zero. - let power_used = unsafe { intrinsics::cttz_nonzero(self) as u32 }; - if exp > Self::BITS / power_used { return (0, true); } // Division of constants is free - - // SAFETY: exp <= Self::BITS / power_used - unsafe { (intrinsics::unchecked_shl( - 1 as Self, - intrinsics::unchecked_mul(power_used, exp) as Self - ), false) } - // LLVM doesn't always optimize out the checks - // at the ir level. - } else { - if exp == 0{ - return (1,false); - } - let mut base = self; - let mut acc: Self = 1; - let mut overflown = false; - // Scratch space for storing results of overflowing_mul. - let mut r; - - while exp > 1 { - if (exp & 1) == 1 { - r = acc.overflowing_mul(base); - acc = r.0; - overflown |= r.1; - } - exp /= 2; - r = base.overflowing_mul(base); - base = r.0; + if exp == 0{ + return (1,false); + } + let mut base = self; + let mut acc: Self = 1; + let mut overflown = false; + // Scratch space for storing results of overflowing_mul. + let mut r; + + while exp > 1 { + if (exp & 1) == 1 { + r = acc.overflowing_mul(base); + acc = r.0; overflown |= r.1; } + exp /= 2; + r = base.overflowing_mul(base); + base = r.0; + overflown |= r.1; + } - // since exp!=0, finally the exp must be 1. - // Deal with the final bit of the exponent separately, since - // squaring the base afterwards is not necessary and may cause a - // needless overflow. - r = acc.overflowing_mul(base); - r.1 |= overflown; + // since exp!=0, finally the exp must be 1. + // Deal with the final bit of the exponent separately, since + // squaring the base afterwards is not necessary and may cause a + // needless overflow. + r = acc.overflowing_mul(base); + r.1 |= overflown; - r - } + r } /// Raises self to the power of `exp`, using exponentiation by squaring. @@ -2450,64 +2387,28 @@ macro_rules! uint_impl { #[rustc_const_stable(feature = "const_int_pow", since = "1.50.0")] #[must_use = "this returns the result of the operation, \ without modifying the original"] - #[rustc_allow_const_fn_unstable(is_val_statically_known, const_int_unchecked_arith)] #[inline] #[rustc_inherit_overflow_checks] - #[track_caller] // Hides the hackish overflow check for powers of two. pub const fn pow(self, mut exp: u32) -> Self { - // LLVM now knows that `self` is a constant value, but not a - // constant in Rust. This allows us to compute the power used at - // compile-time. - // - // This will likely add a branch in debug builds, but this should - // be ok. - // - // This is a massive performance boost in release builds as you can - // get the power of a power of two and the exponent through a `shl` - // instruction, but we must add a couple more checks for parity with - // our own `pow`. - // SAFETY: This path has the same behavior as the other. - if unsafe { intrinsics::is_val_statically_known(self) } - && self.is_power_of_two() - { - if self == 1 { // Avoid divide by zero - return 1; - } - // SAFETY: We just checked this is a power of two. and above zero. - let power_used = unsafe { intrinsics::cttz_nonzero(self) as u32 }; - if exp > Self::BITS / power_used { // Division of constants is free - #[allow(arithmetic_overflow)] - return Self::MAX * Self::MAX * 0; - } + if exp == 0 { + return 1; + } + let mut base = self; + let mut acc = 1; - // SAFETY: exp <= Self::BITS / power_used - unsafe { intrinsics::unchecked_shl( - 1 as Self, - intrinsics::unchecked_mul(power_used, exp) as Self - )} - // LLVM doesn't always optimize out the checks - // at the ir level. - } else { - if exp == 0 { - return 1; - } - let mut base = self; - let mut acc = 1; - - while exp > 1 { - if (exp & 1) == 1 { - acc = acc * base; - } - exp /= 2; - base = base * base; + while exp > 1 { + if (exp & 1) == 1 { + acc = acc * base; } - - // since exp!=0, finally the exp must be 1. - // Deal with the final bit of the exponent separately, since - // squaring the base afterwards is not necessary and may cause a - // needless overflow. - acc * base + exp /= 2; + base = base * base; } + + // since exp!=0, finally the exp must be 1. + // Deal with the final bit of the exponent separately, since + // squaring the base afterwards is not necessary and may cause a + // needless overflow. + acc * base } /// Returns the square root of the number, rounded down. diff --git a/tests/codegen/pow_of_two.rs b/tests/codegen/pow_of_two.rs deleted file mode 100644 index 372360dfd12c7..0000000000000 --- a/tests/codegen/pow_of_two.rs +++ /dev/null @@ -1,55 +0,0 @@ -// compile-flags: --crate-type=lib -Zmerge-functions=disabled -O -C overflow-checks=false - -// CHECK-LABEL: @a( -#[no_mangle] -pub fn a(exp: u32) -> u64 { - // CHECK: %{{[^ ]+}} = icmp ugt i32 %exp, 64 - // CHECK: %{{[^ ]+}} = zext{{( nneg)?}} i32 %exp to i64 - // CHECK: %{{[^ ]+}} = shl nuw i64 {{[^ ]+}}, %{{[^ ]+}} - // CHECK: ret i64 %{{[^ ]+}} - 2u64.pow(exp) -} - -// CHECK-LABEL: @b( -#[no_mangle] -pub fn b(exp: u32) -> i64 { - // CHECK: %{{[^ ]+}} = icmp ugt i32 %exp, 64 - // CHECK: %{{[^ ]+}} = zext{{( nneg)?}} i32 %exp to i64 - // CHECK: %{{[^ ]+}} = shl nuw i64 {{[^ ]+}}, %{{[^ ]+}} - // CHECK: ret i64 %{{[^ ]+}} - 2i64.pow(exp) -} - -// CHECK-LABEL: @c( -#[no_mangle] -pub fn c(exp: u32) -> u32 { - // CHECK: %{{[^ ]+}} = icmp ugt i32 %exp, 16 - // CHECK: %{{[^ ]+}} = shl nuw nsw i32 %exp, 1 - // CHECK: %{{[^ ]+}} = shl nuw i32 1, %{{[^ ]+}} - // CHECK: %{{[^ ]+}} = select i1 %{{[^ ]+}}, i32 0, i32 %{{[^ ]+}} - // CHECK: ret i32 %{{[^ ]+}} - 4u32.pow(exp) -} - -// CHECK-LABEL: @d( -#[no_mangle] -pub fn d(exp: u32) -> u32 { - // CHECK: %{{[^ ]+}} = icmp ugt i32 %exp, 6 - // CHECK: %{{[^ ]+}} = mul nuw nsw i32 %exp, 5 - // CHECK: %{{[^ ]+}} = shl nuw nsw i32 1, %{{[^ ]+}} - // CHECK: %{{[^ ]+}} = select i1 {{[^ ]+}}, i32 0, i32 %{{[^ ]+}} - // CHECK: ret i32 %{{[^ ]+}} - 32u32.pow(exp) -} - -// CHECK-LABEL: @e( -#[no_mangle] -pub fn e(exp: u32) -> i32 { - // CHECK: %{{[^ ]+}} = icmp ugt i32 %exp, 6 - // CHECK: %{{[^ ]+}} = mul nuw {{(nsw )?}}i32 %exp, 5 - // CHECK: %{{[^ ]+}} = shl nuw {{(nsw )?}}i32 1, %{{[^ ]+}} - // CHECK: %{{[^ ]+}} = select i1 {{[^ ]+}}, i32 0, i32 %{{[^ ]+}} - // CHECK: ret i32 %{{[^ ]+}} - 32i32.pow(exp) -} -// note: d and e are expected to yield the same IR