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Auto merge of rust-lang#128371 - andjo403:rangeAttribute, r=nikic
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Add range attribute to scalar function results and arguments

as LLVM 19 adds the range attribute this starts to use it for better optimization.
hade been interesting to see a perf run with the rust-lang#127513

closes rust-lang#50156
cc rust-lang#49572 shall be fixed but not possible to see as there is asserts that already trigger the optimization.

r​? `@nikic`
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bors committed Aug 9, 2024
2 parents 97e7252 + aef6352 commit f11897f
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Showing 12 changed files with 159 additions and 24 deletions.
61 changes: 48 additions & 13 deletions compiler/rustc_codegen_llvm/src/abi.rs
Original file line number Diff line number Diff line change
Expand Up @@ -430,9 +430,32 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
i += 1;
i - 1
};

let apply_range_attr = |idx: AttributePlace, scalar: rustc_target::abi::Scalar| {
if cx.sess().opts.optimize != config::OptLevel::No
&& llvm_util::get_version() >= (19, 0, 0)
&& matches!(scalar.primitive(), Int(..))
// If the value is a boolean, the range is 0..2 and that ultimately
// become 0..0 when the type becomes i1, which would be rejected
// by the LLVM verifier.
&& !scalar.is_bool()
// LLVM also rejects full range.
&& !scalar.is_always_valid(cx)
{
attributes::apply_to_llfn(
llfn,
idx,
&[llvm::CreateRangeAttr(cx.llcx, scalar.size(cx), scalar.valid_range(cx))],
);
}
};

match &self.ret.mode {
PassMode::Direct(attrs) => {
attrs.apply_attrs_to_llfn(llvm::AttributePlace::ReturnValue, cx, llfn);
if let abi::Abi::Scalar(scalar) = self.ret.layout.abi {
apply_range_attr(llvm::AttributePlace::ReturnValue, scalar);
}
}
PassMode::Indirect { attrs, meta_attrs: _, on_stack } => {
assert!(!on_stack);
Expand Down Expand Up @@ -471,8 +494,13 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
);
attributes::apply_to_llfn(llfn, llvm::AttributePlace::Argument(i), &[byval]);
}
PassMode::Direct(attrs)
| PassMode::Indirect { attrs, meta_attrs: None, on_stack: false } => {
PassMode::Direct(attrs) => {
let i = apply(attrs);
if let abi::Abi::Scalar(scalar) = arg.layout.abi {
apply_range_attr(llvm::AttributePlace::Argument(i), scalar);
}
}
PassMode::Indirect { attrs, meta_attrs: None, on_stack: false } => {
apply(attrs);
}
PassMode::Indirect { attrs, meta_attrs: Some(meta_attrs), on_stack } => {
Expand All @@ -481,8 +509,12 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
apply(meta_attrs);
}
PassMode::Pair(a, b) => {
apply(a);
apply(b);
let i = apply(a);
let ii = apply(b);
if let abi::Abi::ScalarPair(scalar_a, scalar_b) = arg.layout.abi {
apply_range_attr(llvm::AttributePlace::Argument(i), scalar_a);
apply_range_attr(llvm::AttributePlace::Argument(ii), scalar_b);
}
}
PassMode::Cast { cast, pad_i32 } => {
if *pad_i32 {
Expand Down Expand Up @@ -537,15 +569,18 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
}
_ => {}
}
if let abi::Abi::Scalar(scalar) = self.ret.layout.abi {
// If the value is a boolean, the range is 0..2 and that ultimately
// become 0..0 when the type becomes i1, which would be rejected
// by the LLVM verifier.
if let Int(..) = scalar.primitive() {
if !scalar.is_bool() && !scalar.is_always_valid(bx) {
bx.range_metadata(callsite, scalar.valid_range(bx));
}
}
if bx.cx.sess().opts.optimize != config::OptLevel::No
&& llvm_util::get_version() < (19, 0, 0)
&& let abi::Abi::Scalar(scalar) = self.ret.layout.abi
&& matches!(scalar.primitive(), Int(..))
// If the value is a boolean, the range is 0..2 and that ultimately
// become 0..0 when the type becomes i1, which would be rejected
// by the LLVM verifier.
&& !scalar.is_bool()
// LLVM also rejects full range.
&& !scalar.is_always_valid(bx)
{
bx.range_metadata(callsite, scalar.valid_range(bx));
}
for arg in self.args.iter() {
match &arg.mode {
Expand Down
6 changes: 6 additions & 0 deletions compiler/rustc_codegen_llvm/src/llvm/ffi.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1575,6 +1575,12 @@ extern "C" {
pub fn LLVMRustCreateAllocSizeAttr(C: &Context, size_arg: u32) -> &Attribute;
pub fn LLVMRustCreateAllocKindAttr(C: &Context, size_arg: u64) -> &Attribute;
pub fn LLVMRustCreateMemoryEffectsAttr(C: &Context, effects: MemoryEffects) -> &Attribute;
pub fn LLVMRustCreateRangeAttribute(
C: &Context,
num_bits: c_uint,
lower_words: *const u64,
upper_words: *const u64,
) -> &Attribute;

// Operations on functions
pub fn LLVMRustGetOrInsertFunction<'a>(
Expand Down
17 changes: 16 additions & 1 deletion compiler/rustc_codegen_llvm/src/llvm/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@ use std::string::FromUtf8Error;
use libc::c_uint;
use rustc_data_structures::small_c_str::SmallCStr;
use rustc_llvm::RustString;
use rustc_target::abi::Align;
use rustc_target::abi::{Align, Size, WrappingRange};

pub use self::AtomicRmwBinOp::*;
pub use self::CallConv::*;
Expand Down Expand Up @@ -105,6 +105,21 @@ pub fn CreateAllocKindAttr(llcx: &Context, kind_arg: AllocKindFlags) -> &Attribu
unsafe { LLVMRustCreateAllocKindAttr(llcx, kind_arg.bits()) }
}

pub fn CreateRangeAttr(llcx: &Context, size: Size, range: WrappingRange) -> &Attribute {
let lower = range.start;
let upper = range.end.wrapping_add(1);
let lower_words = [lower as u64, (lower >> 64) as u64];
let upper_words = [upper as u64, (upper >> 64) as u64];
unsafe {
LLVMRustCreateRangeAttribute(
llcx,
size.bits().try_into().unwrap(),
lower_words.as_ptr(),
upper_words.as_ptr(),
)
}
}

#[derive(Copy, Clone)]
pub enum AttributePlace {
ReturnValue,
Expand Down
12 changes: 12 additions & 0 deletions compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -397,6 +397,18 @@ LLVMRustCreateAllocSizeAttr(LLVMContextRef C, uint32_t ElementSizeArg) {
std::nullopt));
}

extern "C" LLVMAttributeRef
LLVMRustCreateRangeAttribute(LLVMContextRef C, unsigned NumBits,
const uint64_t LowerWords[],
const uint64_t UpperWords[]) {
#if LLVM_VERSION_GE(19, 0)
return LLVMCreateConstantRangeAttribute(C, Attribute::Range, NumBits,
LowerWords, UpperWords);
#else
report_fatal_error("LLVM 19.0 is required for Range Attribute");
#endif
}

// These values **must** match ffi::AllocKindFlags.
// It _happens_ to match the LLVM values of llvm::AllocFnKind,
// but that's happenstance and we do explicit conversions before
Expand Down
1 change: 1 addition & 0 deletions tests/codegen/call-metadata.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
// scalar value.

//@ compile-flags: -O -C no-prepopulate-passes
//@ ignore-llvm-version: 19 - 99

#![crate_type = "lib"]

Expand Down
2 changes: 0 additions & 2 deletions tests/codegen/cast-optimized.rs
Original file line number Diff line number Diff line change
Expand Up @@ -20,8 +20,6 @@ pub fn u32_index(c: u32) -> [bool; 22] {
// CHECK-LABEL: @char_as_u32_index
#[no_mangle]
pub fn char_as_u32_index(c: char) -> [bool; 22] {
// CHECK: %[[B:.+]] = icmp ult i32 %c, 1114112
// CHECK: call void @llvm.assume(i1 %[[B]])
let c = c as u32;

let mut array = [false; 22];
Expand Down
4 changes: 2 additions & 2 deletions tests/codegen/common_prim_int_ptr.rs
Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,7 @@ pub fn insert_box(x: Box<()>) -> Result<usize, Box<()>> {

// CHECK-LABEL: @extract_int
// CHECK-NOT: nonnull
// CHECK-SAME: (i{{[0-9]+}} {{[^,]+}} [[DISCRIMINANT:%[0-9]+]], ptr {{[^,]+}} [[PAYLOAD:%[0-9]+]])
// CHECK-SAME: (i{{[0-9]+}} {{[^%]+}} [[DISCRIMINANT:%[0-9]+]], ptr {{[^,]+}} [[PAYLOAD:%[0-9]+]])
#[no_mangle]
pub unsafe fn extract_int(x: Result<usize, Box<()>>) -> usize {
// CHECK: [[TEMP:%.+]] = ptrtoint ptr [[PAYLOAD]] to [[USIZE:i[0-9]+]]
Expand All @@ -40,7 +40,7 @@ pub unsafe fn extract_int(x: Result<usize, Box<()>>) -> usize {
}

// CHECK-LABEL: @extract_box
// CHECK-SAME: (i{{[0-9]+}} {{[^,]+}} [[DISCRIMINANT:%[0-9]+]], ptr {{[^,]+}} [[PAYLOAD:%[0-9]+]])
// CHECK-SAME: (i{{[0-9]+}} {{[^%]+}} [[DISCRIMINANT:%[0-9]+]], ptr {{[^,]+}} [[PAYLOAD:%[0-9]+]])
#[no_mangle]
pub unsafe fn extract_box(x: Result<usize, Box<i32>>) -> Box<i32> {
// CHECK: ret ptr [[PAYLOAD]]
Expand Down
2 changes: 1 addition & 1 deletion tests/codegen/enum/enum-match.rs
Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ pub enum Enum1 {

// CHECK: define noundef{{( range\(i8 [0-9]+, [0-9]+\))?}} i8 @match1{{.*}}
// CHECK-NEXT: start:
// CHECK-NEXT: %1 = add i8 %0, -2
// CHECK-NEXT: %1 = add{{( nsw)?}} i8 %0, -2
// CHECK-NEXT: %2 = zext i8 %1 to i64
// CHECK-NEXT: %3 = icmp ult i8 %1, 2
// CHECK-NEXT: %4 = add nuw nsw i64 %2, 1
Expand Down
6 changes: 3 additions & 3 deletions tests/codegen/function-arguments.rs
Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,7 @@ pub fn maybeuninit_enum_bool(x: MaybeUninit<MyBool>) -> MaybeUninit<MyBool> {
x
}

// CHECK: noundef i32 @char(i32 noundef %x)
// CHECK: noundef{{( range\(i32 0, 1114112\))?}} i32 @char(i32 noundef{{( range\(i32 0, 1114112\))?}} %x)
#[no_mangle]
pub fn char(x: char) -> char {
x
Expand All @@ -68,7 +68,7 @@ pub fn int(x: u64) -> u64 {
x
}

// CHECK: noundef i64 @nonzero_int(i64 noundef %x)
// CHECK: noundef{{( range\(i64 1, 0\))?}} i64 @nonzero_int(i64 noundef{{( range\(i64 1, 0\))?}} %x)
#[no_mangle]
pub fn nonzero_int(x: NonZero<u64>) -> NonZero<u64> {
x
Expand Down Expand Up @@ -250,7 +250,7 @@ pub fn return_slice(x: &[u16]) -> &[u16] {
x
}

// CHECK: { i16, i16 } @enum_id_1(i16 noundef %x.0, i16 %x.1)
// CHECK: { i16, i16 } @enum_id_1(i16 noundef{{( range\(i16 0, 3\))?}} %x.0, i16 %x.1)
#[no_mangle]
pub fn enum_id_1(x: Option<Result<u16, u16>>) -> Option<Result<u16, u16>> {
x
Expand Down
2 changes: 1 addition & 1 deletion tests/codegen/issues/issue-68667-unwrap-combinators.rs
Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@
// MIR inlining now optimizes this code.

// CHECK-LABEL: @unwrap_combinators
// CHECK: icmp
// CHECK: {{icmp|trunc}}
// CHECK-NEXT: icmp
// CHECK-NEXT: select i1
// CHECK-NEXT: ret i1
Expand Down
68 changes: 68 additions & 0 deletions tests/codegen/range-attribute.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,68 @@
// Checks that range metadata gets emitted on functions result and arguments
// with scalar value.

//@ compile-flags: -O -C no-prepopulate-passes
//@ min-llvm-version: 19

#![crate_type = "lib"]

use std::num::NonZero;

// CHECK: noundef range(i128 1, 0) i128 @nonzero_int(i128 noundef range(i128 1, 0) %x)
#[no_mangle]
pub fn nonzero_int(x: NonZero<u128>) -> NonZero<u128> {
x
}

// CHECK: noundef range(i8 0, 3) i8 @optional_bool(i8 noundef range(i8 0, 3) %x)
#[no_mangle]
pub fn optional_bool(x: Option<bool>) -> Option<bool> {
x
}

pub enum Enum0 {
A(bool),
B,
C,
}

// CHECK: noundef range(i8 0, 4) i8 @enum0_value(i8 noundef range(i8 0, 4) %x)
#[no_mangle]
pub fn enum0_value(x: Enum0) -> Enum0 {
x
}

pub enum Enum1 {
A(u64),
B(u64),
C(u64),
}

// CHECK: { i64, i64 } @enum1_value(i64 noundef range(i64 0, 3) %x.0, i64 noundef %x.1)
#[no_mangle]
pub fn enum1_value(x: Enum1) -> Enum1 {
x
}

pub enum Enum2 {
A(Enum0),
B(Enum0),
C(Enum0),
}

// CHECK: { i8, i8 } @enum2_value(i8 noundef range(i8 0, 3) %x.0, i8 noundef %x.1)
#[no_mangle]
pub fn enum2_value(x: Enum2) -> Enum2 {
x
}

// Hack to get the correct size for the length part in slices
// CHECK: @helper([[USIZE:i[0-9]+]] noundef %_1)
#[no_mangle]
pub fn helper(_: usize) {}

// CHECK: noundef [[USIZE]] @takes_slice(ptr noalias noundef nonnull readonly align 4 %x.0, [[USIZE]] noundef %x.1)
#[no_mangle]
pub fn takes_slice(x: &[i32]) -> usize {
x.len()
}
2 changes: 1 addition & 1 deletion tests/codegen/repr/transparent.rs
Original file line number Diff line number Diff line change
Expand Up @@ -74,7 +74,7 @@ pub enum Bool {
FileNotFound,
}

// CHECK: define{{( dso_local)?}} noundef{{( zeroext)?}} i8 @test_Gpz(i8 noundef{{( zeroext)?}} %_1)
// CHECK: define{{( dso_local)?}} noundef{{( zeroext)?( range\(i8 0, 3\))?}} i8 @test_Gpz(i8 noundef{{( zeroext)?( range\(i8 0, 3\))?}} %_1)
#[no_mangle]
pub extern "C" fn test_Gpz(_: GenericPlusZst<Bool>) -> GenericPlusZst<Bool> {
loop {}
Expand Down

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