Auto merge of rust-lang#128371 - andjo403:rangeAttribute, r=<try>

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`

Author: bors

compiler/rustc_codegen_llvm/src/abi.rs

@@ -415,9 +415,31 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
             i += 1;
             i - 1
         };
+
+        let apply_range_attr = |idx: AttributePlace, abi: rustc_target::abi::Abi| {
+            if cx.sess().opts.optimize != config::OptLevel::No
+                && llvm_util::get_version() >= (19, 0, 0)
+                && let abi::Abi::Scalar(scalar) = 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(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);
+                apply_range_attr(llvm::AttributePlace::ReturnValue, self.ret.layout.abi);
             }
             PassMode::Indirect { attrs, meta_attrs: _, on_stack } => {
                 assert!(!on_stack);
@@ -456,8 +478,11 @@ 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);
+                    apply_range_attr(llvm::AttributePlace::Argument(i), arg.layout.abi);
+                }
+                PassMode::Indirect { attrs, meta_attrs: None, on_stack: false } => {
                     apply(attrs);
                 }
                 PassMode::Indirect { attrs, meta_attrs: Some(meta_attrs), on_stack } => {
@@ -517,15 +542,18 @@ 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 {

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -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>(

compiler/rustc_codegen_llvm/src/llvm/mod.rs

@@ -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::*;
@@ -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,

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -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

tests/codegen/call-metadata.rs

@@ -2,6 +2,7 @@
 // scalar value.
 
 //@ compile-flags: -O -C no-prepopulate-passes
+//@ ignore-llvm-version: 19 - 99
 
 #![crate_type = "lib"]
 

tests/codegen/enum/enum-match.rs

@@ -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

tests/codegen/function-arguments.rs

@@ -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
@@ -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

tests/codegen/range-attribute.rs

@@ -0,0 +1,33 @@
+// 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]
+fn optional_bool(x: Option<bool>) -> Option<bool> {
+    x
+}
+
+pub enum Enum0 {
+    A(bool),
+    B,
+    C,
+}
+
+// CHECK: noundef range(i8 0, 4) i8 @enum_value(i8 noundef range(i8 0, 4) %x)
+#[no_mangle]
+fn enum_value(x: Enum0) -> Enum0 {
+    x
+}

tests/codegen/repr/transparent.rs

@@ -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 {}