Add some edge-case tests for emitting the LLVM range attribute

Author: Zalathar

tests/codegen-llvm/range-attr/edge-cases.rs

@@ -0,0 +1,39 @@
+#![feature(rustc_attrs)]
+#![crate_type = "lib"]
+//@ edition: 2024
+
+// Edge-case tests for the conversion from `rustc_abi::WrappingRange` to
+// LLVM range attributes.
+
+#[rustc_layout_scalar_valid_range_start(1)]
+pub struct LowNiche8(u8);
+// CHECK: define void @low_niche_8(i8 noundef range(i8 1, 0) %_1)
+#[unsafe(no_mangle)]
+pub fn low_niche_8(_: LowNiche8) {}
+
+#[rustc_layout_scalar_valid_range_end(254)]
+pub struct HighNiche8(u8);
+// CHECK: define void @high_niche_8(i8 noundef range(i8 0, -1) %_1)
+#[unsafe(no_mangle)]
+pub fn high_niche_8(_: HighNiche8) {}
+
+#[rustc_layout_scalar_valid_range_start(1)]
+#[rustc_layout_scalar_valid_range_end(254)]
+pub struct Niches8(u8);
+// CHECK: define void @niches_8(i8 noundef range(i8 1, -1) %_1)
+#[unsafe(no_mangle)]
+pub fn niches_8(_: Niches8) {}
+
+#[rustc_layout_scalar_valid_range_start(255)]
+#[rustc_layout_scalar_valid_range_end(255)]
+pub struct SoloHigh8(u8);
+// CHECK: define void @solo_high_8(i8 noundef range(i8 -1, 0) %_1)
+#[unsafe(no_mangle)]
+pub fn solo_high_8(_: SoloHigh8) {}
+
+#[rustc_layout_scalar_valid_range_start(1)]
+#[rustc_layout_scalar_valid_range_end(340282366920938463463374607431768211454)] // (u128::MAX - 1)
+pub struct Niches128(u128);
+// CHECK: define void @niches_128(i128 noundef range(i128 1, -1) %_1)
+#[unsafe(no_mangle)]
+pub fn niches_128(_: Niches128) {}