From d180f918240d2f8bd3d6f7292b63194f45901759 Mon Sep 17 00:00:00 2001
From: hi-rustin <rustin.liu@gmail.com>
Date: Thu, 11 Mar 2021 23:30:39 +0800
Subject: [PATCH] Emit the enum range assumption if the range only contains one
 element

test: add test case

make tidy happy
---
 compiler/rustc_codegen_ssa/src/mir/rvalue.rs     |  2 +-
 .../codegen/enum-bounds-check-issue-82871.rs     | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)
 create mode 100644 src/test/codegen/enum-bounds-check-issue-82871.rs

diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
index 1795710ff53..629cb64d43e 100644
--- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -325,7 +325,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
                                 let er = scalar.valid_range_exclusive(bx.cx());
                                 if er.end != er.start
-                                    && scalar.valid_range.end() > scalar.valid_range.start()
+                                    && scalar.valid_range.end() >= scalar.valid_range.start()
                                 {
                                     // We want `table[e as usize ± k]` to not
                                     // have bound checks, and this is the most
diff --git a/src/test/codegen/enum-bounds-check-issue-82871.rs b/src/test/codegen/enum-bounds-check-issue-82871.rs
new file mode 100644
index 00000000000..e779e2ef274
--- /dev/null
+++ b/src/test/codegen/enum-bounds-check-issue-82871.rs
@@ -0,0 +1,16 @@
+// compile-flags: -O
+// min-llvm-version: 11.0
+
+#![crate_type = "lib"]
+
+#[repr(C)]
+pub enum E {
+    A,
+}
+
+// CHECK-LABEL: @index
+#[no_mangle]
+pub fn index(x: &[u32; 3], ind: E) -> u32{
+    // CHECK-NOT: panic_bounds_check
+    x[ind as usize]
+}