From 3fc506b4d43938453fd399f403507e4b2031a167 Mon Sep 17 00:00:00 2001
From: DianQK <dianqk@dianqk.net>
Date: Sun, 15 Dec 2024 19:01:24 +0800
Subject: [PATCH] Simplify the GEP instruction for index

---
 compiler/rustc_codegen_ssa/src/mir/place.rs   |  5 +--
 .../bounds-checking/gep-issue-133979.rs       | 22 +++++++++++
 tests/codegen/gep-index.rs                    | 37 +++++++++++++++++++
 3 files changed, 60 insertions(+), 4 deletions(-)
 create mode 100644 tests/codegen/bounds-checking/gep-issue-133979.rs
 create mode 100644 tests/codegen/gep-index.rs

diff --git a/compiler/rustc_codegen_ssa/src/mir/place.rs b/compiler/rustc_codegen_ssa/src/mir/place.rs
index c38484109d2..a9e80e27ed4 100644
--- a/compiler/rustc_codegen_ssa/src/mir/place.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/place.rs
@@ -422,10 +422,7 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
             layout.size
         };
 
-        let llval = bx.inbounds_gep(bx.cx().backend_type(self.layout), self.val.llval, &[
-            bx.cx().const_usize(0),
-            llindex,
-        ]);
+        let llval = bx.inbounds_gep(bx.cx().backend_type(layout), self.val.llval, &[llindex]);
         let align = self.val.align.restrict_for_offset(offset);
         PlaceValue::new_sized(llval, align).with_type(layout)
     }
diff --git a/tests/codegen/bounds-checking/gep-issue-133979.rs b/tests/codegen/bounds-checking/gep-issue-133979.rs
new file mode 100644
index 00000000000..876bdbfb0e1
--- /dev/null
+++ b/tests/codegen/bounds-checking/gep-issue-133979.rs
@@ -0,0 +1,22 @@
+//! Issue: <https://github.com/rust-lang/rust/issues/133979>
+//! Check that bounds checking are eliminated.
+
+//@ compile-flags: -Copt-level=2
+
+#![crate_type = "lib"]
+
+// CHECK-LABEL: @test(
+#[no_mangle]
+fn test(a: &[&[u8]]) -> u32 {
+    // CHECK-NOT: panic_bounds_check
+    a.iter()
+        .enumerate()
+        .map(|(y, b)| {
+            b.iter()
+                .enumerate()
+                .filter(|(_, c)| **c == b'A')
+                .map(|(x, _)| a[y][x] as u32)
+                .sum::<u32>()
+        })
+        .sum()
+}
diff --git a/tests/codegen/gep-index.rs b/tests/codegen/gep-index.rs
new file mode 100644
index 00000000000..1f5e8855910
--- /dev/null
+++ b/tests/codegen/gep-index.rs
@@ -0,0 +1,37 @@
+//! Check that index and offset use the same getelementptr format.
+
+//@ revisions: NO-OPT OPT
+//@[NO-OPT] compile-flags: -Copt-level=0
+//@[OPT] compile-flags: -Copt-level=1
+
+#![crate_type = "lib"]
+
+struct Foo(i32, i32);
+
+// CHECK-LABEL: @index_on_struct(
+#[no_mangle]
+fn index_on_struct(a: &[Foo], index: usize) -> &Foo {
+    // CHECK: getelementptr inbounds %Foo, ptr %a.0, {{i64|i32}} %index
+    &a[index]
+}
+
+// CHECK-LABEL: @offset_on_struct(
+#[no_mangle]
+fn offset_on_struct(a: *const Foo, index: usize) -> *const Foo {
+    // CHECK: getelementptr inbounds %Foo, ptr %a, {{i64|i32}} %index
+    unsafe { a.add(index) }
+}
+
+// CHECK-LABEL: @index_on_i32(
+#[no_mangle]
+fn index_on_i32(a: &[i32], index: usize) -> &i32 {
+    // CHECK: getelementptr inbounds i32, ptr %a.0, {{i64|i32}} %index
+    &a[index]
+}
+
+// CHECK-LABEL: @offset_on_i32(
+#[no_mangle]
+fn offset_on_i32(a: *const i32, index: usize) -> *const i32 {
+    // CHECK: getelementptr inbounds i32, ptr %a, {{i64|i32}} %index
+    unsafe { a.add(index) }
+}