codegen: on old LLVM, avoid 'inbounds'

Author: RalfJung

compiler/rustc_codegen_llvm/src/builder.rs

@@ -715,15 +715,30 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         ptr: &'ll Value,
         indices: &[&'ll Value],
     ) -> &'ll Value {
-        unsafe {
-            llvm::LLVMBuildInBoundsGEP2(
-                self.llbuilder,
-                ty,
-                ptr,
-                indices.as_ptr(),
-                indices.len() as c_uint,
-                UNNAMED,
-            )
+        let llvm_version = llvm_util::get_version();
+        if llvm_version < (17, 0, 0) {
+            // Old LLVM does not yet have https://reviews.llvm.org/D154051, so we cannot add `inbounds`.
+            unsafe {
+                llvm::LLVMBuildGEP2(
+                    self.llbuilder,
+                    ty,
+                    ptr,
+                    indices.as_ptr(),
+                    indices.len() as c_uint,
+                    UNNAMED,
+                )
+            }
+        } else {
+            unsafe {
+                llvm::LLVMBuildInBoundsGEP2(
+                    self.llbuilder,
+                    ty,
+                    ptr,
+                    indices.as_ptr(),
+                    indices.len() as c_uint,
+                    UNNAMED,
+                )
+            }
         }
     }