Use the aligned size for alloca at args when the pass mode is cast.

The `load` and `store` instructions in LLVM access the aligned size.

1 files changed, 7 insertions, 1 deletions

diff --git a/compiler/rustc_target/src/abi/call/mod.rs b/compiler/rustc_target/src/abi/call/mod.rs
index 5713542c17d..8058130f441 100644
--- a/compiler/rustc_target/src/abi/call/mod.rs
+++ b/compiler/rustc_target/src/abi/call/mod.rs
@@ -339,7 +339,9 @@ impl CastTarget {
         }
     }
 
-    pub fn size<C: HasDataLayout>(&self, _cx: &C) -> Size {
+    /// When you only access the range containing valid data, you can use this unaligned size;
+    /// otherwise, use the safer `size` method.
+    pub fn unaligned_size<C: HasDataLayout>(&self, _cx: &C) -> Size {
         // Prefix arguments are passed in specific designated registers
         let prefix_size = self
             .prefix
@@ -353,6 +355,10 @@ impl CastTarget {
         prefix_size + rest_size
     }
 
+    pub fn size<C: HasDataLayout>(&self, cx: &C) -> Size {
+        self.unaligned_size(cx).align_to(self.align(cx))
+    }
+
     pub fn align<C: HasDataLayout>(&self, cx: &C) -> Align {
         self.prefix
             .iter()