Auto merge of rust-lang#134117 - DianQK:gep-i8, r=<try>

[WIP] Canonicalize GEPs Fixes rust-lang#133979. r? ghost
rust-lang-ci · Dec 10, 2024 · 945e153 · 945e153
2 parents b597d2a + 23cc55f
commit 945e153
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Showing 2 changed files with 21 additions and 6 deletions.
diff --git a/compiler/rustc_codegen_ssa/src/mir/place.rs b/compiler/rustc_codegen_ssa/src/mir/place.rs
@@ -422,10 +422,18 @@ 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 = {
+            let pointee_layout = layout;
+            let bytes = pointee_layout.size.align_to(pointee_layout.align.abi).bytes();
+            let rhs = if bytes == 1 {
+                llindex
+            } else {
+                let lhs = llindex;
+                let rhs = bx.cx().const_usize(bytes);
+                bx.unchecked_umul(lhs, rhs)
+            };
+            bx.inbounds_ptradd(self.val.llval, rhs)
+        };
         let align = self.val.align.restrict_for_offset(offset);
         PlaceValue::new_sized(llval, align).with_type(layout)
     }

diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -925,8 +925,15 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     // so offsetting a pointer to ZST is a noop.
                     lhs
                 } else {
-                    let llty = bx.cx().backend_type(pointee_layout);
-                    bx.inbounds_gep(llty, lhs, &[rhs])
+                    let bytes = pointee_layout.size.align_to(pointee_layout.align.abi).bytes();
+                    let rhs = if bytes == 1 {
+                        rhs
+                    } else {
+                        let lhs = rhs;
+                        let rhs = bx.cx().const_usize(bytes);
+                        bx.unchecked_umul(lhs, rhs)
+                    };
+                    bx.inbounds_ptradd(lhs, rhs)
                 }
             }
             mir::BinOp::Shl | mir::BinOp::ShlUnchecked => {