[clang][AArch64] Fix C++11 style initialization of typedef'd vectors

Previously, this hit an `llvm_unreachable()` assertion as the type of
`vec_t` did not exactly match the return type of `svdup_s8`, as it was
wrapped in a typedef.

Comparing the canonical types instead allows the types to match
correctly and avoids the crash.

Fixes #107609

Author: MacDue

clang/lib/CodeGen/CGExprScalar.cpp

@@ -2102,7 +2102,8 @@ Value *ScalarExprEmitter::VisitInitListExpr(InitListExpr *E) {
       Expr *InitVector = E->getInit(0);
 
       // Initialize from another scalable vector of the same type.
-      if (InitVector->getType() == E->getType())
+      if (InitVector->getType().getCanonicalType() ==
+          E->getType().getCanonicalType())
         return Visit(InitVector);
     }
 

clang/test/CodeGenCXX/aarch64-sve-vector-init-typedef.cpp

@@ -0,0 +1,23 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 2
+// RUN: %clang_cc1 -fclang-abi-compat=latest -triple aarch64-none-linux-gnu -target-feature +sve -emit-llvm -o - %s | FileCheck %s
+
+#include <arm_sve.h>
+
+using vec_t = svint8_t;
+
+/// From: https://github.com/llvm/llvm-project/issues/107609
+/// The type of `vec` is a typedef of svint8_t, while svdup_s8 returns the non-typedef'd type.
+
+// CHECK-LABEL: define dso_local <vscale x 16 x i8> @_Z20sve_init_dup_typedefv
+// CHECK-SAME: () #[[ATTR0:[0-9]+]] {
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[VEC:%.*]] = alloca <vscale x 16 x i8>, align 16
+// CHECK-NEXT:    [[TMP0:%.*]] = call <vscale x 16 x i8> @llvm.aarch64.sve.dup.x.nxv16i8(i8 2)
+// CHECK-NEXT:    store <vscale x 16 x i8> [[TMP0]], ptr [[VEC]], align 16
+// CHECK-NEXT:    [[TMP1:%.*]] = load <vscale x 16 x i8>, ptr [[VEC]], align 16
+// CHECK-NEXT:    ret <vscale x 16 x i8> [[TMP1]]
+//
+vec_t sve_init_dup_typedef() {
+  vec_t vec{svdup_s8(2)};
+  return vec;
+}