[clang] [Clang][AArch64][SVE] Allow write to SVE vector elements using the subscript operator (PR #91965)

[Momchil Velikov via cfe-commits]

https://github.com/momchil-velikov updated https://github.com/llvm/llvm-project/pull/91965

>From 2e081d74e87ad14fdf6d950d3e3da6bed07ee723 Mon Sep 17 00:00:00 2001
From: Momchil Velikov <momchil.velikov at arm.com>
Date: Mon, 13 May 2024 14:27:51 +0100
Subject: [PATCH] [Clang][AArch64][SVE] Allow write to SVE vector elements
 using the subscript operator

The patch at https://reviews.llvm.org/D122732 introduced using
the array subscript operator for SVE vectors, however it also
causes an ICE when the subscripting expression is used
as an lvalue.

This patches fixes the error. Lvalue subscripting expressions are
emitted as LLVM IR `insertvector`.
---
 clang/lib/CodeGen/CGExpr.cpp                          |  6 ++++--
 clang/lib/Sema/SemaExpr.cpp                           |  4 +++-
 clang/test/CodeGen/aarch64-sve-vector-subscript-ops.c | 10 ++++++++++
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index d96c7bb1e5682..37b8b723937b7 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -4180,8 +4180,10 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E,
 
   // If the base is a vector type, then we are forming a vector element lvalue
   // with this subscript.
-  if (E->getBase()->getType()->isVectorType() &&
-      !isa<ExtVectorElementExpr>(E->getBase())) {
+  if (QualType BaseTy = E->getBase()->getType();
+      (BaseTy->isVectorType() && !isa<ExtVectorElementExpr>(E->getBase())) ||
+      (BaseTy->isBuiltinType() &&
+       BaseTy->getAs<BuiltinType>()->isSveVLSBuiltinType())) {
     // Emit the vector as an lvalue to get its address.
     LValue LHS = EmitLValue(E->getBase());
     auto *Idx = EmitIdxAfterBase(/*Promote*/false);
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index bb4b116fd73ca..fd16be30bd848 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -5383,7 +5383,9 @@ Sema::CreateBuiltinArraySubscriptExpr(Expr *Base, SourceLocation LLoc,
   }
 
   // Perform default conversions.
-  if (!LHSExp->getType()->getAs<VectorType>()) {
+  if (!LHSExp->getType()->getAs<VectorType>() &&
+      !(LHSExp->getType()->isBuiltinType() &&
+        LHSExp->getType()->getAs<BuiltinType>()->isSveVLSBuiltinType())) {
     ExprResult Result = DefaultFunctionArrayLvalueConversion(LHSExp);
     if (Result.isInvalid())
       return ExprError();
diff --git a/clang/test/CodeGen/aarch64-sve-vector-subscript-ops.c b/clang/test/CodeGen/aarch64-sve-vector-subscript-ops.c
index fb60c6d100ce6..634423765c4c3 100644
--- a/clang/test/CodeGen/aarch64-sve-vector-subscript-ops.c
+++ b/clang/test/CodeGen/aarch64-sve-vector-subscript-ops.c
@@ -88,3 +88,13 @@ float subscript_float32(svfloat32_t a, size_t b) {
 double subscript_float64(svfloat64_t a, size_t b) {
   return a[b];
 }
+
+// CHECK-LABEL: @subscript_write_float32(
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[VECINS:%.*]] = insertelement <vscale x 4 x float> [[A:%.*]], float 1.000000e+00, i64 [[B:%.*]]
+// CHECK-NEXT:    ret <vscale x 4 x float> [[VECINS]]
+//
+svfloat32_t subscript_write_float32(svfloat32_t a, size_t b) {
+  a[b] = 1.0f;
+  return a;
+}