[PATCH] D71133: [OpenCL] Add ExtVectorElementExpr constant evaluation (PR42387)

[Sven van Haastregt via Phabricator via cfe-commits]

svenvh created this revision.
svenvh added a reviewer: Anastasia.
Herald added a subscriber: yaxunl.

Add constexpr evaluation for ExtVectorElementExpr nodes by evaluating
the underlying vector expression.

Add basic folding too, for the case that Evaluate does not return an
LValue.


https://reviews.llvm.org/D71133

Files:
  clang/lib/AST/ExprConstant.cpp
  clang/test/CodeGenOpenCLCXX/constexpr.cl


Index: clang/test/CodeGenOpenCLCXX/constexpr.cl
===================================================================
--- clang/test/CodeGenOpenCLCXX/constexpr.cl
+++ clang/test/CodeGenOpenCLCXX/constexpr.cl
@@ -1,5 +1,8 @@
 // RUN: %clang_cc1 %s -triple spir-unknown-unknown -cl-std=clc++ -O0 -emit-llvm -o - | FileCheck %s
 
+typedef int int2 __attribute__((ext_vector_type(2)));
+typedef int int4 __attribute__((ext_vector_type(4)));
+
 struct Storage final {
   constexpr const float& operator[](const int index) const noexcept {
     return InternalStorage[index];
@@ -24,3 +27,28 @@
 kernel void foo(global float *x) {
   *x = FloatConstant;
 }
+
+// Test evaluation of constant vectors.
+// CHECK-LABEL: define spir_kernel void @vecEval
+// CHECK: store i32 3
+// CHECK: store <2 x i32> <i32 22, i32 33>, <2 x i32>
+
+const int oneElt = int4(3).x;
+const int2 twoElts = (int4)(11, 22, 33, 44).yz;
+
+kernel void vecEval(global int *x, global int2 *y) {
+  *x = oneElt;
+  *y = twoElts;
+}
+
+// Test evaluation of vectors initialized through a constexpr function.
+// CHECK-LABEL: define spir_kernel void @vecEval2
+// CHECK: store <2 x i32>
+constexpr int2 addOne(int2 x) {
+  return (int2)(x.x + 1, x.y + 1);
+}
+const int2 fromConstexprFunc = addOne(int2(2));
+
+kernel void vecEval2(global int2 *x) {
+  *x = fromConstexprFunc;
+}
Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -7049,6 +7049,31 @@
            DerivedSuccess(Result, E);
   }
 
+  bool VisitExtVectorElementExpr(const ExtVectorElementExpr *E) {
+    APValue Val;
+    if (!Evaluate(Val, Info, E->getBase()))
+      return false;
+
+    if (Val.isVector()) {
+      SmallVector<uint32_t, 4> Indices;
+      E->getEncodedElementAccess(Indices);
+      if (Indices.size() == 1) {
+        // Return scalar.
+        return DerivedSuccess(Val.getVectorElt(Indices[0]), E);
+      } else {
+        // Construct new APValue vector.
+        SmallVector<APValue, 4> Elts;
+        for (unsigned I = 0; I < Indices.size(); ++I) {
+          Elts.push_back(Val.getVectorElt(Indices[I]));
+        }
+        APValue VecResult(Elts.data(), Indices.size());
+        return DerivedSuccess(VecResult, E);
+      }
+    }
+
+    return false;
+  }
+
   bool VisitCastExpr(const CastExpr *E) {
     switch (E->getCastKind()) {
     default:


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