[clang] constexpr built-in elementwise popcount function. (#117473)

Part of #51787.

This patch adds constexpr support for the built-in elementwise popcount
function.

Author: c8ef

clang/docs/LanguageExtensions.rst

@@ -647,6 +647,9 @@ elementwise to the input.
 
 Unless specified otherwise operation(±0) = ±0 and operation(±infinity) = ±infinity
 
+The integer elementwise intrinsics, including ``__builtin_elementwise_popcount``,
+can be called in a ``constexpr`` context.
+
 ============================================== ====================================================================== =========================================
          Name                                   Operation                                                             Supported element types
 ============================================== ====================================================================== =========================================

clang/docs/ReleaseNotes.rst

@@ -375,6 +375,7 @@ Non-comprehensive list of changes in this release
 - ``__builtin_reduce_mul`` function can now be used in constant expressions.
 - ``__builtin_reduce_and`` function can now be used in constant expressions.
 - ``__builtin_reduce_or`` and ``__builtin_reduce_xor`` functions can now be used in constant expressions.
+- ``__builtin_elementwise_popcount`` function can now be used in constant expressions.
 
 New Compiler Flags
 ------------------

clang/include/clang/Basic/Builtins.td

@@ -1354,7 +1354,7 @@ def ElementwiseLog10 : Builtin {
 
 def ElementwisePopcount : Builtin {
   let Spellings = ["__builtin_elementwise_popcount"];
-  let Attributes = [NoThrow, Const, CustomTypeChecking];
+  let Attributes = [NoThrow, Const, CustomTypeChecking, Constexpr];
   let Prototype = "void(...)";
 }
 

clang/lib/AST/ExprConstant.cpp

@@ -11005,6 +11005,7 @@ namespace {
     bool VisitUnaryImag(const UnaryOperator *E);
     bool VisitBinaryOperator(const BinaryOperator *E);
     bool VisitUnaryOperator(const UnaryOperator *E);
+    bool VisitCallExpr(const CallExpr *E);
     bool VisitConvertVectorExpr(const ConvertVectorExpr *E);
     bool VisitShuffleVectorExpr(const ShuffleVectorExpr *E);
 
@@ -11302,6 +11303,35 @@ static bool handleVectorElementCast(EvalInfo &Info, const FPOptions FPO,
   return false;
 }
 
+bool VectorExprEvaluator::VisitCallExpr(const CallExpr *E) {
+  if (!IsConstantEvaluatedBuiltinCall(E))
+    return ExprEvaluatorBaseTy::VisitCallExpr(E);
+
+  switch (E->getBuiltinCallee()) {
+  default:
+    return false;
+  case Builtin::BI__builtin_elementwise_popcount: {
+    APValue Source;
+    if (!EvaluateAsRValue(Info, E->getArg(0), Source))
+      return false;
+
+    QualType DestEltTy = E->getType()->castAs<VectorType>()->getElementType();
+    unsigned SourceLen = Source.getVectorLength();
+    SmallVector<APValue, 4> ResultElements;
+    ResultElements.reserve(SourceLen);
+
+    for (unsigned EltNum = 0; EltNum < SourceLen; ++EltNum) {
+      APSInt Elt = Source.getVectorElt(EltNum).getInt();
+      ResultElements.push_back(
+          APValue(APSInt(APInt(Info.Ctx.getIntWidth(DestEltTy), Elt.popcount()),
+                         DestEltTy->isUnsignedIntegerOrEnumerationType())));
+    }
+
+    return Success(APValue(ResultElements.data(), ResultElements.size()), E);
+  }
+  }
+}
+
 bool VectorExprEvaluator::VisitConvertVectorExpr(const ConvertVectorExpr *E) {
   APValue Source;
   QualType SourceVecType = E->getSrcExpr()->getType();
@@ -13118,6 +13148,7 @@ bool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
   case Builtin::BI__builtin_popcountl:
   case Builtin::BI__builtin_popcountll:
   case Builtin::BI__builtin_popcountg:
+  case Builtin::BI__builtin_elementwise_popcount:
   case Builtin::BI__popcnt16: // Microsoft variants of popcount
   case Builtin::BI__popcnt:
   case Builtin::BI__popcnt64: {

clang/test/CodeGen/builtins-elementwise-math.c

@@ -666,11 +666,9 @@ void test_builtin_elementwise_log2(float f1, float f2, double d1, double d2,
   vf2 = __builtin_elementwise_log2(vf1);
 }
 
-void test_builtin_elementwise_popcount(si8 vi1, si8 vi2,
-                                  long long int i1, long long int i2, short si,
-                                  _BitInt(31) bi1, _BitInt(31) bi2) {
-
-  
+void test_builtin_elementwise_popcount(si8 vi1, si8 vi2, long long int i1,
+                                       long long int i2, short si,
+                                       _BitInt(31) bi1, _BitInt(31) bi2) {
   // CHECK:      [[I1:%.+]] = load i64, ptr %i1.addr, align 8
   // CHECK-NEXT: call i64 @llvm.ctpop.i64(i64 [[I1]])
   i2 = __builtin_elementwise_popcount(i1);
@@ -693,7 +691,7 @@ void test_builtin_elementwise_popcount(si8 vi1, si8 vi2,
   // CHECK-NEXT: call i32 @llvm.ctpop.i32(i32 [[IA1]])
   b = __builtin_elementwise_popcount(int_as_one);
 
-  // CHECK:   call i32 @llvm.ctpop.i32(i32 -10)
+  // CHECK:      store i32 30, ptr @b, align 4
   b = __builtin_elementwise_popcount(-10);
 
   // CHECK:      [[SI:%.+]] = load i16, ptr %si.addr, align 2

clang/test/Sema/constant_builtins_vector.cpp

@@ -797,3 +797,23 @@ static_assert(__builtin_reduce_xor((vector4int){(int)0x11111111, (int)0x22222222
 static_assert(__builtin_reduce_xor((vector4long){(long long)0x1111111111111111L, (long long)0x2222222222222222L, (long long)0x4444444444444444L, (long long)0x8888888888888888L}) == (long long)0xFFFFFFFFFFFFFFFFL);
 static_assert(__builtin_reduce_xor((vector4uint){0x11111111U, 0x22222222U, 0x44444444U, 0x88888888U}) == 0xFFFFFFFFU);
 static_assert(__builtin_reduce_xor((vector4ulong){0x1111111111111111UL, 0x2222222222222222UL, 0x4444444444444444UL, 0x8888888888888888UL}) == 0xFFFFFFFFFFFFFFFFUL);
+
+static_assert(__builtin_bit_cast(unsigned, __builtin_elementwise_popcount((vector4char){1, 2, 3, 4})) == (LITTLE_END ? 0x01020101 : 0x01010201));
+static_assert(__builtin_bit_cast(unsigned long long, __builtin_elementwise_popcount((vector4short){0, 0x0F0F, ~0, ~0x0F0F})) == (LITTLE_END ? 0x0008001000080000 : 0x0000000800100008));
+static_assert(__builtin_reduce_add(__builtin_elementwise_popcount((vector4int){1, 2, 3, 4})) == 5);
+static_assert(__builtin_reduce_add(__builtin_elementwise_popcount((vector4int){0, 0xF0F0, ~0, ~0xF0F0})) == 16 * sizeof(int));
+static_assert(__builtin_reduce_add(__builtin_elementwise_popcount((vector4long){1L, 2L, 3L, 4L})) == 5L);
+static_assert(__builtin_reduce_add(__builtin_elementwise_popcount((vector4long){0L, 0xF0F0L, ~0L, ~0xF0F0L})) == 16 * sizeof(long long));
+static_assert(__builtin_reduce_add(__builtin_elementwise_popcount((vector4uint){1U, 2U, 3U, 4U})) == 5U);
+static_assert(__builtin_reduce_add(__builtin_elementwise_popcount((vector4uint){0U, 0xF0F0U, ~0U, ~0xF0F0U})) == 16 * sizeof(int));
+static_assert(__builtin_reduce_add(__builtin_elementwise_popcount((vector4ulong){1UL, 2UL, 3UL, 4UL})) == 5UL);
+static_assert(__builtin_reduce_add(__builtin_elementwise_popcount((vector4ulong){0ULL, 0xF0F0ULL, ~0ULL, ~0xF0F0ULL})) == 16 * sizeof(unsigned long long));
+static_assert(__builtin_elementwise_popcount(0) == 0);
+static_assert(__builtin_elementwise_popcount(0xF0F0) == 8);
+static_assert(__builtin_elementwise_popcount(~0) == 8 * sizeof(int));
+static_assert(__builtin_elementwise_popcount(0U) == 0);
+static_assert(__builtin_elementwise_popcount(0xF0F0U) == 8);
+static_assert(__builtin_elementwise_popcount(~0U) == 8 * sizeof(int));
+static_assert(__builtin_elementwise_popcount(0L) == 0);
+static_assert(__builtin_elementwise_popcount(0xF0F0L) == 8);
+static_assert(__builtin_elementwise_popcount(~0LL) == 8 * sizeof(long long));