[clang] [clang] constexpr built-in elementwise add_sat function. (PR #119082)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: None (c8ef)

<details>
<summary>Changes</summary>

Part of #<!-- -->51787.

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

---
Full diff: https://github.com/llvm/llvm-project/pull/119082.diff


6 Files Affected:

- (modified) clang/docs/LanguageExtensions.rst (+2-1) 
- (modified) clang/docs/ReleaseNotes.rst (+1) 
- (modified) clang/include/clang/Basic/Builtins.td (+1-1) 
- (modified) clang/lib/AST/ExprConstant.cpp (+35) 
- (modified) clang/test/CodeGen/builtins-elementwise-math.c (+1-1) 
- (modified) clang/test/Sema/constant_builtins_vector.cpp (+8) 


``````````diff
diff --git a/clang/docs/LanguageExtensions.rst b/clang/docs/LanguageExtensions.rst
index 6b950d05fb9bf9..40c0a0e5f1161c 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -648,7 +648,8 @@ elementwise to the input.
 Unless specified otherwise operation(±0) = ±0 and operation(±infinity) = ±infinity
 
 The integer elementwise intrinsics, including ``__builtin_elementwise_popcount``,
-``__builtin_elementwise_bitreverse``, can be called in a ``constexpr`` context.
+``__builtin_elementwise_bitreverse``, ``__builtin_elementwise_add_sat``, can be
+called in a ``constexpr`` context.
 
 ============================================== ====================================================================== =========================================
          Name                                   Operation                                                             Supported element types
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 59e3a6609123d2..5aeda3ade7573a 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -414,6 +414,7 @@ Non-comprehensive list of changes in this release
 - ``__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.
 - ``__builtin_elementwise_bitreverse`` function can now be used in constant expressions.
+- ``__builtin_elementwise_add_sat`` function can now be used in constant expressions.
 
 New Compiler Flags
 ------------------
diff --git a/clang/include/clang/Basic/Builtins.td b/clang/include/clang/Basic/Builtins.td
index e2c3d3c535571c..1186ece419fdd2 100644
--- a/clang/include/clang/Basic/Builtins.td
+++ b/clang/include/clang/Basic/Builtins.td
@@ -1450,7 +1450,7 @@ def ElementwiseFma : Builtin {
 
 def ElementwiseAddSat : Builtin {
   let Spellings = ["__builtin_elementwise_add_sat"];
-  let Attributes = [NoThrow, Const, CustomTypeChecking];
+  let Attributes = [NoThrow, Const, CustomTypeChecking, Constexpr];
   let Prototype = "void(...)";
 }
 
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 6b5b95aee35522..001773dc28dedc 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -11339,6 +11339,31 @@ bool VectorExprEvaluator::VisitCallExpr(const CallExpr *E) {
 
     return Success(APValue(ResultElements.data(), ResultElements.size()), E);
   }
+  case Builtin::BI__builtin_elementwise_add_sat: {
+    APValue SourceLHS, SourceRHS;
+    if (!EvaluateAsRValue(Info, E->getArg(0), SourceLHS) ||
+        !EvaluateAsRValue(Info, E->getArg(1), SourceRHS))
+      return false;
+
+    QualType DestEltTy = E->getType()->castAs<VectorType>()->getElementType();
+    unsigned SourceLen = SourceLHS.getVectorLength();
+    SmallVector<APValue, 4> ResultElements;
+    ResultElements.reserve(SourceLen);
+
+    for (unsigned EltNum = 0; EltNum < SourceLen; ++EltNum) {
+      APSInt LHS = SourceLHS.getVectorElt(EltNum).getInt();
+      APSInt RHS = SourceRHS.getVectorElt(EltNum).getInt();
+      switch (E->getBuiltinCallee()) {
+      case Builtin::BI__builtin_elementwise_add_sat:
+        ResultElements.push_back(APValue(
+            APSInt(LHS.isSigned() ? LHS.sadd_sat(RHS) : RHS.uadd_sat(RHS),
+                   DestEltTy->isUnsignedIntegerOrEnumerationType())));
+        break;
+      }
+    }
+
+    return Success(APValue(ResultElements.data(), ResultElements.size()), E);
+  }
   }
 }
 
@@ -13204,6 +13229,16 @@ bool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
     return Success(Val.rotr(Amt.urem(Val.getBitWidth())), E);
   }
 
+  case Builtin::BI__builtin_elementwise_add_sat: {
+    APSInt LHS, RHS;
+    if (!EvaluateInteger(E->getArg(0), LHS, Info) ||
+        !EvaluateInteger(E->getArg(1), RHS, Info))
+      return false;
+
+    APInt Result = LHS.isSigned() ? LHS.sadd_sat(RHS) : LHS.uadd_sat(RHS);
+    return Success(APSInt(Result, !LHS.isSigned()), E);
+  }
+
   case Builtin::BIstrlen:
   case Builtin::BIwcslen:
     // A call to strlen is not a constant expression.
diff --git a/clang/test/CodeGen/builtins-elementwise-math.c b/clang/test/CodeGen/builtins-elementwise-math.c
index 82f82dd1ed7944..832691a55e52a1 100644
--- a/clang/test/CodeGen/builtins-elementwise-math.c
+++ b/clang/test/CodeGen/builtins-elementwise-math.c
@@ -112,7 +112,7 @@ void test_builtin_elementwise_add_sat(float f1, float f2, double d1, double d2,
   // CHECK-NEXT: call i32 @llvm.sadd.sat.i32(i32 [[IAS1]], i32 [[B]])
   int_as_one = __builtin_elementwise_add_sat(int_as_one, b);
 
-  // CHECK: call i32 @llvm.sadd.sat.i32(i32 1, i32 97)
+  // CHECK: store i64 98, ptr %i1.addr, align 8
   i1 = __builtin_elementwise_add_sat(1, 'a');
 }
 
diff --git a/clang/test/Sema/constant_builtins_vector.cpp b/clang/test/Sema/constant_builtins_vector.cpp
index 45c729f76418d1..b23889e3c82828 100644
--- a/clang/test/Sema/constant_builtins_vector.cpp
+++ b/clang/test/Sema/constant_builtins_vector.cpp
@@ -822,3 +822,11 @@ static_assert(__builtin_elementwise_bitreverse(0x12345678) == 0x1E6A2C48);
 static_assert(__builtin_elementwise_bitreverse(0x0123456789ABCDEFULL) == 0xF7B3D591E6A2C480);
 static_assert(__builtin_bit_cast(unsigned, __builtin_elementwise_bitreverse((vector4char){1, 2, 4, 8})) == (LITTLE_END ? 0x10204080 : 0x80402010));
 static_assert(__builtin_bit_cast(unsigned long long, __builtin_elementwise_bitreverse((vector4short){1, 2, 4, 8})) == (LITTLE_END ? 0x1000200040008000 : 0x8000400020001000));
+
+static_assert(__builtin_elementwise_add_sat(1, 2) == 3);
+static_assert(__builtin_elementwise_add_sat(1U, 2U) == 3U);
+static_assert(__builtin_elementwise_add_sat(~(1 << 31), 42) == ~(1 << 31));
+static_assert(__builtin_elementwise_add_sat((1 << 31), -42) == (1 << 31));
+static_assert(__builtin_elementwise_add_sat(~0U, 1U) == ~0U);
+static_assert(__builtin_bit_cast(unsigned, __builtin_elementwise_add_sat((vector4char){1, 2, 3, 4}, (vector4char){4, 3, 2, 1})) == (LITTLE_END ? 0x05050505 : 0x05050505));
+static_assert(__builtin_bit_cast(unsigned long long, __builtin_elementwise_add_sat((vector4short){(short)0x8000, (short)0x8001, (short)0x8002, (short)0x8003}, (vector4short){-7, -8, -9, -10}) == (LITTLE_END ? 0x8000800080008000 : 0x8000800080008000)));

``````````

</details>


https://github.com/llvm/llvm-project/pull/119082