commit 5cf58768cb3ba31ee37facaf23f7a74f78781590
author Tim Northover <t.p.northover@gmail.com> Thu Nov 21 10:31:30 2019 +0000
committer Tim Northover <t.p.northover@gmail.com> Thu Nov 21 10:37:56 2019 +0000
tree 7b811554233ff808a360120b3404987354c4e54b
parent 9f3fdb0d7fab73083e354768eb5808597474e1b8

Atomics: support min/max orthogonally

We seem to have been gradually growing support for atomic min/max operations
(exposing longstanding IR atomicrmw instructions). But until now there have
been gaps in the expected intrinsics. This adds support for the C11-style
intrinsics (i.e. taking _Atomic, rather than individually blessed by C11
standard), and the variants that return the new value instead of the original
one.

That way, people won't be misled by trying one form and it not working, and the
front-end is more friendly to people using _Atomic types, as we recommend.

clang/lib/Sema/SemaChecking.cpp

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index a4218ad..c19badf 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -4572,20 +4572,19 @@
       && sizeof(NumVals)/sizeof(NumVals[0]) == NumForm,
       "need to update code for modified forms");
   static_assert(AtomicExpr::AO__c11_atomic_init == 0 &&
-                    AtomicExpr::AO__c11_atomic_fetch_xor + 1 ==
+                    AtomicExpr::AO__c11_atomic_fetch_min + 1 ==
                         AtomicExpr::AO__atomic_load,
                 "need to update code for modified C11 atomics");
   bool IsOpenCL = Op >= AtomicExpr::AO__opencl_atomic_init &&
                   Op <= AtomicExpr::AO__opencl_atomic_fetch_max;
   bool IsC11 = (Op >= AtomicExpr::AO__c11_atomic_init &&
-               Op <= AtomicExpr::AO__c11_atomic_fetch_xor) ||
+               Op <= AtomicExpr::AO__c11_atomic_fetch_min) ||
                IsOpenCL;
   bool IsN = Op == AtomicExpr::AO__atomic_load_n ||
              Op == AtomicExpr::AO__atomic_store_n ||
              Op == AtomicExpr::AO__atomic_exchange_n ||
              Op == AtomicExpr::AO__atomic_compare_exchange_n;
   bool IsAddSub = false;
-  bool IsMinMax = false;
 
   switch (Op) {
   case AtomicExpr::AO__c11_atomic_init:
@@ -4636,12 +4635,12 @@
   case AtomicExpr::AO__atomic_or_fetch:
   case AtomicExpr::AO__atomic_xor_fetch:
   case AtomicExpr::AO__atomic_nand_fetch:
-    Form = Arithmetic;
-    break;
-
+  case AtomicExpr::AO__c11_atomic_fetch_min:
+  case AtomicExpr::AO__c11_atomic_fetch_max:
+  case AtomicExpr::AO__atomic_min_fetch:
+  case AtomicExpr::AO__atomic_max_fetch:
   case AtomicExpr::AO__atomic_fetch_min:
   case AtomicExpr::AO__atomic_fetch_max:
-    IsMinMax = true;
     Form = Arithmetic;
     break;
 
@@ -4733,16 +4732,8 @@
           << IsC11 << Ptr->getType() << Ptr->getSourceRange();
       return ExprError();
     }
-    if (IsMinMax) {
-      const BuiltinType *BT = ValType->getAs<BuiltinType>();
-      if (!BT || (BT->getKind() != BuiltinType::Int &&
-                  BT->getKind() != BuiltinType::UInt)) {
-        Diag(ExprRange.getBegin(), diag::err_atomic_op_needs_int32_or_ptr);
-        return ExprError();
-      }
-    }
-    if (!IsAddSub && !IsMinMax && !ValType->isIntegerType()) {
-      Diag(ExprRange.getBegin(), diag::err_atomic_op_bitwise_needs_atomic_int)
+    if (!IsAddSub && !ValType->isIntegerType()) {
+      Diag(ExprRange.getBegin(), diag::err_atomic_op_needs_atomic_int)
           << IsC11 << Ptr->getType() << Ptr->getSourceRange();
       return ExprError();
     }