[PowerPC] Add the support for __builtin_setrnd() in clang

[ZhangKang]

Summary

PowerPC64/PowerPC64le supports the builtin function __builtin_setrnd to set the floating point rounding mode. This function will use the least significant two bits of integer argument to set the floating point rounding mode.

double __builtin_setrnd(int mode);

The effective values for mode are:

0 - round to nearest
1 - round to zero
2 - round to +infinity
3 - round to -infinity

Note that the mode argument will modulo 4, so if the int argument is greater than 3, it will only use the least significant two bits of the mode. Namely, builtin_setrnd(102)) is equal to builtin_setrnd(2).

[jsji]

Apparently missing some files.

[jsji]

In D59403#1430383, @jsji wrote:

Apparently missing some files.

OK, added dependent revision https://reviews.llvm.org/D59405.

[ZhangKang]

Have checked the missing files.

[ZhangKang]

Update the patch.

[jsji]

LGTM.

[jsji]

Looks like you did not commit the version (Diff 190782) that was accepted!

So introduced duplicate documents in commits (Diff 192788) .
Thanks @davezarzycki for noticing this and fix it in https://reviews.llvm.org/rL369496.

@ZhangKang Please pay more attention next time. Thanks.

[ZhangKang]

In D59403#1639298, @jsji wrote:

Looks like you did not commit the version (Diff 190782) that was accepted!

So introduced duplicate documents in commits (Diff 192788) .
Thanks @davezarzycki for noticing this and fix it in https://reviews.llvm.org/rL369496.

@ZhangKang Please pay more attention next time. Thanks.

I am sorry for it. I will be careful next time.

clang/docs/LanguageExtensions.rst

 
 .. code-block:: gas
 
   _foo:
           movl    4(%esp), %eax
           movl    %gs:(%eax), %eax
           ret
 
+PowerPC Language Extensions
+------------------------------
+
+Set the Floating Point Rounding Mode
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+PowerPC64/PowerPC64le supports the builtin function ``__builtin_setrnd`` to set
+the floating point rounding mode. This function will use the least significant
+two bits of integer argument to set the floating point rounding mode.
+
+.. code-block:: c++
+
+  double __builtin_setrnd(int mode);
+
+The effective values for mode are:
+
+    - 0 - round to nearest
+    - 1 - round to zero
+    - 2 - round to +infinity
+    - 3 - round to -infinity
+
+Note that the mode argument will modulo 4, so if the integer argument is greater
+than 3, it will only use the least significant two bits of the mode. 
+Namely, ``__builtin_setrnd(102))`` is equal to ``__builtin_setrnd(2)``.
+
 Extensions for Static Analysis
 ==============================
 
 Clang supports additional attributes that are useful for documenting program
 invariants and rules for static analysis tools, such as the `Clang Static
 Analyzer <https://clang-analyzer.llvm.org/>`_. These attributes are documented
 in the analyzer's `list of source-level annotations
 <https://clang-analyzer.llvm.org/annotations.html>`_.

clang/include/clang/Basic/BuiltinsPPC.def

 BUILTIN(__builtin_divde, "SLLiSLLiSLLi", "")
 BUILTIN(__builtin_divdeu, "ULLiULLiULLi", "")
 BUILTIN(__builtin_bpermd, "SLLiSLLiSLLi", "")
 
 // Vector int128 (un)pack
 BUILTIN(__builtin_unpack_vector_int128, "ULLiV1LLLii", "")
 BUILTIN(__builtin_pack_vector_int128, "V1LLLiULLiULLi", "")
 
+// Set the floating point rounding mode
+BUILTIN(__builtin_setrnd, "di", "")
+
 // FIXME: Obviously incomplete.
 
 #undef BUILTIN

clang/test/CodeGen/builtins-ppc.c

 // REQUIRES: powerpc-registered-target
 // RUN: %clang_cc1 -triple powerpc-unknown-unknown -emit-llvm %s -o - | FileCheck %s
 
 void test_eh_return_data_regno()
 {
   volatile int res;
   res = __builtin_eh_return_data_regno(0);  // CHECK: store volatile i32 3
   res = __builtin_eh_return_data_regno(1);  // CHECK: store volatile i32 4
 }
 
 // CHECK-LABEL: define i64 @test_builtin_ppc_get_timebase
 long long test_builtin_ppc_get_timebase() {
   // CHECK: call i64 @llvm.readcyclecounter()
   return __builtin_ppc_get_timebase();
 }
 
+void test_builtin_ppc_setrnd() {
+  volatile double res;
+  volatile int x = 100;
+  
+  // CHECK: call double @llvm.ppc.setrnd(i32 2)
+  res = __builtin_setrnd(2);
+
+  // CHECK: call double @llvm.ppc.setrnd(i32 100)
+  res = __builtin_setrnd(100);
+
+  // CHECK: call double @llvm.ppc.setrnd(i32 %2)
+  res = __builtin_setrnd(x);
+}