[PowerPC] Implement builtin for mffsl

mffsl is available since ISA 3.0. The builtin is named with ppc prefix
to follow our convention. For targets earlier than power9, GCC generates
extra code to support the functionality, while this patch does not
implement such behavior.

Reviewed By: nemanjai, tuliom

Differential Revision: https://reviews.llvm.org/D158065

Author: ecnelises

clang/include/clang/Basic/BuiltinsPPC.def

@@ -151,6 +151,7 @@ TARGET_BUILTIN(__builtin_ppc_extract_exp, "Uid", "", "power9-vector")
 TARGET_BUILTIN(__builtin_ppc_extract_sig, "ULLid", "", "power9-vector")
 BUILTIN(__builtin_ppc_mtfsb0, "vUIi", "")
 BUILTIN(__builtin_ppc_mtfsb1, "vUIi", "")
+TARGET_BUILTIN(__builtin_ppc_mffsl, "d", "", "isa-v30-instructions")
 BUILTIN(__builtin_ppc_mtfsf, "vUIiUi", "")
 BUILTIN(__builtin_ppc_mtfsfi, "vUIiUIi", "")
 TARGET_BUILTIN(__builtin_ppc_insert_exp, "ddULLi", "", "power9-vector")

clang/test/CodeGen/PowerPC/builtins-ppc.c

@@ -35,6 +35,11 @@ void test_builtin_ppc_flm() {
 
   // CHECK: call double @llvm.ppc.setflm(double %1)
   res = __builtin_setflm(res);
+
+#ifdef _ARCH_PWR9
+  // P9: call double @llvm.ppc.mffsl()
+  res = __builtin_ppc_mffsl();
+#endif
 }
 
 double test_builtin_unpack_ldbl(long double x) {

llvm/include/llvm/IR/IntrinsicsPowerPC.td

@@ -33,6 +33,10 @@ let TargetPrefix = "ppc" in {  // All intrinsics start with "llvm.ppc.".
   def int_ppc_readflm : ClangBuiltin<"__builtin_readflm">,
                         DefaultAttrsIntrinsic<[llvm_double_ty], [],
                                               [IntrNoMerge, IntrHasSideEffects]>;
+  def int_ppc_mffsl : ClangBuiltin<"__builtin_ppc_mffsl">,
+                      DefaultAttrsIntrinsic<[llvm_double_ty], [],
+                                            [IntrNoMerge, IntrHasSideEffects]>;
+
   // Set FPSCR register, and return previous content
   def int_ppc_setflm : ClangBuiltin<"__builtin_setflm">,
                        DefaultAttrsIntrinsic<[llvm_double_ty], [llvm_double_ty],

llvm/lib/Target/PowerPC/PPCInstrInfo.td

@@ -3180,6 +3180,7 @@ def : Pat<(PPCtc_return CTRRC:$dst, imm:$imm),
           (TCRETURNri CTRRC:$dst, imm:$imm)>;
 
 def : Pat<(int_ppc_readflm), (MFFS)>;
+def : Pat<(int_ppc_mffsl), (MFFSL)>;
 
 // Hi and Lo for Darwin Global Addresses.
 def : Pat<(PPChi tglobaladdr:$in, 0), (LIS tglobaladdr:$in)>;

llvm/test/CodeGen/PowerPC/read-set-flm.ll

@@ -148,8 +148,19 @@ entry:
   ret void
 }
 
+define double @mffsl() {
+; CHECK-LABEL: mffsl:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    mffsl 1
+; CHECK-NEXT:    blr
+entry:
+  %x = call double @llvm.ppc.mffsl()
+  ret double %x
+}
+
 declare void @effect_func()
 declare void @readonly_func() #1
+declare double @llvm.ppc.mffsl()
 declare double @llvm.ppc.readflm()
 declare double @llvm.ppc.setflm(double)
 declare double @llvm.experimental.constrained.fadd.f64(double, double, metadata, metadata)