[ARM] Promote fp16 frem

[dmgreen]

Summary

Promote fp16 frem operations on ARM so they call fmodf. Otherwise we fail to select them.

Test is new and not in-tree yet.

[SjoerdMeijer]

LGTM

llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp

if (!Subtarget->isFPOnlySP()) {
       setOperationAction(ISD::FTRUNC, MVT::f64, Legal);
       setOperationAction(ISD::FNEARBYINT, MVT::f64, Legal);
       setOperationAction(ISD::FRINT, MVT::f64, Legal);
       setOperationAction(ISD::FMINNUM, MVT::f64, Legal);
       setOperationAction(ISD::FMAXNUM, MVT::f64, Legal);
     }
   }
 
+  // FP16 often need to be promoted to call lib functions
+  if (Subtarget->hasFullFP16()) {
+    setOperationAction(ISD::FREM, MVT::f16, Promote);
+  }
+
   if (Subtarget->hasNEON()) {
     // vmin and vmax aren't available in a scalar form, so we use
     // a NEON instruction with an undef lane instead.
     setOperationAction(ISD::FMINIMUM, MVT::f16, Legal);
     setOperationAction(ISD::FMAXIMUM, MVT::f16, Legal);
     setOperationAction(ISD::FMINIMUM, MVT::f32, Legal);
     setOperationAction(ISD::FMAXIMUM, MVT::f32, Legal);
     setOperationAction(ISD::FMINIMUM, MVT::v2f32, Legal);

llvm/trunk/test/CodeGen/ARM/fp16-fullfp16.ll

 ; CHECK-NEXT:    bx lr
   %a = load half, half* %p, align 2
   %b = load half, half* %q, align 2
   %r = fdiv half %a, %b
   store half %r, half* %p
   ret void
 }
 
-; FIXME
-;define void @test_frem(half* %p, half* %q) {
-;  %a = load half, half* %p, align 2
-;  %b = load half, half* %q, align 2
-;  %r = frem half %a, %b
-;  store half %r, half* %p
-;  ret void
-;}
+define arm_aapcs_vfpcc void @test_frem(half* %p, half* %q) {
+; CHECK-LABEL: test_frem:
+; CHECK:         .save {r4, lr}
+; CHECK-NEXT:    push {r4, lr}
+; CHECK-NEXT:    vldr.16 s2, [r1]
+; CHECK-NEXT:    vldr.16 s0, [r0]
+; CHECK-NEXT:    mov r4, r0
+; CHECK-NEXT:    vcvtb.f32.f16 s0, s0
+; CHECK-NEXT:    vcvtb.f32.f16 s1, s2
+; CHECK-NEXT:    bl fmodf
+; CHECK-NEXT:    vcvtb.f16.f32 s0, s0
+; CHECK-NEXT:    vstr.16 s0, [r4]
+; CHECK-NEXT:    pop {r4, pc}
+  %a = load half, half* %p, align 2
+  %b = load half, half* %q, align 2
+  %r = frem half %a, %b
+  store half %r, half* %p
+  ret void
+}
 
 define void @test_load_store(half* %p, half* %q) {
 ; CHECK-LABEL: test_load_store:
 ; CHECK:         vldr.16 s0, [r0]
 ; CHECK-NEXT:    vstr.16 s0, [r1]
 ; CHECK-NEXT:    bx lr
   %a = load half, half* %p, align 2
   store half %a, half* %q