[PowerPC] Only legalize FNEARBYINT with unsafe fp math

Commit 0f0330a legalized these nodes on PPC without consideration of
unsafe math which means that we get inexact exceptions raised for nearbyint.
Since this doesn't conform to the standard, switch this legalization to depend
on unsafe fp math.

Author: nemanjai

llvm/lib/Target/PowerPC/PPCISelLowering.cpp

@@ -782,17 +782,22 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM,
       }
       setOperationAction(ISD::EXTRACT_VECTOR_ELT, MVT::v2f64, Legal);
 
+      // The nearbyint variants are not allowed to raise the inexact exception
+      // so we can only code-gen them with unsafe math.
+      if (TM.Options.UnsafeFPMath) {
+        setOperationAction(ISD::FNEARBYINT, MVT::f64, Legal);
+        setOperationAction(ISD::FNEARBYINT, MVT::f32, Legal);
+      }
+
       setOperationAction(ISD::FFLOOR, MVT::v2f64, Legal);
       setOperationAction(ISD::FCEIL, MVT::v2f64, Legal);
       setOperationAction(ISD::FTRUNC, MVT::v2f64, Legal);
       setOperationAction(ISD::FNEARBYINT, MVT::v2f64, Legal);
       setOperationAction(ISD::FROUND, MVT::v2f64, Legal);
-      setOperationAction(ISD::FNEARBYINT, MVT::f64, Legal);
       setOperationAction(ISD::FROUND, MVT::f64, Legal);
 
       setOperationAction(ISD::FNEARBYINT, MVT::v4f32, Legal);
       setOperationAction(ISD::FROUND, MVT::v4f32, Legal);
-      setOperationAction(ISD::FNEARBYINT, MVT::f32, Legal);
       setOperationAction(ISD::FROUND, MVT::f32, Legal);
 
       setOperationAction(ISD::MUL, MVT::v2f64, Legal);

llvm/test/CodeGen/PowerPC/scalar-rounding-ops.ll

@@ -342,14 +342,14 @@ declare i64 @llvm.llround.i64.f32(float)
 
 define dso_local double @test_nearbyint(double %d) local_unnamed_addr {
 ; BE-LABEL: test_nearbyint:
-; BE:       # %bb.0: # %entry
-; BE-NEXT:    xsrdpic f1, f1
-; BE-NEXT:    blr
+; BE:    # %bb.0: # %entry
+; BE:    bl nearbyint
+; BE:    blr
 ;
 ; CHECK-LABEL: test_nearbyint:
-; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    xsrdpic f1, f1
-; CHECK-NEXT:    blr
+; CHECK:    # %bb.0: # %entry
+; CHECK:    bl nearbyint
+; CHECK:    blr
 ;
 ; FAST-LABEL: test_nearbyint:
 ; FAST:       # %bb.0: # %entry
@@ -364,14 +364,14 @@ declare double @llvm.nearbyint.f64(double)
 
 define dso_local float @test_nearbyintf(float %f) local_unnamed_addr {
 ; BE-LABEL: test_nearbyintf:
-; BE:       # %bb.0: # %entry
-; BE-NEXT:    xsrdpic f1, f1
-; BE-NEXT:    blr
+; BE:    # %bb.0: # %entry
+; BE:    bl nearbyint
+; BE:    blr
 ;
 ; CHECK-LABEL: test_nearbyintf:
-; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    xsrdpic f1, f1
-; CHECK-NEXT:    blr
+; CHECK:    # %bb.0: # %entry
+; CHECK:    bl nearbyintf
+; CHECK:    blr
 ;
 ; FAST-LABEL: test_nearbyintf:
 ; FAST:       # %bb.0: # %entry