DAG: Add AssertNoFPClass from call return attributes (#167264)

This defends against regressions in future patches. This excludes
the target intrinsic case for now; I'm worried introducing an
intermediate
AssertNoFPClass is likely to break combines.

Author: arsenm

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -4638,6 +4638,12 @@ static std::optional<ConstantRange> getRange(const Instruction &I) {
   return std::nullopt;
 }
 
+static FPClassTest getNoFPClass(const Instruction &I) {
+  if (const auto *CB = dyn_cast<CallBase>(&I))
+    return CB->getRetNoFPClass();
+  return fcNone;
+}
+
 void SelectionDAGBuilder::visitLoad(const LoadInst &I) {
   if (I.isAtomic())
     return visitAtomicLoad(I);
@@ -9132,6 +9138,7 @@ void SelectionDAGBuilder::LowerCallTo(const CallBase &CB, SDValue Callee,
 
   if (Result.first.getNode()) {
     Result.first = lowerRangeToAssertZExt(DAG, CB, Result.first);
+    Result.first = lowerNoFPClassToAssertNoFPClass(DAG, CB, Result.first);
     setValue(&CB, Result.first);
   }
 
@@ -10718,6 +10725,16 @@ SDValue SelectionDAGBuilder::lowerRangeToAssertZExt(SelectionDAG &DAG,
   return DAG.getMergeValues(Ops, SL);
 }
 
+SDValue SelectionDAGBuilder::lowerNoFPClassToAssertNoFPClass(
+    SelectionDAG &DAG, const Instruction &I, SDValue Op) {
+  FPClassTest Classes = getNoFPClass(I);
+  if (Classes == fcNone)
+    return Op;
+
+  return DAG.getNode(ISD::AssertNoFPClass, SDLoc(Op), Op.getValueType(), Op,
+                     DAG.getTargetConstant(Classes, SDLoc(), MVT::i32));
+}
+
 /// Populate a CallLowerinInfo (into \p CLI) based on the properties of
 /// the call being lowered.
 ///

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h

@@ -429,6 +429,10 @@ class SelectionDAGBuilder {
   SDValue lowerRangeToAssertZExt(SelectionDAG &DAG, const Instruction &I,
                                  SDValue Op);
 
+  // Lower nofpclass attributes to AssertNoFPClass
+  SDValue lowerNoFPClassToAssertNoFPClass(SelectionDAG &DAG,
+                                          const Instruction &I, SDValue Op);
+
   void populateCallLoweringInfo(TargetLowering::CallLoweringInfo &CLI,
                                 const CallBase *Call, unsigned ArgIdx,
                                 unsigned NumArgs, SDValue Callee,

llvm/test/CodeGen/AMDGPU/nofpclass-call.ll

@@ -35,9 +35,7 @@ define float @call_nofpclass_funcs_f32(ptr addrspace(1) %ptr) {
 ; CHECK-NEXT:    v_mov_b32_e32 v3, v0
 ; CHECK-NEXT:    v_mov_b32_e32 v0, v2
 ; CHECK-NEXT:    s_swappc_b64 s[30:31], s[16:17]
-; CHECK-NEXT:    v_max_f32_e32 v1, v3, v3
-; CHECK-NEXT:    v_max_f32_e32 v0, v0, v0
-; CHECK-NEXT:    v_min_f32_e32 v0, v1, v0
+; CHECK-NEXT:    v_min_f32_e32 v0, v3, v0
 ; CHECK-NEXT:    v_readlane_b32 s31, v4, 1
 ; CHECK-NEXT:    v_readlane_b32 s30, v4, 0
 ; CHECK-NEXT:    s_mov_b32 s32, s33
@@ -87,12 +85,8 @@ define <2 x float> @call_nofpclass_funcs_v2f32(ptr addrspace(1) %ptr) {
 ; CHECK-NEXT:    v_mov_b32_e32 v0, v3
 ; CHECK-NEXT:    v_mov_b32_e32 v1, v2
 ; CHECK-NEXT:    s_swappc_b64 s[30:31], s[16:17]
-; CHECK-NEXT:    v_max_f32_e32 v2, v4, v4
-; CHECK-NEXT:    v_max_f32_e32 v0, v0, v0
-; CHECK-NEXT:    v_min_f32_e32 v0, v2, v0
-; CHECK-NEXT:    v_max_f32_e32 v2, v5, v5
-; CHECK-NEXT:    v_max_f32_e32 v1, v1, v1
-; CHECK-NEXT:    v_min_f32_e32 v1, v2, v1
+; CHECK-NEXT:    v_min_f32_e32 v0, v4, v0
+; CHECK-NEXT:    v_min_f32_e32 v1, v5, v1
 ; CHECK-NEXT:    v_readlane_b32 s31, v6, 1
 ; CHECK-NEXT:    v_readlane_b32 s30, v6, 0
 ; CHECK-NEXT:    s_mov_b32 s32, s33
@@ -142,12 +136,10 @@ define double @call_nofpclass_funcs_f64(ptr addrspace(1) %ptr) {
 ; CHECK-NEXT:    v_mov_b32_e32 v0, v5
 ; CHECK-NEXT:    v_mov_b32_e32 v1, v4
 ; CHECK-NEXT:    s_swappc_b64 s[30:31], s[16:17]
-; CHECK-NEXT:    v_max_f64 v[2:3], v[2:3], v[2:3]
-; CHECK-NEXT:    v_max_f64 v[0:1], v[0:1], v[0:1]
+; CHECK-NEXT:    v_min_f64 v[0:1], v[2:3], v[0:1]
 ; CHECK-NEXT:    v_readlane_b32 s31, v6, 1
 ; CHECK-NEXT:    v_readlane_b32 s30, v6, 0
 ; CHECK-NEXT:    s_mov_b32 s32, s33
-; CHECK-NEXT:    v_min_f64 v[0:1], v[2:3], v[0:1]
 ; CHECK-NEXT:    s_xor_saveexec_b64 s[4:5], -1
 ; CHECK-NEXT:    buffer_load_dword v6, off, s[0:3], s33 ; 4-byte Folded Reload
 ; CHECK-NEXT:    s_mov_b64 exec, s[4:5]