AMDGPU: Directly select minimumnum/maximumnum with ieee_mode=0

llvm/lib/Target/AMDGPU/AMDGPUInstructions.td

@@ -92,6 +92,8 @@ def FP64Denormals : Predicate<"MF->getInfo<SIMachineFunctionInfo>()->getMode().F
 def NoFP16Denormals : Predicate<"MF->getInfo<SIMachineFunctionInfo>()->getMode().FP64FP16Denormals == DenormalMode::getPreserveSign()">;
 def NoFP32Denormals : Predicate<"MF->getInfo<SIMachineFunctionInfo>()->getMode().FP32Denormals == DenormalMode::getPreserveSign()">;
 def NoFP64Denormals : Predicate<"MF->getInfo<SIMachineFunctionInfo>()->getMode().FP64FP16Denormals == DenormalMode::getPreserveSign()">;
+def IEEEModeEnabled : Predicate<"MF->getInfo<SIMachineFunctionInfo>()->getMode().IEEE">;
+def IEEEModeDisabled : Predicate<"!MF->getInfo<SIMachineFunctionInfo>()->getMode().IEEE">;
 def UnsafeFPMath : Predicate<"TM.Options.UnsafeFPMath">;
 }
 

llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp

@@ -957,12 +957,9 @@ AMDGPULegalizerInfo::AMDGPULegalizerInfo(const GCNSubtarget &ST_,
     FPOpActions.clampMaxNumElementsStrict(0, S32, 2);
   }
 
-  auto &MinNumMaxNum = getActionDefinitionsBuilder({
-      G_FMINNUM, G_FMAXNUM, G_FMINNUM_IEEE, G_FMAXNUM_IEEE});
-
-  // TODO: These should be custom lowered and are directly legal with IEEE=0
-  auto &MinimumNumMaximumNum =
-      getActionDefinitionsBuilder({G_FMINIMUMNUM, G_FMAXIMUMNUM});
+  auto &MinNumMaxNum = getActionDefinitionsBuilder(
+      {G_FMINNUM, G_FMAXNUM, G_FMINIMUMNUM, G_FMAXIMUMNUM, G_FMINNUM_IEEE,
+       G_FMAXNUM_IEEE});
 
   if (ST.hasVOP3PInsts()) {
     MinNumMaxNum.customFor(FPTypesPK16)
@@ -980,8 +977,6 @@ AMDGPULegalizerInfo::AMDGPULegalizerInfo(const GCNSubtarget &ST_,
       .scalarize(0);
   }
 
-  MinimumNumMaximumNum.lower();
-
   if (ST.hasVOP3PInsts())
     FPOpActions.clampMaxNumElementsStrict(0, S16, 2);
 
@@ -2162,6 +2157,8 @@ bool AMDGPULegalizerInfo::legalizeCustom(
     return legalizeFPTOI(MI, MRI, B, false);
   case TargetOpcode::G_FMINNUM:
   case TargetOpcode::G_FMAXNUM:
+  case TargetOpcode::G_FMINIMUMNUM:
+  case TargetOpcode::G_FMAXIMUMNUM:
   case TargetOpcode::G_FMINNUM_IEEE:
   case TargetOpcode::G_FMAXNUM_IEEE:
     return legalizeMinNumMaxNum(Helper, MI);
@@ -2741,9 +2738,17 @@ bool AMDGPULegalizerInfo::legalizeMinNumMaxNum(LegalizerHelper &Helper,
                         MI.getOpcode() == AMDGPU::G_FMAXNUM_IEEE;
 
   // With ieee_mode disabled, the instructions have the correct behavior
-  // already for G_FMINNUM/G_FMAXNUM
-  if (!MFI->getMode().IEEE)
+  // already for G_FMINIMUMNUM/G_FMAXIMUMNUM.
+  //
+  // FIXME: G_FMINNUM/G_FMAXNUM should match the behavior with ieee_mode
+  // enabled.
+  if (!MFI->getMode().IEEE) {
+    if (MI.getOpcode() == AMDGPU::G_FMINIMUMNUM ||
+        MI.getOpcode() == AMDGPU::G_FMAXIMUMNUM)
+      return true;
+
     return !IsIEEEOp;
+  }
 
   if (IsIEEEOp)
     return true;

llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp

@@ -4009,6 +4009,8 @@ AMDGPURegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
   case AMDGPU::G_FMAXNUM:
   case AMDGPU::G_FMINIMUM:
   case AMDGPU::G_FMAXIMUM:
+  case AMDGPU::G_FMINIMUMNUM:
+  case AMDGPU::G_FMAXIMUMNUM:
   case AMDGPU::G_INTRINSIC_TRUNC:
   case AMDGPU::G_STRICT_FADD:
   case AMDGPU::G_STRICT_FSUB:

llvm/lib/Target/AMDGPU/SIISelLowering.cpp

@@ -531,8 +531,9 @@ SITargetLowering::SITargetLowering(const TargetMachine &TM,
     setOperationAction({ISD::SADDSAT, ISD::SSUBSAT}, {MVT::i16, MVT::i32},
                        Legal);
 
-  setOperationAction({ISD::FMINNUM, ISD::FMAXNUM}, {MVT::f32, MVT::f64},
-                     Custom);
+  setOperationAction(
+      {ISD::FMINNUM, ISD::FMAXNUM, ISD::FMINIMUMNUM, ISD::FMAXIMUMNUM},
+      {MVT::f32, MVT::f64}, Custom);
 
   // These are really only legal for ieee_mode functions. We should be avoiding
   // them for functions that don't have ieee_mode enabled, so just say they are
@@ -771,7 +772,9 @@ SITargetLowering::SITargetLowering(const TargetMachine &TM,
                         MVT::v32f16, MVT::v32bf16},
                        Custom);
 
-    setOperationAction({ISD::FMAXNUM, ISD::FMINNUM}, MVT::f16, Custom);
+    setOperationAction(
+        {ISD::FMAXNUM, ISD::FMINNUM, ISD::FMINIMUMNUM, ISD::FMAXIMUMNUM},
+        MVT::f16, Custom);
     setOperationAction({ISD::FMAXNUM_IEEE, ISD::FMINNUM_IEEE}, MVT::f16, Legal);
 
     setOperationAction({ISD::FMINNUM_IEEE, ISD::FMAXNUM_IEEE, ISD::FMINIMUMNUM,
@@ -825,8 +828,9 @@ SITargetLowering::SITargetLowering(const TargetMachine &TM,
       setOperationAction({ISD::FADD, ISD::FMUL, ISD::FMA, ISD::FCANONICALIZE},
                          VT, Custom);
 
-    setOperationAction({ISD::FMAXNUM, ISD::FMINNUM}, {MVT::v2f16, MVT::v4f16},
-                       Custom);
+    setOperationAction(
+        {ISD::FMAXNUM, ISD::FMINNUM, ISD::FMINIMUMNUM, ISD::FMAXIMUMNUM},
+        {MVT::v2f16, MVT::v4f16}, Custom);
 
     setOperationAction(ISD::FEXP, MVT::v2f16, Custom);
     setOperationAction(ISD::SELECT, {MVT::v4i16, MVT::v4f16, MVT::v4bf16},
@@ -6062,6 +6066,9 @@ SDValue SITargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
   case ISD::FMINNUM:
   case ISD::FMAXNUM:
     return lowerFMINNUM_FMAXNUM(Op, DAG);
+  case ISD::FMINIMUMNUM:
+  case ISD::FMAXIMUMNUM:
+    return lowerFMINIMUMNUM_FMAXIMUMNUM(Op, DAG);
   case ISD::FMINIMUM:
   case ISD::FMAXIMUM:
     return lowerFMINIMUM_FMAXIMUM(Op, DAG);
@@ -6086,8 +6093,6 @@ SDValue SITargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
   case ISD::FMUL:
   case ISD::FMINNUM_IEEE:
   case ISD::FMAXNUM_IEEE:
-  case ISD::FMINIMUMNUM:
-  case ISD::FMAXIMUMNUM:
   case ISD::UADDSAT:
   case ISD::USUBSAT:
   case ISD::SADDSAT:
@@ -6995,6 +7000,23 @@ SDValue SITargetLowering::lowerFMINNUM_FMAXNUM(SDValue Op,
   return Op;
 }
 
+SDValue
+SITargetLowering::lowerFMINIMUMNUM_FMAXIMUMNUM(SDValue Op,
+                                               SelectionDAG &DAG) const {
+  EVT VT = Op.getValueType();
+  const MachineFunction &MF = DAG.getMachineFunction();
+  const SIMachineFunctionInfo *Info = MF.getInfo<SIMachineFunctionInfo>();
+  bool IsIEEEMode = Info->getMode().IEEE;
+
+  if (IsIEEEMode)
+    return expandFMINIMUMNUM_FMAXIMUMNUM(Op.getNode(), DAG);
+
+  if (VT == MVT::v4f16 || VT == MVT::v8f16 || VT == MVT::v16f16 ||
+      VT == MVT::v16bf16)
+    return splitBinaryVectorOp(Op, DAG);
+  return Op;
+}
+
 SDValue SITargetLowering::lowerFMINIMUM_FMAXIMUM(SDValue Op,
                                                  SelectionDAG &DAG) const {
   EVT VT = Op.getValueType();

llvm/lib/Target/AMDGPU/SIISelLowering.h

@@ -147,6 +147,7 @@ class SITargetLowering final : public AMDGPUTargetLowering {
   SDValue lowerFP_ROUND(SDValue Op, SelectionDAG &DAG) const;
   SDValue splitFP_ROUNDVectorOp(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerFMINNUM_FMAXNUM(SDValue Op, SelectionDAG &DAG) const;
+  SDValue lowerFMINIMUMNUM_FMAXIMUMNUM(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerFMINIMUM_FMAXIMUM(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerFLDEXP(SDValue Op, SelectionDAG &DAG) const;
   SDValue promoteUniformOpToI32(SDValue Op, DAGCombinerInfo &DCI) const;

llvm/lib/Target/AMDGPU/SIInstructions.td

@@ -1390,6 +1390,55 @@ def : GCNPat<
   (S_ADD_U64_PSEUDO $src0, $src1)>;
 }
 
+//===----------------------------------------------------------------------===//
+// FP min/max patterns
+//===----------------------------------------------------------------------===//
+
+
+class FPBinOpPat <SDPatternOperator node, ValueType vt, Instruction inst>
+  : GCNPat <(vt (node (vt (VOP3Mods vt:$src0, i32:$src0_mods)),
+                      (vt (VOP3Mods vt:$src1, i32:$src1_mods)))),
+    (inst $src0_mods, $src0, $src1_mods, $src1, DSTCLAMP.NONE, DSTOMOD.NONE)
+>;
+
+class FPPkBinOpPat <SDPatternOperator node, ValueType vt, Instruction inst>
+  : GCNPat <(vt (node (VOP3PMods v2f16:$src0, i32:$src0_mods),
+                      (VOP3PMods v2f16:$src1, i32:$src1_mods))),
+  (inst $src0_mods, $src0, $src1_mods, $src1, DSTCLAMP.NONE)
+>;
+
+/// With IEEE=0, signalingness is ignored and the non-nan input will
+/// be directly returned.
+let OtherPredicates = [IEEEModeDisabled] in {
+  def : FPBinOpPat<fminimumnum, f32, V_MIN_F32_e64>;
+  def : FPBinOpPat<fmaximumnum, f32, V_MAX_F32_e64>;
+  def : FPBinOpPat<fminimumnum, f64, V_MIN_F64_e64>;
+  def : FPBinOpPat<fmaximumnum, f64, V_MAX_F64_e64>;
+
+  let SubtargetPredicate = Has16BitInsts,
+      True16Predicate = NotHasTrue16BitInsts in {
+    def : FPBinOpPat<fminimumnum, f16, V_MIN_F16_e64>;
+    def : FPBinOpPat<fmaximumnum, f16, V_MAX_F16_e64>;
+  }
+
+  let SubtargetPredicate = Has16BitInsts,
+      True16Predicate = UseRealTrue16Insts in {
+    def : FPBinOpPat<fminimumnum, f16, V_MIN_F16_t16_e64>;
+    def : FPBinOpPat<fmaximumnum, f16, V_MAX_F16_t16_e64>;
+  }
+
+  let SubtargetPredicate = Has16BitInsts,
+      True16Predicate = UseFakeTrue16Insts in {
+    def : FPBinOpPat<fminimumnum, f16, V_MIN_F16_fake16_e64>;
+    def : FPBinOpPat<fmaximumnum, f16, V_MAX_F16_fake16_e64>;
+  }
+
+  let SubtargetPredicate = HasVOP3PInsts in {
+    def : FPPkBinOpPat<fminimumnum, v2f16, V_PK_MIN_F16>;
+    def : FPPkBinOpPat<fmaximumnum, v2f16, V_PK_MAX_F16>;
+  }
+}
+
 /********** ============================================ **********/
 /********** Extraction, Insertion, Building and Casting  **********/
 /********** ============================================ **********/

llvm/test/CodeGen/AMDGPU/fneg-combines.new.ll

@@ -2019,9 +2019,7 @@ define float @v_fneg_minimumnum_f32_no_ieee(float %a, float %b) #4 {
 ; GCN-LABEL: v_fneg_minimumnum_f32_no_ieee:
 ; GCN:       ; %bb.0:
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; GCN-NEXT:    v_mul_f32_e32 v1, -1.0, v1
-; GCN-NEXT:    v_mul_f32_e32 v0, -1.0, v0
-; GCN-NEXT:    v_max_f32_e32 v0, v0, v1
+; GCN-NEXT:    v_max_f32_e64 v0, -v0, -v1
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %min = call float @llvm.minimumnum.f32(float %a, float %b)
   %fneg = fneg float %min
@@ -2044,8 +2042,7 @@ define float @v_fneg_self_minimumnum_f32_no_ieee(float %a) #4 {
 ; GCN-LABEL: v_fneg_self_minimumnum_f32_no_ieee:
 ; GCN:       ; %bb.0:
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; GCN-NEXT:    v_mul_f32_e32 v0, -1.0, v0
-; GCN-NEXT:    v_max_f32_e32 v0, v0, v0
+; GCN-NEXT:    v_max_f32_e64 v0, -v0, -v0
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %min = call float @llvm.minimumnum.f32(float %a, float %a)
   %min.fneg = fneg float %min
@@ -2068,8 +2065,7 @@ define float @v_fneg_posk_minimumnum_f32_no_ieee(float %a) #4 {
 ; GCN-LABEL: v_fneg_posk_minimumnum_f32_no_ieee:
 ; GCN:       ; %bb.0:
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; GCN-NEXT:    v_mul_f32_e32 v0, -1.0, v0
-; GCN-NEXT:    v_max_f32_e32 v0, -4.0, v0
+; GCN-NEXT:    v_max_f32_e64 v0, -v0, -4.0
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %min = call float @llvm.minimumnum.f32(float 4.0, float %a)
   %fneg = fneg float %min
@@ -2092,8 +2088,7 @@ define float @v_fneg_negk_minimumnum_f32_no_ieee(float %a) #4 {
 ; GCN-LABEL: v_fneg_negk_minimumnum_f32_no_ieee:
 ; GCN:       ; %bb.0:
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; GCN-NEXT:    v_mul_f32_e32 v0, -1.0, v0
-; GCN-NEXT:    v_max_f32_e32 v0, 4.0, v0
+; GCN-NEXT:    v_max_f32_e64 v0, -v0, 4.0
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %min = call float @llvm.minimumnum.f32(float -4.0, float %a)
   %fneg = fneg float %min
@@ -2251,8 +2246,7 @@ define float @v_fneg_neg0_minimumnum_f32_no_ieee(float %a) #4 {
 ; GCN-LABEL: v_fneg_neg0_minimumnum_f32_no_ieee:
 ; GCN:       ; %bb.0:
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; GCN-NEXT:    v_mul_f32_e32 v0, -1.0, v0
-; GCN-NEXT:    v_max_f32_e32 v0, 0, v0
+; GCN-NEXT:    v_max_f32_e64 v0, -v0, 0
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %min = call float @llvm.minimumnum.f32(float -0.0, float %a)
   %fneg = fneg float %min
@@ -2299,7 +2293,6 @@ define float @v_fneg_0_minimumnum_foldable_use_f32_no_ieee(float %a, float %b) #
 ; GCN-LABEL: v_fneg_0_minimumnum_foldable_use_f32_no_ieee:
 ; GCN:       ; %bb.0:
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; GCN-NEXT:    v_mul_f32_e32 v0, 1.0, v0
 ; GCN-NEXT:    v_min_f32_e32 v0, 0, v0
 ; GCN-NEXT:    v_mul_f32_e64 v0, -v0, v1
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
@@ -2330,9 +2323,7 @@ define <2 x float> @v_fneg_minimumnum_multi_use_minimumnum_f32_no_ieee(float %a,
 ; GCN-LABEL: v_fneg_minimumnum_multi_use_minimumnum_f32_no_ieee:
 ; GCN:       ; %bb.0:
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; GCN-NEXT:    v_mul_f32_e32 v1, -1.0, v1
-; GCN-NEXT:    v_mul_f32_e32 v0, -1.0, v0
-; GCN-NEXT:    v_max_f32_e32 v0, v0, v1
+; GCN-NEXT:    v_max_f32_e64 v0, -v0, -v1
 ; GCN-NEXT:    v_mul_f32_e32 v1, -4.0, v0
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %min = call float @llvm.minimumnum.f32(float %a, float %b)
@@ -2364,9 +2355,7 @@ define float @v_fneg_maximumnum_f32_no_ieee(float %a, float %b) #4 {
 ; GCN-LABEL: v_fneg_maximumnum_f32_no_ieee:
 ; GCN:       ; %bb.0:
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; GCN-NEXT:    v_mul_f32_e32 v1, -1.0, v1
-; GCN-NEXT:    v_mul_f32_e32 v0, -1.0, v0
-; GCN-NEXT:    v_min_f32_e32 v0, v0, v1
+; GCN-NEXT:    v_min_f32_e64 v0, -v0, -v1
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %max = call float @llvm.maximumnum.f32(float %a, float %b)
   %fneg = fneg float %max
@@ -2389,8 +2378,7 @@ define float @v_fneg_self_maximumnum_f32_no_ieee(float %a) #4 {
 ; GCN-LABEL: v_fneg_self_maximumnum_f32_no_ieee:
 ; GCN:       ; %bb.0:
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; GCN-NEXT:    v_mul_f32_e32 v0, -1.0, v0
-; GCN-NEXT:    v_min_f32_e32 v0, v0, v0
+; GCN-NEXT:    v_min_f32_e64 v0, -v0, -v0
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %max = call float @llvm.maximumnum.f32(float %a, float %a)
   %max.fneg = fneg float %max
@@ -2413,8 +2401,7 @@ define float @v_fneg_posk_maximumnum_f32_no_ieee(float %a) #4 {
 ; GCN-LABEL: v_fneg_posk_maximumnum_f32_no_ieee:
 ; GCN:       ; %bb.0:
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; GCN-NEXT:    v_mul_f32_e32 v0, -1.0, v0
-; GCN-NEXT:    v_min_f32_e32 v0, -4.0, v0
+; GCN-NEXT:    v_min_f32_e64 v0, -v0, -4.0
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %max = call float @llvm.maximumnum.f32(float 4.0, float %a)
   %fneg = fneg float %max
@@ -2437,8 +2424,7 @@ define float @v_fneg_negk_maximumnum_f32_no_ieee(float %a) #4 {
 ; GCN-LABEL: v_fneg_negk_maximumnum_f32_no_ieee:
 ; GCN:       ; %bb.0:
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; GCN-NEXT:    v_mul_f32_e32 v0, -1.0, v0
-; GCN-NEXT:    v_min_f32_e32 v0, 4.0, v0
+; GCN-NEXT:    v_min_f32_e64 v0, -v0, 4.0
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %max = call float @llvm.maximumnum.f32(float -4.0, float %a)
   %fneg = fneg float %max
@@ -2473,8 +2459,7 @@ define float @v_fneg_neg0_maximumnum_f32_no_ieee(float %a) #4 {
 ; GCN-LABEL: v_fneg_neg0_maximumnum_f32_no_ieee:
 ; GCN:       ; %bb.0:
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; GCN-NEXT:    v_mul_f32_e32 v0, -1.0, v0
-; GCN-NEXT:    v_min_f32_e32 v0, 0, v0
+; GCN-NEXT:    v_min_f32_e64 v0, -v0, 0
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %max = call float @llvm.maximumnum.f32(float -0.0, float %a)
   %fneg = fneg float %max
@@ -2499,7 +2484,6 @@ define float @v_fneg_0_maximumnum_foldable_use_f32_no_ieee(float %a, float %b) #
 ; GCN-LABEL: v_fneg_0_maximumnum_foldable_use_f32_no_ieee:
 ; GCN:       ; %bb.0:
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; GCN-NEXT:    v_mul_f32_e32 v0, 1.0, v0
 ; GCN-NEXT:    v_max_f32_e32 v0, 0, v0
 ; GCN-NEXT:    v_mul_f32_e64 v0, -v0, v1
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
@@ -2530,9 +2514,7 @@ define <2 x float> @v_fneg_maximumnum_multi_use_maximumnum_f32_no_ieee(float %a,
 ; GCN-LABEL: v_fneg_maximumnum_multi_use_maximumnum_f32_no_ieee:
 ; GCN:       ; %bb.0:
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; GCN-NEXT:    v_mul_f32_e32 v1, -1.0, v1
-; GCN-NEXT:    v_mul_f32_e32 v0, -1.0, v0
-; GCN-NEXT:    v_min_f32_e32 v0, v0, v1
+; GCN-NEXT:    v_min_f32_e64 v0, -v0, -v1
 ; GCN-NEXT:    v_mul_f32_e32 v1, -4.0, v0
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %max = call float @llvm.maximumnum.f32(float %a, float %b)