DAG: Skip 0 sign handling in minimum/maximum lowering for _ieee case (#91326)

dc9664a changed the documentation to
assume these order -0 as less than +0.

Author: arsenm

llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

@@ -8401,8 +8401,14 @@ SDValue TargetLowering::expandFMINIMUM_FMAXIMUM(SDNode *N,
   SDValue MinMax;
   unsigned CompOpcIeee = IsMax ? ISD::FMAXNUM_IEEE : ISD::FMINNUM_IEEE;
   unsigned CompOpc = IsMax ? ISD::FMAXNUM : ISD::FMINNUM;
+
+  // FIXME: We should probably define fminnum/fmaxnum variants with correct
+  // signed zero behavior.
+  bool MinMaxMustRespectOrderedZero = false;
+
   if (isOperationLegalOrCustom(CompOpcIeee, VT)) {
     MinMax = DAG.getNode(CompOpcIeee, DL, VT, LHS, RHS);
+    MinMaxMustRespectOrderedZero = true;
   } else if (isOperationLegalOrCustom(CompOpc, VT)) {
     MinMax = DAG.getNode(CompOpc, DL, VT, LHS, RHS);
   } else {
@@ -8422,8 +8428,8 @@ SDValue TargetLowering::expandFMINIMUM_FMAXIMUM(SDNode *N,
   }
 
   // fminimum/fmaximum requires -0.0 less than +0.0
-  if (!N->getFlags().hasNoSignedZeros() && !DAG.isKnownNeverZeroFloat(RHS) &&
-      !DAG.isKnownNeverZeroFloat(LHS)) {
+  if (!MinMaxMustRespectOrderedZero && !N->getFlags().hasNoSignedZeros() &&
+      !DAG.isKnownNeverZeroFloat(RHS) && !DAG.isKnownNeverZeroFloat(LHS)) {
     SDValue IsZero = DAG.getSetCC(DL, CCVT, MinMax,
                                   DAG.getConstantFP(0.0, DL, VT), ISD::SETEQ);
     SDValue TestZero =

llvm/test/CodeGen/AMDGPU/llvm.maximum.f16.ll

@@ -45,74 +45,26 @@ define float @f32_minimum(float %a, float %b) {
 ;
 ; VSX-LABEL: f32_minimum:
 ; VSX:       # %bb.0: # %entry
-; VSX-NEXT:    xscvdpspn 0, 1
 ; VSX-NEXT:    fcmpu 0, 1, 2
-; VSX-NEXT:    xscvdpspn 3, 2
-; VSX-NEXT:    mffprwz 3, 0
 ; VSX-NEXT:    bc 12, 3, .LBB0_2
 ; VSX-NEXT:  # %bb.1: # %entry
-; VSX-NEXT:    xsmindp 0, 1, 2
-; VSX-NEXT:    b .LBB0_3
+; VSX-NEXT:    xsmindp 1, 1, 2
+; VSX-NEXT:    blr
 ; VSX-NEXT:  .LBB0_2:
-; VSX-NEXT:    addis 4, 2, .LCPI0_0@toc@ha
-; VSX-NEXT:    lfs 0, .LCPI0_0@toc@l(4)
-; VSX-NEXT:  .LBB0_3: # %entry
-; VSX-NEXT:    xoris 3, 3, 32768
-; VSX-NEXT:    mffprwz 4, 3
-; VSX-NEXT:    cmplwi 3, 0
-; VSX-NEXT:    bc 12, 2, .LBB0_5
-; VSX-NEXT:  # %bb.4: # %entry
-; VSX-NEXT:    fmr 1, 0
-; VSX-NEXT:  .LBB0_5: # %entry
-; VSX-NEXT:    xoris 3, 4, 32768
-; VSX-NEXT:    cmplwi 3, 0
-; VSX-NEXT:    bc 12, 2, .LBB0_7
-; VSX-NEXT:  # %bb.6: # %entry
-; VSX-NEXT:    fmr 2, 1
-; VSX-NEXT:  .LBB0_7: # %entry
-; VSX-NEXT:    xxlxor 1, 1, 1
-; VSX-NEXT:    fcmpu 0, 0, 1
-; VSX-NEXT:    bc 12, 2, .LBB0_9
-; VSX-NEXT:  # %bb.8: # %entry
-; VSX-NEXT:    fmr 2, 0
-; VSX-NEXT:  .LBB0_9: # %entry
-; VSX-NEXT:    fmr 1, 2
+; VSX-NEXT:    addis 3, 2, .LCPI0_0@toc@ha
+; VSX-NEXT:    lfs 1, .LCPI0_0@toc@l(3)
 ; VSX-NEXT:    blr
 ;
 ; AIX-LABEL: f32_minimum:
 ; AIX:       # %bb.0: # %entry
-; AIX-NEXT:    xscvdpspn 0, 1
 ; AIX-NEXT:    fcmpu 0, 1, 2
-; AIX-NEXT:    xscvdpspn 3, 2
-; AIX-NEXT:    mffprwz 3, 0
 ; AIX-NEXT:    bc 12, 3, L..BB0_2
 ; AIX-NEXT:  # %bb.1: # %entry
-; AIX-NEXT:    xsmindp 0, 1, 2
-; AIX-NEXT:    b L..BB0_3
+; AIX-NEXT:    xsmindp 1, 1, 2
+; AIX-NEXT:    blr
 ; AIX-NEXT:  L..BB0_2:
-; AIX-NEXT:    ld 4, L..C0(2) # %const.0
-; AIX-NEXT:    lfs 0, 0(4)
-; AIX-NEXT:  L..BB0_3: # %entry
-; AIX-NEXT:    xoris 3, 3, 32768
-; AIX-NEXT:    mffprwz 4, 3
-; AIX-NEXT:    cmplwi 3, 0
-; AIX-NEXT:    bc 12, 2, L..BB0_5
-; AIX-NEXT:  # %bb.4: # %entry
-; AIX-NEXT:    fmr 1, 0
-; AIX-NEXT:  L..BB0_5: # %entry
-; AIX-NEXT:    xoris 3, 4, 32768
-; AIX-NEXT:    cmplwi 3, 0
-; AIX-NEXT:    bc 12, 2, L..BB0_7
-; AIX-NEXT:  # %bb.6: # %entry
-; AIX-NEXT:    fmr 2, 1
-; AIX-NEXT:  L..BB0_7: # %entry
-; AIX-NEXT:    xxlxor 1, 1, 1
-; AIX-NEXT:    fcmpu 0, 0, 1
-; AIX-NEXT:    bc 12, 2, L..BB0_9
-; AIX-NEXT:  # %bb.8: # %entry
-; AIX-NEXT:    fmr 2, 0
-; AIX-NEXT:  L..BB0_9: # %entry
-; AIX-NEXT:    fmr 1, 2
+; AIX-NEXT:    ld 3, L..C0(2) # %const.0
+; AIX-NEXT:    lfs 1, 0(3)
 ; AIX-NEXT:    blr
 entry:
   %m = call float @llvm.minimum.f32(float %a, float %b)
@@ -159,70 +111,26 @@ define float @f32_maximum(float %a, float %b) {
 ;
 ; VSX-LABEL: f32_maximum:
 ; VSX:       # %bb.0: # %entry
-; VSX-NEXT:    xscvdpspn 0, 1
 ; VSX-NEXT:    fcmpu 0, 1, 2
-; VSX-NEXT:    xscvdpspn 3, 2
-; VSX-NEXT:    mffprwz 3, 0
 ; VSX-NEXT:    bc 12, 3, .LBB1_2
 ; VSX-NEXT:  # %bb.1: # %entry
-; VSX-NEXT:    xsmaxdp 0, 1, 2
-; VSX-NEXT:    b .LBB1_3
+; VSX-NEXT:    xsmaxdp 1, 1, 2
+; VSX-NEXT:    blr
 ; VSX-NEXT:  .LBB1_2:
-; VSX-NEXT:    addis 4, 2, .LCPI1_0@toc@ha
-; VSX-NEXT:    lfs 0, .LCPI1_0@toc@l(4)
-; VSX-NEXT:  .LBB1_3: # %entry
-; VSX-NEXT:    mffprwz 4, 3
-; VSX-NEXT:    cmpwi 3, 0
-; VSX-NEXT:    bc 12, 2, .LBB1_5
-; VSX-NEXT:  # %bb.4: # %entry
-; VSX-NEXT:    fmr 1, 0
-; VSX-NEXT:  .LBB1_5: # %entry
-; VSX-NEXT:    cmpwi 4, 0
-; VSX-NEXT:    bc 12, 2, .LBB1_7
-; VSX-NEXT:  # %bb.6: # %entry
-; VSX-NEXT:    fmr 2, 1
-; VSX-NEXT:  .LBB1_7: # %entry
-; VSX-NEXT:    xxlxor 1, 1, 1
-; VSX-NEXT:    fcmpu 0, 0, 1
-; VSX-NEXT:    bc 12, 2, .LBB1_9
-; VSX-NEXT:  # %bb.8: # %entry
-; VSX-NEXT:    fmr 2, 0
-; VSX-NEXT:  .LBB1_9: # %entry
-; VSX-NEXT:    fmr 1, 2
+; VSX-NEXT:    addis 3, 2, .LCPI1_0@toc@ha
+; VSX-NEXT:    lfs 1, .LCPI1_0@toc@l(3)
 ; VSX-NEXT:    blr
 ;
 ; AIX-LABEL: f32_maximum:
 ; AIX:       # %bb.0: # %entry
-; AIX-NEXT:    xscvdpspn 0, 1
 ; AIX-NEXT:    fcmpu 0, 1, 2
-; AIX-NEXT:    xscvdpspn 3, 2
-; AIX-NEXT:    mffprwz 3, 0
 ; AIX-NEXT:    bc 12, 3, L..BB1_2
 ; AIX-NEXT:  # %bb.1: # %entry
-; AIX-NEXT:    xsmaxdp 0, 1, 2
-; AIX-NEXT:    b L..BB1_3
+; AIX-NEXT:    xsmaxdp 1, 1, 2
+; AIX-NEXT:    blr
 ; AIX-NEXT:  L..BB1_2:
-; AIX-NEXT:    ld 4, L..C1(2) # %const.0
-; AIX-NEXT:    lfs 0, 0(4)
-; AIX-NEXT:  L..BB1_3: # %entry
-; AIX-NEXT:    mffprwz 4, 3
-; AIX-NEXT:    cmpwi 3, 0
-; AIX-NEXT:    bc 12, 2, L..BB1_5
-; AIX-NEXT:  # %bb.4: # %entry
-; AIX-NEXT:    fmr 1, 0
-; AIX-NEXT:  L..BB1_5: # %entry
-; AIX-NEXT:    cmpwi 4, 0
-; AIX-NEXT:    bc 12, 2, L..BB1_7
-; AIX-NEXT:  # %bb.6: # %entry
-; AIX-NEXT:    fmr 2, 1
-; AIX-NEXT:  L..BB1_7: # %entry
-; AIX-NEXT:    xxlxor 1, 1, 1
-; AIX-NEXT:    fcmpu 0, 0, 1
-; AIX-NEXT:    bc 12, 2, L..BB1_9
-; AIX-NEXT:  # %bb.8: # %entry
-; AIX-NEXT:    fmr 2, 0
-; AIX-NEXT:  L..BB1_9: # %entry
-; AIX-NEXT:    fmr 1, 2
+; AIX-NEXT:    ld 3, L..C1(2) # %const.0
+; AIX-NEXT:    lfs 1, 0(3)
 ; AIX-NEXT:    blr
 entry:
   %m = call float @llvm.maximum.f32(float %a, float %b)
@@ -272,69 +180,25 @@ define double @f64_minimum(double %a, double %b) {
 ; VSX-LABEL: f64_minimum:
 ; VSX:       # %bb.0: # %entry
 ; VSX-NEXT:    fcmpu 0, 1, 2
-; VSX-NEXT:    mffprd 3, 1
 ; VSX-NEXT:    bc 12, 3, .LBB2_2
 ; VSX-NEXT:  # %bb.1: # %entry
-; VSX-NEXT:    xsmindp 0, 1, 2
-; VSX-NEXT:    b .LBB2_3
+; VSX-NEXT:    xsmindp 1, 1, 2
+; VSX-NEXT:    blr
 ; VSX-NEXT:  .LBB2_2:
-; VSX-NEXT:    addis 4, 2, .LCPI2_0@toc@ha
-; VSX-NEXT:    lfs 0, .LCPI2_0@toc@l(4)
-; VSX-NEXT:  .LBB2_3: # %entry
-; VSX-NEXT:    li 5, 1
-; VSX-NEXT:    mffprd 4, 2
-; VSX-NEXT:    rldic 5, 5, 63, 0
-; VSX-NEXT:    cmpd 3, 5
-; VSX-NEXT:    bc 12, 2, .LBB2_5
-; VSX-NEXT:  # %bb.4: # %entry
-; VSX-NEXT:    fmr 1, 0
-; VSX-NEXT:  .LBB2_5: # %entry
-; VSX-NEXT:    cmpd 4, 5
-; VSX-NEXT:    bc 12, 2, .LBB2_7
-; VSX-NEXT:  # %bb.6: # %entry
-; VSX-NEXT:    fmr 2, 1
-; VSX-NEXT:  .LBB2_7: # %entry
-; VSX-NEXT:    xxlxor 1, 1, 1
-; VSX-NEXT:    fcmpu 0, 0, 1
-; VSX-NEXT:    bc 12, 2, .LBB2_9
-; VSX-NEXT:  # %bb.8: # %entry
-; VSX-NEXT:    fmr 2, 0
-; VSX-NEXT:  .LBB2_9: # %entry
-; VSX-NEXT:    fmr 1, 2
+; VSX-NEXT:    addis 3, 2, .LCPI2_0@toc@ha
+; VSX-NEXT:    lfs 1, .LCPI2_0@toc@l(3)
 ; VSX-NEXT:    blr
 ;
 ; AIX-LABEL: f64_minimum:
 ; AIX:       # %bb.0: # %entry
 ; AIX-NEXT:    fcmpu 0, 1, 2
-; AIX-NEXT:    mffprd 3, 1
 ; AIX-NEXT:    bc 12, 3, L..BB2_2
 ; AIX-NEXT:  # %bb.1: # %entry
-; AIX-NEXT:    xsmindp 0, 1, 2
-; AIX-NEXT:    b L..BB2_3
+; AIX-NEXT:    xsmindp 1, 1, 2
+; AIX-NEXT:    blr
 ; AIX-NEXT:  L..BB2_2:
-; AIX-NEXT:    ld 4, L..C2(2) # %const.0
-; AIX-NEXT:    lfs 0, 0(4)
-; AIX-NEXT:  L..BB2_3: # %entry
-; AIX-NEXT:    li 5, 1
-; AIX-NEXT:    mffprd 4, 2
-; AIX-NEXT:    rldic 5, 5, 63, 0
-; AIX-NEXT:    cmpd 3, 5
-; AIX-NEXT:    bc 12, 2, L..BB2_5
-; AIX-NEXT:  # %bb.4: # %entry
-; AIX-NEXT:    fmr 1, 0
-; AIX-NEXT:  L..BB2_5: # %entry
-; AIX-NEXT:    cmpd 4, 5
-; AIX-NEXT:    bc 12, 2, L..BB2_7
-; AIX-NEXT:  # %bb.6: # %entry
-; AIX-NEXT:    fmr 2, 1
-; AIX-NEXT:  L..BB2_7: # %entry
-; AIX-NEXT:    xxlxor 1, 1, 1
-; AIX-NEXT:    fcmpu 0, 0, 1
-; AIX-NEXT:    bc 12, 2, L..BB2_9
-; AIX-NEXT:  # %bb.8: # %entry
-; AIX-NEXT:    fmr 2, 0
-; AIX-NEXT:  L..BB2_9: # %entry
-; AIX-NEXT:    fmr 1, 2
+; AIX-NEXT:    ld 3, L..C2(2) # %const.0
+; AIX-NEXT:    lfs 1, 0(3)
 ; AIX-NEXT:    blr
 entry:
   %m = call double @llvm.minimum.f64(double %a, double %b)
@@ -382,65 +246,25 @@ define double @f64_maximum(double %a, double %b) {
 ; VSX-LABEL: f64_maximum:
 ; VSX:       # %bb.0: # %entry
 ; VSX-NEXT:    fcmpu 0, 1, 2
-; VSX-NEXT:    mffprd 3, 1
 ; VSX-NEXT:    bc 12, 3, .LBB3_2
 ; VSX-NEXT:  # %bb.1: # %entry
-; VSX-NEXT:    xsmaxdp 0, 1, 2
-; VSX-NEXT:    b .LBB3_3
+; VSX-NEXT:    xsmaxdp 1, 1, 2
+; VSX-NEXT:    blr
 ; VSX-NEXT:  .LBB3_2:
-; VSX-NEXT:    addis 4, 2, .LCPI3_0@toc@ha
-; VSX-NEXT:    lfs 0, .LCPI3_0@toc@l(4)
-; VSX-NEXT:  .LBB3_3: # %entry
-; VSX-NEXT:    mffprd 4, 2
-; VSX-NEXT:    cmpdi 3, 0
-; VSX-NEXT:    bc 12, 2, .LBB3_5
-; VSX-NEXT:  # %bb.4: # %entry
-; VSX-NEXT:    fmr 1, 0
-; VSX-NEXT:  .LBB3_5: # %entry
-; VSX-NEXT:    cmpdi 4, 0
-; VSX-NEXT:    bc 12, 2, .LBB3_7
-; VSX-NEXT:  # %bb.6: # %entry
-; VSX-NEXT:    fmr 2, 1
-; VSX-NEXT:  .LBB3_7: # %entry
-; VSX-NEXT:    xxlxor 1, 1, 1
-; VSX-NEXT:    fcmpu 0, 0, 1
-; VSX-NEXT:    bc 12, 2, .LBB3_9
-; VSX-NEXT:  # %bb.8: # %entry
-; VSX-NEXT:    fmr 2, 0
-; VSX-NEXT:  .LBB3_9: # %entry
-; VSX-NEXT:    fmr 1, 2
+; VSX-NEXT:    addis 3, 2, .LCPI3_0@toc@ha
+; VSX-NEXT:    lfs 1, .LCPI3_0@toc@l(3)
 ; VSX-NEXT:    blr
 ;
 ; AIX-LABEL: f64_maximum:
 ; AIX:       # %bb.0: # %entry
 ; AIX-NEXT:    fcmpu 0, 1, 2
-; AIX-NEXT:    mffprd 3, 1
 ; AIX-NEXT:    bc 12, 3, L..BB3_2
 ; AIX-NEXT:  # %bb.1: # %entry
-; AIX-NEXT:    xsmaxdp 0, 1, 2
-; AIX-NEXT:    b L..BB3_3
+; AIX-NEXT:    xsmaxdp 1, 1, 2
+; AIX-NEXT:    blr
 ; AIX-NEXT:  L..BB3_2:
-; AIX-NEXT:    ld 4, L..C3(2) # %const.0
-; AIX-NEXT:    lfs 0, 0(4)
-; AIX-NEXT:  L..BB3_3: # %entry
-; AIX-NEXT:    mffprd 4, 2
-; AIX-NEXT:    cmpdi 3, 0
-; AIX-NEXT:    bc 12, 2, L..BB3_5
-; AIX-NEXT:  # %bb.4: # %entry
-; AIX-NEXT:    fmr 1, 0
-; AIX-NEXT:  L..BB3_5: # %entry
-; AIX-NEXT:    cmpdi 4, 0
-; AIX-NEXT:    bc 12, 2, L..BB3_7
-; AIX-NEXT:  # %bb.6: # %entry
-; AIX-NEXT:    fmr 2, 1
-; AIX-NEXT:  L..BB3_7: # %entry
-; AIX-NEXT:    xxlxor 1, 1, 1
-; AIX-NEXT:    fcmpu 0, 0, 1
-; AIX-NEXT:    bc 12, 2, L..BB3_9
-; AIX-NEXT:  # %bb.8: # %entry
-; AIX-NEXT:    fmr 2, 0
-; AIX-NEXT:  L..BB3_9: # %entry
-; AIX-NEXT:    fmr 1, 2
+; AIX-NEXT:    ld 3, L..C3(2) # %const.0
+; AIX-NEXT:    lfs 1, 0(3)
 ; AIX-NEXT:    blr
 entry:
   %m = call double @llvm.maximum.f64(double %a, double %b)