Index: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -2337,6 +2337,37 @@
       return II;
     break;
   }
+  case Intrinsic::x86_avx512_mask_cmp_pd_128:
+  case Intrinsic::x86_avx512_mask_cmp_pd_256:
+  case Intrinsic::x86_avx512_mask_cmp_pd_512:
+  case Intrinsic::x86_avx512_mask_cmp_ps_128:
+  case Intrinsic::x86_avx512_mask_cmp_ps_256:
+  case Intrinsic::x86_avx512_mask_cmp_ps_512: {
+    // Folding cmp(sub(a,b),0) -> cmp(a,b) and cmp(0,sub(a,b)) -> cmp(b,a)
+    Value *Arg0 = II->getArgOperand(0);
+    Value *Arg1 = II->getArgOperand(1);
+    bool Arg0IsZero = match(Arg0, m_Zero());
+    if (Arg0IsZero)
+      std::swap(Arg0, Arg1);
+    Value *A, *B;
+    // This fold requires only the NINF(not +/- inf) since inf minus
+    // inf is nan.
+    // NSZ(No Signed Zeros) is not needed because zeros of any sign are
+    // equal for both compares.
+    // NNAN is not needed because nans compare the same for both compares.
+    // The compare intrinsic uses the above assumptions and therefore
+    // doesn't require additional flags.
+    if ((match(Arg0, m_OneUse(m_FSub(m_Value(A), m_Value(B)))) &&
+         match(Arg1, m_Zero()) &&
+         cast<Instruction>(Arg0)->getFastMathFlags().noInfs())) {
+      if (Arg0IsZero)
+        std::swap(A, B);
+      II->setArgOperand(0, A);
+      II->setArgOperand(1, B);
+      return II;
+    }
+    break;
+  }
 
   case Intrinsic::x86_avx512_mask_add_ps_512:
   case Intrinsic::x86_avx512_mask_div_ps_512:
Index: llvm/trunk/test/Transforms/InstCombine/X86FsubCmpCombine.ll
===================================================================
--- llvm/trunk/test/Transforms/InstCombine/X86FsubCmpCombine.ll
+++ llvm/trunk/test/Transforms/InstCombine/X86FsubCmpCombine.ll
@@ -0,0 +1,181 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; The test checks the folding of cmp(sub(a,b),0) into cmp(a,b).
+
+define i8 @sub_compare_foldingPD128_safe(<2 x double> %a, <2 x double> %b){
+; CHECK-LABEL: @sub_compare_foldingPD128_safe(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[SUB_SAFE:%.*]] = fsub <2 x double> [[A:%.*]], [[B:%.*]]
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call i8 @llvm.x86.avx512.mask.cmp.pd.128(<2 x double> [[SUB_SAFE]], <2 x double> zeroinitializer, i32 5, i8 -1)
+; CHECK-NEXT:    ret i8 [[TMP0]]
+;
+entry:
+  %sub.safe = fsub <2 x double> %a, %b
+  %0 = tail call i8 @llvm.x86.avx512.mask.cmp.pd.128(<2 x double> %sub.safe , <2 x double> zeroinitializer, i32 5, i8 -1)
+  ret i8 %0
+}
+
+
+define i8 @sub_compare_foldingPD128(<2 x double> %a, <2 x double> %b){
+; CHECK-LABEL: @sub_compare_foldingPD128(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call i8 @llvm.x86.avx512.mask.cmp.pd.128(<2 x double> [[A:%.*]], <2 x double> [[B:%.*]], i32 5, i8 -1)
+; CHECK-NEXT:    ret i8 [[TMP0]]
+;
+entry:
+  %sub.i = fsub ninf <2 x double> %a, %b
+  %0 = tail call i8 @llvm.x86.avx512.mask.cmp.pd.128(<2 x double> %sub.i , <2 x double> zeroinitializer, i32 5, i8 -1)
+  ret i8 %0
+}
+
+
+define i8 @sub_compare_foldingPD256(<4 x double> %a, <4 x double> %b){
+; CHECK-LABEL: @sub_compare_foldingPD256(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call i8 @llvm.x86.avx512.mask.cmp.pd.256(<4 x double> [[A:%.*]], <4 x double> [[B:%.*]], i32 5, i8 -1)
+; CHECK-NEXT:    ret i8 [[TMP0]]
+;
+entry:
+  %sub.i1 = fsub ninf <4 x double> %a, %b
+  %0 = tail call i8 @llvm.x86.avx512.mask.cmp.pd.256(<4 x double> %sub.i1, <4 x double> zeroinitializer, i32 5, i8 -1)
+  ret i8 %0
+}
+
+
+define i8 @sub_compare_foldingPD512(<8 x double> %a, <8 x double> %b){
+; CHECK-LABEL: @sub_compare_foldingPD512(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call i8 @llvm.x86.avx512.mask.cmp.pd.512(<8 x double> [[A:%.*]], <8 x double> [[B:%.*]], i32 11, i8 -1, i32 4)
+; CHECK-NEXT:    ret i8 [[TMP0]]
+;
+entry:
+  %sub.i2 = fsub ninf <8 x double> %a, %b
+  %0 = tail call i8 @llvm.x86.avx512.mask.cmp.pd.512(<8 x double> %sub.i2, <8 x double> zeroinitializer, i32 11, i8 -1, i32 4)
+  ret i8 %0
+}
+
+
+define i8 @sub_compare_foldingPS128(<4 x float> %a, <4 x float> %b){
+; CHECK-LABEL: @sub_compare_foldingPS128(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call i8 @llvm.x86.avx512.mask.cmp.ps.128(<4 x float> [[A:%.*]], <4 x float> [[B:%.*]], i32 12, i8 -1)
+; CHECK-NEXT:    ret i8 [[TMP0]]
+;
+entry:
+  %sub.i3 = fsub ninf <4 x float> %a, %b
+  %0 = tail call i8 @llvm.x86.avx512.mask.cmp.ps.128(<4 x float> %sub.i3, <4 x float> zeroinitializer, i32 12, i8 -1)
+  ret i8 %0
+}
+
+
+define i8 @sub_compare_foldingPS256(<8 x float> %a, <8 x float> %b){
+; CHECK-LABEL: @sub_compare_foldingPS256(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call i8 @llvm.x86.avx512.mask.cmp.ps.256(<8 x float> [[A:%.*]], <8 x float> [[B:%.*]], i32 5, i8 -1)
+; CHECK-NEXT:    ret i8 [[TMP0]]
+;
+entry:
+  %sub.i4 = fsub ninf <8 x float> %a, %b
+  %0 = tail call i8 @llvm.x86.avx512.mask.cmp.ps.256(<8 x float> %sub.i4, <8 x float> zeroinitializer, i32 5, i8 -1)
+  ret i8 %0
+}
+
+
+define i16 @sub_compare_foldingPS512(<16 x float> %a, <16 x float> %b){
+; CHECK-LABEL: @sub_compare_foldingPS512(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call i16 @llvm.x86.avx512.mask.cmp.ps.512(<16 x float> [[A:%.*]], <16 x float> [[B:%.*]], i32 11, i16 -1, i32 4)
+; CHECK-NEXT:    ret i16 [[TMP0]]
+;
+entry:
+  %sub.i5 = fsub ninf <16 x float> %a, %b
+  %0 = tail call i16 @llvm.x86.avx512.mask.cmp.ps.512(<16 x float> %sub.i5, <16 x float> zeroinitializer, i32 11, i16 -1, i32 4)
+  ret i16 %0
+}
+
+
+
+define i8 @sub_compare_folding_swapPD128(<2 x double> %a, <2 x double> %b){
+; CHECK-LABEL: @sub_compare_folding_swapPD128(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call i8 @llvm.x86.avx512.mask.cmp.pd.128(<2 x double> [[B:%.*]], <2 x double> [[A:%.*]], i32 5, i8 -1)
+; CHECK-NEXT:    ret i8 [[TMP0]]
+;
+entry:
+  %sub.i = fsub ninf <2 x double> %a, %b
+  %0 = tail call i8 @llvm.x86.avx512.mask.cmp.pd.128(<2 x double> zeroinitializer, <2 x double> %sub.i, i32 5, i8 -1)
+  ret i8 %0
+}
+
+
+define i8 @sub_compare_folding_swapPD256(<4 x double> %a, <4 x double> %b){
+; CHECK-LABEL: @sub_compare_folding_swapPD256(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call i8 @llvm.x86.avx512.mask.cmp.pd.256(<4 x double> [[B:%.*]], <4 x double> [[A:%.*]], i32 5, i8 -1)
+; CHECK-NEXT:    ret i8 [[TMP0]]
+;
+entry:
+  %sub.i = fsub ninf <4 x double> %a, %b
+  %0 = tail call i8 @llvm.x86.avx512.mask.cmp.pd.256(<4 x double> zeroinitializer, <4 x double> %sub.i, i32 5, i8 -1)
+  ret i8 %0
+}
+
+
+define i8 @sub_compare_folding_swapPD512(<8 x double> %a, <8 x double> %b){
+; CHECK-LABEL: @sub_compare_folding_swapPD512(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call i8 @llvm.x86.avx512.mask.cmp.pd.512(<8 x double> [[B:%.*]], <8 x double> [[A:%.*]], i32 11, i8 -1, i32 4)
+; CHECK-NEXT:    ret i8 [[TMP0]]
+;
+entry:
+  %sub.i = fsub ninf <8 x double> %a, %b
+  %0 = tail call i8 @llvm.x86.avx512.mask.cmp.pd.512(<8 x double> zeroinitializer, <8 x double> %sub.i, i32 11, i8 -1, i32 4)
+  ret i8 %0
+}
+
+
+define i8 @sub_compare_folding_swapPS128(<4 x float> %a, <4 x float> %b){
+; CHECK-LABEL: @sub_compare_folding_swapPS128(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call i8 @llvm.x86.avx512.mask.cmp.ps.128(<4 x float> [[B:%.*]], <4 x float> [[A:%.*]], i32 12, i8 -1)
+; CHECK-NEXT:    ret i8 [[TMP0]]
+;
+entry:
+  %sub.i = fsub ninf <4 x float> %a, %b
+  %0 = tail call i8 @llvm.x86.avx512.mask.cmp.ps.128(<4 x float> zeroinitializer, <4 x float> %sub.i, i32 12, i8 -1)
+  ret i8 %0
+}
+
+
+define i8 @sub_compare_folding_swapPS256(<8 x float> %a, <8 x float> %b){
+; CHECK-LABEL: @sub_compare_folding_swapPS256(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call i8 @llvm.x86.avx512.mask.cmp.ps.256(<8 x float> [[B:%.*]], <8 x float> [[A:%.*]], i32 5, i8 -1)
+; CHECK-NEXT:    ret i8 [[TMP0]]
+;
+entry:
+  %sub.i = fsub ninf <8 x float> %a, %b
+  %0 = tail call i8 @llvm.x86.avx512.mask.cmp.ps.256(<8 x float> zeroinitializer, <8 x float> %sub.i, i32 5, i8 -1)
+  ret i8 %0
+}
+
+
+define i16 @sub_compare_folding_swapPS512(<16 x float> %a, <16 x float> %b){
+; CHECK-LABEL: @sub_compare_folding_swapPS512(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call i16 @llvm.x86.avx512.mask.cmp.ps.512(<16 x float> [[B:%.*]], <16 x float> [[A:%.*]], i32 11, i16 -1, i32 4)
+; CHECK-NEXT:    ret i16 [[TMP0]]
+;
+entry:
+  %sub.i = fsub ninf <16 x float> %a, %b
+  %0 = tail call i16 @llvm.x86.avx512.mask.cmp.ps.512(<16 x float> zeroinitializer, <16 x float> %sub.i, i32 11, i16 -1, i32 4)
+  ret i16 %0
+}
+
+declare i8 @llvm.x86.avx512.mask.cmp.pd.128(<2 x double>, <2 x double>, i32, i8)
+declare i8 @llvm.x86.avx512.mask.cmp.pd.256(<4 x double>, <4 x double>, i32, i8)
+declare i8 @llvm.x86.avx512.mask.cmp.pd.512(<8 x double>, <8 x double>, i32, i8, i32)
+declare i8 @llvm.x86.avx512.mask.cmp.ps.128(<4 x float>, <4 x float>, i32, i8)
+declare i8 @llvm.x86.avx512.mask.cmp.ps.256(<8 x float>, <8 x float>, i32, i8)
+declare i16 @llvm.x86.avx512.mask.cmp.ps.512(<16 x float>, <16 x float>, i32, i16, i32)