Index: lib/Analysis/ValueTracking.cpp
===================================================================
--- lib/Analysis/ValueTracking.cpp
+++ lib/Analysis/ValueTracking.cpp
@@ -4743,6 +4743,36 @@
                                               Value *TrueVal, Value *FalseVal,
                                               Value *&LHS, Value *&RHS,
                                               unsigned Depth) {
+  if (CmpInst::isFPPredicate(Pred)) {
+    // If an FP compare has a 0.0 operand with a signbit that does not match
+    // a 0.0 operand of the select, then change the compare operand to match.
+    // This is allowed by IEEE-754: comparison ignores the sign of zero.
+    if (match(TrueVal, m_PosZeroFP()) && !match(FalseVal, m_NegZeroFP())) {
+      if (match(CmpLHS, m_NegZeroFP()))
+        CmpLHS = TrueVal;
+      if (match(CmpRHS, m_NegZeroFP()))
+        CmpRHS = TrueVal;
+    }
+    if (match(TrueVal, m_NegZeroFP()) && !match(FalseVal, m_PosZeroFP())) {
+      if (match(CmpLHS, m_PosZeroFP()))
+        CmpLHS = TrueVal;
+      if (match(CmpRHS, m_PosZeroFP()))
+        CmpRHS = TrueVal;
+    }
+    if (match(FalseVal, m_PosZeroFP()) && !match(TrueVal, m_NegZeroFP())) {
+      if (match(CmpLHS, m_NegZeroFP()))
+        CmpLHS = FalseVal;
+      if (match(CmpRHS, m_NegZeroFP()))
+        CmpRHS = FalseVal;
+    }
+    if (match(FalseVal, m_NegZeroFP()) && !match(TrueVal, m_PosZeroFP())) {
+      if (match(CmpLHS, m_PosZeroFP()))
+        CmpLHS = FalseVal;
+      if (match(CmpRHS, m_PosZeroFP()))
+        CmpRHS = FalseVal;
+    }
+  }
+
   LHS = CmpLHS;
   RHS = CmpRHS;
 
Index: test/Transforms/InstCombine/minmax-fp.ll
===================================================================
--- test/Transforms/InstCombine/minmax-fp.ll
+++ test/Transforms/InstCombine/minmax-fp.ll
@@ -57,16 +57,15 @@
   ret double %3
 }
 
-; TODO:
-; From IEEE754: "Comparisons shall ignore the sign of zero (so +0 = −0)."
+; From IEEE754: "Comparisons shall ignore the sign of zero (so +0 = -0)."
 ; So the compare constant may be treated as +0.0, and we sink the fpext.
 
 define double @t6(float %a) {
 ; CHECK-LABEL: @t6(
-; CHECK-NEXT:    [[TMP1:%.*]] = fcmp ult float [[A:%.*]], -0.000000e+00
-; CHECK-NEXT:    [[TMP2:%.*]] = fpext float [[A]] to double
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP1]], double [[TMP2]], double 0.000000e+00
-; CHECK-NEXT:    ret double [[TMP3]]
+; CHECK-NEXT:    [[DOTINV:%.*]] = fcmp oge float [[A:%.*]], 0.000000e+00
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[DOTINV]], float 0.000000e+00, float [[A]]
+; CHECK-NEXT:    [[TMP2:%.*]] = fpext float [[TMP1]] to double
+; CHECK-NEXT:    ret double [[TMP2]]
 ;
   %1 = fcmp ult float %a, -0.0
   %2 = fpext float %a to double
@@ -74,16 +73,15 @@
   ret double %3
 }
 
-; TODO:
-; From IEEE754: "Comparisons shall ignore the sign of zero (so +0 = −0)."
+; From IEEE754: "Comparisons shall ignore the sign of zero (so +0 = -0)."
 ; So the compare constant may be treated as -0.0, and we sink the fpext.
 
 define double @t7(float %a) {
 ; CHECK-LABEL: @t7(
-; CHECK-NEXT:    [[TMP1:%.*]] = fcmp ult float [[A:%.*]], 0.000000e+00
-; CHECK-NEXT:    [[TMP2:%.*]] = fpext float [[A]] to double
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP1]], double [[TMP2]], double -0.000000e+00
-; CHECK-NEXT:    ret double [[TMP3]]
+; CHECK-NEXT:    [[DOTINV:%.*]] = fcmp oge float [[A:%.*]], -0.000000e+00
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[DOTINV]], float -0.000000e+00, float [[A]]
+; CHECK-NEXT:    [[TMP2:%.*]] = fpext float [[TMP1]] to double
+; CHECK-NEXT:    ret double [[TMP2]]
 ;
   %1 = fcmp ult float %a, 0.0
   %2 = fpext float %a to double
@@ -91,15 +89,12 @@
   ret double %3
 }
 
-; TODO:
 ; min(min(x, 0.0), 0.0) --> min(x, 0.0)
 
 define float @fmin_fmin_zero_mismatch(float %x) {
 ; CHECK-LABEL: @fmin_fmin_zero_mismatch(
-; CHECK-NEXT:    [[CMP1:%.*]] = fcmp olt float [[X:%.*]], -0.000000e+00
-; CHECK-NEXT:    [[MIN1:%.*]] = select i1 [[CMP1]], float [[X]], float 0.000000e+00
-; CHECK-NEXT:    [[CMP2:%.*]] = fcmp olt float [[MIN1]], 0.000000e+00
-; CHECK-NEXT:    [[MIN2:%.*]] = select i1 [[CMP2]], float [[MIN1]], float 0.000000e+00
+; CHECK-NEXT:    [[TMP1:%.*]] = fcmp olt float [[X:%.*]], 0.000000e+00
+; CHECK-NEXT:    [[MIN2:%.*]] = select i1 [[TMP1]], float [[X]], float 0.000000e+00
 ; CHECK-NEXT:    ret float [[MIN2]]
 ;
   %cmp1 = fcmp olt float %x, -0.0
@@ -109,16 +104,13 @@
   ret float %min2
 }
 
-; TODO:
 ; max(max(x, -0.0), -0.0) --> max(x, -0.0)
 
 define float @fmax_fmax_zero_mismatch(float %x) {
 ; CHECK-LABEL: @fmax_fmax_zero_mismatch(
-; CHECK-NEXT:    [[CMP1:%.*]] = fcmp ogt float [[X:%.*]], 0.000000e+00
-; CHECK-NEXT:    [[MAX1:%.*]] = select i1 [[CMP1]], float [[X]], float -0.000000e+00
-; CHECK-NEXT:    [[CMP2:%.*]] = fcmp olt float [[MAX1]], 0.000000e+00
-; CHECK-NEXT:    [[MAX2:%.*]] = select i1 [[CMP2]], float -0.000000e+00, float [[MAX1]]
-; CHECK-NEXT:    ret float [[MAX2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = fcmp ogt float [[X:%.*]], -0.000000e+00
+; CHECK-NEXT:    [[MAX11:%.*]] = select i1 [[TMP1]], float [[X]], float -0.000000e+00
+; CHECK-NEXT:    ret float [[MAX11]]
 ;
   %cmp1 = fcmp ogt float %x, 0.0
   %max1 = select i1 %cmp1, float %x, float -0.0
Index: unittests/Analysis/ValueTrackingTest.cpp
===================================================================
--- unittests/Analysis/ValueTrackingTest.cpp
+++ unittests/Analysis/ValueTrackingTest.cpp
@@ -156,8 +156,8 @@
       "  %A = select i1 %1, float 0.0, float %a\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMINNUM, SPNB_RETURNS_NAN, true});
 }
 
 TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero2) {
@@ -167,8 +167,8 @@
       "  %A = select i1 %1, float 0.0, float %a\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMINNUM, SPNB_RETURNS_NAN, false});
 }
 
 TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero3) {
@@ -178,8 +178,8 @@
       "  %A = select i1 %1, float -0.0, float %a\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMINNUM, SPNB_RETURNS_NAN, true});
 }
 
 TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero4) {
@@ -189,8 +189,8 @@
       "  %A = select i1 %1, float -0.0, float %a\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMINNUM, SPNB_RETURNS_NAN, false});
 }
 
 TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero5) {
@@ -200,8 +200,8 @@
       "  %A = select i1 %1, float %a, float 0.0\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMINNUM, SPNB_RETURNS_OTHER, false});
 }
 
 TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero6) {
@@ -211,8 +211,8 @@
       "  %A = select i1 %1, float %a, float 0.0\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMINNUM, SPNB_RETURNS_OTHER, true});
 }
 
 TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero7) {
@@ -222,8 +222,8 @@
       "  %A = select i1 %1, float %a, float -0.0\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMINNUM, SPNB_RETURNS_OTHER, false});
 }
 
 TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero8) {
@@ -233,8 +233,8 @@
       "  %A = select i1 %1, float %a, float -0.0\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMINNUM, SPNB_RETURNS_OTHER, true});
 }
 
 TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero1) {
@@ -244,8 +244,8 @@
       "  %A = select i1 %1, float 0.0, float %a\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMAXNUM, SPNB_RETURNS_NAN, true});
 }
 
 TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero2) {
@@ -255,8 +255,8 @@
       "  %A = select i1 %1, float 0.0, float %a\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMAXNUM, SPNB_RETURNS_NAN, false});
 }
 
 TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero3) {
@@ -266,8 +266,8 @@
       "  %A = select i1 %1, float -0.0, float %a\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMAXNUM, SPNB_RETURNS_NAN, true});
 }
 
 TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero4) {
@@ -277,8 +277,8 @@
       "  %A = select i1 %1, float -0.0, float %a\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMAXNUM, SPNB_RETURNS_NAN, false});
 }
 
 TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero5) {
@@ -288,8 +288,8 @@
       "  %A = select i1 %1, float %a, float 0.0\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMAXNUM, SPNB_RETURNS_OTHER, false});
 }
 
 TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero6) {
@@ -299,8 +299,8 @@
       "  %A = select i1 %1, float %a, float 0.0\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMAXNUM, SPNB_RETURNS_OTHER, true});
 }
 
 TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero7) {
@@ -310,8 +310,8 @@
       "  %A = select i1 %1, float %a, float -0.0\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMAXNUM, SPNB_RETURNS_OTHER, false});
 }
 
 TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero8) {
@@ -321,8 +321,8 @@
       "  %A = select i1 %1, float %a, float -0.0\n"
       "  ret float %A\n"
       "}\n");
-  // FIXME: The sign of zero doesn't matter in fcmp.
-  expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+  // The sign of zero doesn't matter in fcmp.
+  expectPattern({SPF_FMAXNUM, SPNB_RETURNS_OTHER, true});
 }
 
 TEST_F(MatchSelectPatternTest, VectorFMinimum) {