Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -4472,6 +4472,13 @@
     break;
   }
   case Instruction::FMul: {
+    // X * X is always non-negative or a NaN.
+    if (Op->getOperand(0) == Op->getOperand(1))
+      Known.knownNot(fcNegative);
+
+    if ((InterestedClasses & fcNan) != fcNan)
+      break;
+
     KnownFPClass KnownLHS, KnownRHS;
     computeKnownFPClass(Op->getOperand(1), DemandedElts,
                         fcNan | fcInf | fcZero | fcSubnormal, KnownRHS,
Index: llvm/test/Transforms/Attributor/nofpclass-nan-fmul.ll
===================================================================
--- llvm/test/Transforms/Attributor/nofpclass-nan-fmul.ll
+++ llvm/test/Transforms/Attributor/nofpclass-nan-fmul.ll
@@ -164,6 +164,36 @@
   ret float %fmul
 }
 
+define float @ret_fmul_square(float %arg) #0 {
+; CHECK-LABEL: define nofpclass(ninf nzero nsub nnorm) float @ret_fmul_square
+; CHECK-SAME: (float [[ARG:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT:    [[FMUL:%.*]] = fmul float [[ARG]], [[ARG]]
+; CHECK-NEXT:    ret float [[FMUL]]
+;
+  %fmul = fmul float %arg, %arg
+  ret float %fmul
+}
+
+define float @ret_fmul_square_nnan(float nofpclass(nan) %arg) #0 {
+; CHECK-LABEL: define nofpclass(ninf nzero nsub nnorm) float @ret_fmul_square_nnan
+; CHECK-SAME: (float nofpclass(nan) [[ARG:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT:    [[FMUL:%.*]] = fmul float [[ARG]], [[ARG]]
+; CHECK-NEXT:    ret float [[FMUL]]
+;
+  %fmul = fmul float %arg, %arg
+  ret float %fmul
+}
+
+define float @ret_fmul_square_nnan_nzero(float nofpclass(nan zero) %arg) #0 {
+; CHECK-LABEL: define nofpclass(nan ninf nzero nsub nnorm) float @ret_fmul_square_nnan_nzero
+; CHECK-SAME: (float nofpclass(nan zero) [[ARG:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT:    [[FMUL:%.*]] = fmul float [[ARG]], [[ARG]]
+; CHECK-NEXT:    ret float [[FMUL]]
+;
+  %fmul = fmul float %arg, %arg
+  ret float %fmul
+}
+
 attributes #0 = { "denormal-fp-math"="ieee,ieee" }
 attributes #1 = { "denormal-fp-math"="ieee,preserve-sign" }
 attributes #2 = { "denormal-fp-math"="ieee,positive-zero" }
Index: llvm/unittests/Analysis/ValueTrackingTest.cpp
===================================================================
--- llvm/unittests/Analysis/ValueTrackingTest.cpp
+++ llvm/unittests/Analysis/ValueTrackingTest.cpp
@@ -1580,11 +1580,11 @@
 
 TEST_F(ComputeKnownFPClassTest, FMul) {
   parseAssembly(
-      "define float @test(float nofpclass(nan inf) %nnan.ninf, float nofpclass(nan) %nnan, float nofpclass(qnan) %no.qnan, float %unknown) {\n"
-      "  %A = fmul float %nnan.ninf, %nnan.ninf"
-      "  %A2 = fmul float %nnan.ninf, %nnan"
-      "  %A3 = fmul float %nnan, %nnan.ninf"
-      "  %A4 = fmul float %nnan.ninf, %no.qnan"
+      "define float @test(float nofpclass(nan inf) %nnan.ninf0, float nofpclass(nan inf) %nnan.ninf1, float nofpclass(nan) %nnan, float nofpclass(qnan) %no.qnan, float %unknown) {\n"
+      "  %A = fmul float %nnan.ninf0, %nnan.ninf1"
+      "  %A2 = fmul float %nnan.ninf0, %nnan"
+      "  %A3 = fmul float %nnan, %nnan.ninf0"
+      "  %A4 = fmul float %nnan.ninf0, %no.qnan"
       "  %A5 = fmul float %nnan, %nnan"
       "  ret float %A\n"
       "}\n");
@@ -1592,23 +1592,23 @@
   expectKnownFPClass(fcAllFlags, std::nullopt, A2);
   expectKnownFPClass(fcAllFlags, std::nullopt, A3);
   expectKnownFPClass(fcAllFlags, std::nullopt, A4);
-  expectKnownFPClass(fcAllFlags, std::nullopt, A5);
+  expectKnownFPClass(fcPositive | fcNan, std::nullopt, A5);
 }
 
 TEST_F(ComputeKnownFPClassTest, FMulNoZero) {
   parseAssembly(
-      "define float @test(float nofpclass(zero) %no.zero, float nofpclass(zero nan) %no.zero.nan, float nofpclass(nzero nan) %no.negzero.nan, float nofpclass(pzero nan) %no.poszero.nan, float nofpclass(inf nan) %no.inf.nan, float nofpclass(inf) %no.inf, float nofpclass(nan) %no.nan) {\n"
-      "  %A = fmul float %no.zero.nan, %no.zero.nan"
+      "define float @test(float nofpclass(zero) %no.zero, float nofpclass(zero nan) %no.zero.nan0, float nofpclass(zero nan) %no.zero.nan1, float nofpclass(nzero nan) %no.negzero.nan, float nofpclass(pzero nan) %no.poszero.nan, float nofpclass(inf nan) %no.inf.nan, float nofpclass(inf) %no.inf, float nofpclass(nan) %no.nan) {\n"
+      "  %A = fmul float %no.zero.nan0, %no.zero.nan1"
       "  %A2 = fmul float %no.zero, %no.zero"
-      "  %A3 = fmul float %no.poszero.nan, %no.zero.nan"
+      "  %A3 = fmul float %no.poszero.nan, %no.zero.nan0"
       "  %A4 = fmul float %no.nan, %no.zero"
       "  %A5 = fmul float %no.zero, %no.inf"
-      "  %A6 = fmul float %no.zero.nan, %no.nan"
-      "  %A7 = fmul float %no.nan, %no.zero.nan"
+      "  %A6 = fmul float %no.zero.nan0, %no.nan"
+      "  %A7 = fmul float %no.nan, %no.zero.nan0"
       "  ret float %A\n"
       "}\n");
   expectKnownFPClass(fcFinite | fcInf, std::nullopt, A);
-  expectKnownFPClass(fcAllFlags, std::nullopt, A2);
+  expectKnownFPClass(fcPositive | fcNan, std::nullopt, A2);
   expectKnownFPClass(fcAllFlags, std::nullopt, A3);
   expectKnownFPClass(fcAllFlags, std::nullopt, A4);
   expectKnownFPClass(fcAllFlags, std::nullopt, A5);