Index: lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -2032,6 +2032,7 @@
       return II;
     }
 
+    Intrinsic::ID IID = II->getIntrinsicID();
     Value *X, *Y;
     if (match(Arg0, m_FNeg(m_Value(X))) && match(Arg1, m_FNeg(m_Value(Y))) &&
         (Arg0->hasOneUse() || Arg1->hasOneUse())) {
@@ -2039,7 +2040,7 @@
       // min(-X, -Y) --> -(max(X, Y))
       // max(-X, -Y) --> -(min(X, Y))
       Intrinsic::ID NewIID;
-      switch (II->getIntrinsicID()) {
+      switch (IID) {
       case Intrinsic::maxnum:
         NewIID = Intrinsic::minnum;
         break;
@@ -2060,6 +2061,38 @@
       FNeg->copyIRFlags(II);
       return FNeg;
     }
+
+    // m(m(X, C2), C1) -> m(X, C)
+    const APFloat *C1, *C2;
+    if (auto *M0 = dyn_cast<IntrinsicInst>(Arg0)) {
+      if (M0->getIntrinsicID() == IID && match(Arg1, m_APFloat(C1)) &&
+          ((match(M0->getArgOperand(0), m_Value(X)) &&
+            match(M0->getArgOperand(1), m_APFloat(C2))) ||
+           (match(M0->getArgOperand(1), m_Value(X)) &&
+            match(M0->getArgOperand(0), m_APFloat(C2))))) {
+        APFloat Res(0.0);
+        switch (IID) {
+        case Intrinsic::maxnum:
+          Res = maxnum(*C1, *C2);
+          break;
+        case Intrinsic::minnum:
+          Res = minnum(*C1, *C2);
+          break;
+        case Intrinsic::maximum:
+          Res = maximum(*C1, *C2);
+          break;
+        case Intrinsic::minimum:
+          Res = minimum(*C1, *C2);
+          break;
+        default:
+          llvm_unreachable("unexpected intrinsic ID");
+        }
+        Instruction *NewCall = Builder.CreateBinaryIntrinsic(
+            IID, X, ConstantFP::get(Arg0->getType(), Res));
+        return replaceInstUsesWith(*II, NewCall);
+      }
+    }
+
     break;
   }
   case Intrinsic::fmuladd: {
Index: test/Transforms/InstCombine/maximum.ll
===================================================================
--- test/Transforms/InstCombine/maximum.ll
+++ test/Transforms/InstCombine/maximum.ll
@@ -145,6 +145,24 @@
   ret float %y
 }
 
+define float @maximum_f32_1_maximum_val_p0(float %x) {
+; CHECK-LABEL: @maximum_f32_1_maximum_val_p0(
+; CHECK-NEXT: [[RES:%.*]] = call float @llvm.maximum.f32(float %x, float 1.000000e+00)
+; CHECK-NEXT: ret float [[RES]]
+  %y = call float @llvm.maximum.f32(float %x, float 0.0)
+  %z = call float @llvm.maximum.f32(float %y, float 1.0)
+  ret float %z
+}
+
+define float @maximum_f32_1_maximum_p0_val(float %x) {
+; CHECK-LABEL: @maximum_f32_1_maximum_p0_val(
+; CHECK-NEXT: [[RES:%.*]] = call float @llvm.maximum.f32(float %x, float 1.000000e+00)
+; CHECK-NEXT: ret float [[RES]]
+  %y = call float @llvm.maximum.f32(float 0.0, float %x)
+  %z = call float @llvm.maximum.f32(float %y, float 1.0)
+  ret float %z
+}
+
 define float @maximum4(float %x, float %y, float %z, float %w) {
 ; CHECK-LABEL: @maximum4(
 ; CHECK-NEXT:    [[A:%.*]] = call float @llvm.maximum.f32(float [[X:%.*]], float [[Y:%.*]])
Index: test/Transforms/InstCombine/maxnum.ll
===================================================================
--- test/Transforms/InstCombine/maxnum.ll
+++ test/Transforms/InstCombine/maxnum.ll
@@ -145,6 +145,24 @@
   ret float %y
 }
 
+define float @maxnum_f32_1_maxnum_val_p0(float %x) {
+; CHECK-LABEL: @maxnum_f32_1_maxnum_val_p0(
+; CHECK-NEXT: [[RES:%.*]] = call float @llvm.maxnum.f32(float %x, float 1.000000e+00)
+; CHECK-NEXT: ret float [[RES]]
+  %y = call float @llvm.maxnum.f32(float %x, float 0.0)
+  %z = call float @llvm.maxnum.f32(float %y, float 1.0)
+  ret float %z
+}
+
+define float @maxnum_f32_1_maxnum_p0_val(float %x) {
+; CHECK-LABEL: @maxnum_f32_1_maxnum_p0_val(
+; CHECK-NEXT: [[RES:%.*]] = call float @llvm.maxnum.f32(float %x, float 1.000000e+00)
+; CHECK-NEXT: ret float [[RES]]
+  %y = call float @llvm.maxnum.f32(float 0.0, float %x)
+  %z = call float @llvm.maxnum.f32(float %y, float 1.0)
+  ret float %z
+}
+
 define float @maxnum4(float %x, float %y, float %z, float %w) {
 ; CHECK-LABEL: @maxnum4(
 ; CHECK-NEXT:    [[A:%.*]] = call float @llvm.maxnum.f32(float [[X:%.*]], float [[Y:%.*]])
Index: test/Transforms/InstCombine/minimum.ll
===================================================================
--- test/Transforms/InstCombine/minimum.ll
+++ test/Transforms/InstCombine/minimum.ll
@@ -147,6 +147,24 @@
   ret float %y
 }
 
+define float @minimum_f32_1_minimum_val_p0(float %x) {
+; CHECK-LABEL: @minimum_f32_1_minimum_val_p0(
+; CHECK-NEXT: [[RES:%.*]] = call float @llvm.minimum.f32(float %x, float 0.000000e+00)
+; CHECK-NEXT: ret float [[RES]]
+  %y = call float @llvm.minimum.f32(float %x, float 0.0)
+  %z = call float @llvm.minimum.f32(float %y, float 1.0)
+  ret float %z
+}
+
+define float @minimum_f32_1_minimum_p0_val(float %x) {
+; CHECK-LABEL: @minimum_f32_1_minimum_p0_val(
+; CHECK-NEXT: [[RES:%.*]] = call float @llvm.minimum.f32(float %x, float 0.000000e+00)
+; CHECK-NEXT: ret float [[RES]]
+  %y = call float @llvm.minimum.f32(float 0.0, float %x)
+  %z = call float @llvm.minimum.f32(float %y, float 1.0)
+  ret float %z
+}
+
 define float @minimum4(float %x, float %y, float %z, float %w) {
 ; CHECK-LABEL: @minimum4(
 ; CHECK-NEXT:    [[A:%.*]] = call float @llvm.minimum.f32(float [[X:%.*]], float [[Y:%.*]])
Index: test/Transforms/InstCombine/minnum.ll
===================================================================
--- test/Transforms/InstCombine/minnum.ll
+++ test/Transforms/InstCombine/minnum.ll
@@ -147,6 +147,24 @@
   ret float %y
 }
 
+define float @minnum_f32_1_minnum_val_p0(float %x) {
+; CHECK-LABEL: @minnum_f32_1_minnum_val_p0(
+; CHECK-NEXT: [[RES:%.*]] = call float @llvm.minnum.f32(float %x, float 0.000000e+00)
+; CHECK-NEXT: ret float [[RES]]
+  %y = call float @llvm.minnum.f32(float %x, float 0.0)
+  %z = call float @llvm.minnum.f32(float %y, float 1.0)
+  ret float %z
+}
+
+define float @minnum_f32_1_minnum_p0_val(float %x) {
+; CHECK-LABEL: @minnum_f32_1_minnum_p0_val(
+; CHECK-NEXT: [[RES:%.*]] = call float @llvm.minnum.f32(float %x, float 0.000000e+00)
+; CHECK-NEXT: ret float [[RES]]
+  %y = call float @llvm.minnum.f32(float 0.0, float %x)
+  %z = call float @llvm.minnum.f32(float %y, float 1.0)
+  ret float %z
+}
+
 define float @minnum4(float %x, float %y, float %z, float %w) {
 ; CHECK-LABEL: @minnum4(
 ; CHECK-NEXT:    [[A:%.*]] = call float @llvm.minnum.f32(float [[X:%.*]], float [[Y:%.*]])