diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 102762dc7937c..3af4ae31ffe8b 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1679,7 +1679,8 @@ bool llvm::canConstantFoldCallTo(const CallBase *Call, const Function *F) {
   case 'l':
     return Name == "log" || Name == "logf" || Name == "logl" ||
            Name == "log2" || Name == "log2f" || Name == "log10" ||
-           Name == "log10f" || Name == "logb" || Name == "logbf";
+           Name == "log10f" || Name == "logb" || Name == "logbf" ||
+           Name == "log1p" || Name == "log1pf";
   case 'n':
     return Name == "nearbyint" || Name == "nearbyintf";
   case 'p':
@@ -2394,6 +2395,11 @@ static Constant *ConstantFoldScalarCall1(StringRef Name,
       if (!APF.isZero() && TLI->has(Func))
         return ConstantFoldFP(logb, APF, Ty);
       break;
+    case LibFunc_log1p:
+    case LibFunc_log1pf:
+      if (APF > APFloat::getOne(APF.getSemantics(), true) && TLI->has(Func))
+        return ConstantFoldFP(log1p, APF, Ty);
+      break;
     case LibFunc_logl:
       return nullptr;
     case LibFunc_nearbyint:
@@ -3588,8 +3594,8 @@ bool llvm::isMathLibCallNoop(const CallBase *Call,
       case LibFunc_acosl:
       case LibFunc_acos:
       case LibFunc_acosf:
-        return !(Op < APFloat(Op.getSemantics(), "-1") ||
-                 Op > APFloat(Op.getSemantics(), "1"));
+        return !(Op < APFloat::getOne(Op.getSemantics(), true) ||
+                 Op > APFloat::getOne(Op.getSemantics()));
 
       case LibFunc_sinh:
       case LibFunc_cosh:
diff --git a/llvm/test/Transforms/InstCombine/log1p.ll b/llvm/test/Transforms/InstCombine/log1p.ll
new file mode 100644
index 0000000000000..81d3cc8a4f7ac
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/log1p.ll
@@ -0,0 +1,275 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+
+define float @log1pf_const() {
+; CHECK-LABEL: define float @log1pf_const() {
+; CHECK-NEXT:    [[R:%.*]] = call float @log1pf(float 7.000000e+00)
+; CHECK-NEXT:    ret float 0x4000A2B240000000
+;
+  %r = call float @log1pf(float 7.000000e+00)
+  ret float %r
+}
+
+define double @log1p_const() {
+; CHECK-LABEL: define double @log1p_const() {
+; CHECK-NEXT:    [[R:%.*]] = call double @log1p(double 7.000000e+00)
+; CHECK-NEXT:    ret double 0x4000A2B23F3BAB73
+;
+  %r = call double @log1p(double 7.000000e+00)
+  ret double %r
+}
+
+define float @log1pf_minus_one() {
+; CHECK-LABEL: define float @log1pf_minus_one() {
+; CHECK-NEXT:    [[R:%.*]] = call float @log1pf(float -1.000000e+00)
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @log1pf(float -1.000000e+00)
+  ret float %r
+}
+
+define double @log1p_minus_one() {
+; CHECK-LABEL: define double @log1p_minus_one() {
+; CHECK-NEXT:    [[R:%.*]] = call double @log1p(double -1.000000e+00)
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @log1p(double -1.000000e+00)
+  ret double %r
+}
+
+define float @log1pf_minus_one_memory_none() {
+; CHECK-LABEL: define float @log1pf_minus_one_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call float @log1pf(float -1.000000e+00) #[[ATTR0:[0-9]+]]
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @log1pf(float -1.000000e+00) readnone
+  ret float %r
+}
+
+define double @log1p_minus_one_memory_none() {
+; CHECK-LABEL: define double @log1p_minus_one_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call double @log1p(double -1.000000e+00) #[[ATTR0]]
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @log1p(double -1.000000e+00) readnone
+  ret double %r
+}
+
+define float @log1pf_zero() {
+; CHECK-LABEL: define float @log1pf_zero() {
+; CHECK-NEXT:    [[R:%.*]] = call float @log1pf(float 0.000000e+00)
+; CHECK-NEXT:    ret float 0.000000e+00
+;
+  %r = call float @log1pf(float 0.000000e+00)
+  ret float %r
+}
+
+define double @log1p_zero() {
+; CHECK-LABEL: define double @log1p_zero() {
+; CHECK-NEXT:    [[R:%.*]] = call double @log1p(double 0.000000e+00)
+; CHECK-NEXT:    ret double 0.000000e+00
+;
+  %r = call double @log1p(double 0.000000e+00)
+  ret double %r
+}
+
+define float @log1pf_neg_zero() {
+; CHECK-LABEL: define float @log1pf_neg_zero() {
+; CHECK-NEXT:    [[R:%.*]] = call float @log1pf(float -0.000000e+00)
+; CHECK-NEXT:    ret float -0.000000e+00
+;
+  %r = call float @log1pf(float -0.000000e+00)
+  ret float %r
+}
+
+define double @log1p_neg_zero() {
+; CHECK-LABEL: define double @log1p_neg_zero() {
+; CHECK-NEXT:    [[R:%.*]] = call double @log1p(double -0.000000e+00)
+; CHECK-NEXT:    ret double -0.000000e+00
+;
+  %r = call double @log1p(double -0.000000e+00)
+  ret double %r
+}
+
+define float @log1pf_neg1() {
+; CHECK-LABEL: define float @log1pf_neg1() {
+; CHECK-NEXT:    [[R:%.*]] = call float @log1pf(float -7.000000e+00)
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @log1pf(float -7.000000e+00)
+  ret float %r
+}
+
+define double @log1p_neg1() {
+; CHECK-LABEL: define double @log1p_neg1() {
+; CHECK-NEXT:    [[R:%.*]] = call double @log1p(double -7.000000e+00)
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @log1p(double -7.000000e+00)
+  ret double %r
+}
+
+define float @log1pf_neg1_memory_none() {
+; CHECK-LABEL: define float @log1pf_neg1_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call float @log1pf(float -7.000000e+00) #[[ATTR0]]
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @log1pf(float -7.000000e+00) readnone
+  ret float %r
+}
+
+define double @log1p_neg1_memory_none() {
+; CHECK-LABEL: define double @log1p_neg1_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call double @log1p(double -7.000000e+00) #[[ATTR0]]
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @log1p(double -7.000000e+00) readnone
+  ret double %r
+}
+
+define float @log1pf_neg2() {
+; CHECK-LABEL: define float @log1pf_neg2() {
+; CHECK-NEXT:    [[R:%.*]] = call float @log1pf(float -5.000000e-01)
+; CHECK-NEXT:    ret float 0xBFE62E4300000000
+;
+  %r = call float @log1pf(float -5.000000e-01)
+  ret float %r
+}
+
+define double @log1p_neg2() {
+; CHECK-LABEL: define double @log1p_neg2() {
+; CHECK-NEXT:    [[R:%.*]] = call double @log1p(double -5.000000e-01)
+; CHECK-NEXT:    ret double 0xBFE62E42FEFA39EF
+;
+  %r = call double @log1p(double -5.000000e-01)
+  ret double %r
+}
+
+define float @log1pf_inf() {
+; CHECK-LABEL: define float @log1pf_inf() {
+; CHECK-NEXT:    [[R:%.*]] = call float @log1pf(float 0x7FF0000000000000)
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @log1pf(float 0x7FF0000000000000)
+  ret float %r
+}
+
+define double @log1p_inf() {
+; CHECK-LABEL: define double @log1p_inf() {
+; CHECK-NEXT:    [[R:%.*]] = call double @log1p(double 0x7FF0000000000000)
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @log1p(double 0x7FF0000000000000)
+  ret double %r
+}
+
+define float @log1pf_inf_memory_none() {
+; CHECK-LABEL: define float @log1pf_inf_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call float @log1pf(float 0x7FF0000000000000) #[[ATTR0]]
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @log1pf(float 0x7FF0000000000000) readnone
+  ret float %r
+}
+
+define double @log1p_inf_memory_none() {
+; CHECK-LABEL: define double @log1p_inf_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call double @log1p(double 0x7FF0000000000000) #[[ATTR0]]
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @log1p(double 0x7FF0000000000000) readnone
+  ret double %r
+}
+
+define float @log1pf_neg_inf() {
+; CHECK-LABEL: define float @log1pf_neg_inf() {
+; CHECK-NEXT:    [[R:%.*]] = call float @log1pf(float 0xFFF0000000000000)
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @log1pf(float 0xFFF0000000000000)
+  ret float %r
+}
+
+define double @log1p_neg_inf() {
+; CHECK-LABEL: define double @log1p_neg_inf() {
+; CHECK-NEXT:    [[R:%.*]] = call double @log1p(double 0xFFF0000000000000)
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @log1p(double 0xFFF0000000000000)
+  ret double %r
+}
+
+define float @log1pf_neg_inf_memory_none() {
+; CHECK-LABEL: define float @log1pf_neg_inf_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call float @log1pf(float 0xFFF0000000000000) #[[ATTR0]]
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @log1pf(float 0xFFF0000000000000) readnone
+  ret float %r
+}
+
+define double @log1p_neg_inf_memory_none() {
+; CHECK-LABEL: define double @log1p_neg_inf_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call double @log1p(double 0xFFF0000000000000) #[[ATTR0]]
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @log1p(double 0xFFF0000000000000) readnone
+  ret double %r
+}
+
+define float @log1pf_nan() {
+; CHECK-LABEL: define float @log1pf_nan() {
+; CHECK-NEXT:    [[R:%.*]] = call float @log1pf(float 0x7FF8000000000000)
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @log1pf(float 0x7FF8000000000000)
+  ret float %r
+}
+
+define double @log1p_nan() {
+; CHECK-LABEL: define double @log1p_nan() {
+; CHECK-NEXT:    [[R:%.*]] = call double @log1p(double 0x7FF8000000000000)
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @log1p(double 0x7FF8000000000000)
+  ret double %r
+}
+
+define float @log1pf_nan_memory_none() {
+; CHECK-LABEL: define float @log1pf_nan_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call float @log1pf(float 0x7FF8000000000000) #[[ATTR0]]
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @log1pf(float 0x7FF8000000000000) readnone
+  ret float %r
+}
+
+define double @log1p_nan_memory_none() {
+; CHECK-LABEL: define double @log1p_nan_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call double @log1p(double 0x7FF8000000000000) #[[ATTR0]]
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @log1p(double 0x7FF8000000000000) readnone
+  ret double %r
+}
+
+define float @log1pf_poison() {
+; CHECK-LABEL: define float @log1pf_poison() {
+; CHECK-NEXT:    [[R:%.*]] = call float @log1pf(float poison)
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @log1pf(float poison)
+  ret float %r
+}
+
+define double @log1p_poison() {
+; CHECK-LABEL: define double @log1p_poison() {
+; CHECK-NEXT:    [[R:%.*]] = call double @log1p(double poison)
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @log1p(double poison)
+  ret double %r
+}
+
+declare float @log1pf(float)
+declare double @log1p(double)