diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -1563,9 +1563,16 @@
     return emitUnaryFloatFnCall(Expo, TLI, LibFunc_exp10, LibFunc_exp10f,
                                 LibFunc_exp10l, B, Attrs);
 
-  // pow(n, x) -> exp2(log2(n) * x)
-  if (Pow->hasApproxFunc() && Pow->hasNoNaNs() && Pow->hasNoInfs() &&
-      BaseF->isFiniteNonZero() && !BaseF->isNegative()) {
+  // pow(x, y) -> exp2(log2(x) * y)
+  // We can do this transformation for any positive finite n except 1.0, because
+  // pow has this behaviour:
+  //   If x is +1, the result is 1.0 (even if y is a NaN).
+  // which is hard to preserve if y might be infinite or NaN.
+  if (Pow->hasApproxFunc() && Pow->hasNoNaNs() && BaseF->isFiniteNonZero() &&
+      !BaseF->isNegative()) {
+    assert(!match(Base, m_FPOne()) &&
+           "pow(1.0, y) should have been simplified earlier!");
+
     Value *Log = nullptr;
     if (Ty->isFloatTy())
       Log = ConstantFP::get(Ty, std::log2(BaseF->convertToFloat()));
diff --git a/llvm/test/Transforms/InstCombine/pow-exp.ll b/llvm/test/Transforms/InstCombine/pow-exp.ll
--- a/llvm/test/Transforms/InstCombine/pow-exp.ll
+++ b/llvm/test/Transforms/InstCombine/pow-exp.ll
@@ -400,8 +400,9 @@
 
 define double @pow_ok_base_no_ninf(double %e) {
 ; CHECK-LABEL: @pow_ok_base_no_ninf(
-; CHECK-NEXT:    [[CALL:%.*]] = tail call nnan afn double @pow(double 0x3FE6666666666666, double [[E:%.*]])
-; CHECK-NEXT:    ret double [[CALL]]
+; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan afn double [[E:%.*]], 0xBFE0776{{.*}}
+; CHECK-NEXT:    [[EXP2:%.*]] = call nnan afn double @exp2(double [[MUL]])
+; CHECK-NEXT:    ret double [[EXP2]]
 ;
   %call = tail call afn nnan double @pow(double 0x3FE6666666666666, double %e)
   ret double %call