Index: lib/Transforms/Utils/SimplifyLibCalls.cpp
===================================================================
--- lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -1181,11 +1181,6 @@
 
 /// Use square root in place of pow(x, +/-0.5).
 Value *LibCallSimplifier::replacePowWithSqrt(CallInst *Pow, IRBuilder<> &B) {
-  // TODO: There is some subset of 'fast' under which these transforms should
-  // be allowed.
-  if (!Pow->isFast())
-    return nullptr;
-
   Value *Sqrt, *Base = Pow->getArgOperand(0), *Expo = Pow->getArgOperand(1);
   Type *Ty = Pow->getType();
 
@@ -1194,6 +1189,10 @@
       (!ExpoF->isExactlyValue(0.5) && !ExpoF->isExactlyValue(-0.5)))
     return nullptr;
 
+  if (ExpoF->isExactlyValue(-0.5) &&
+      (!Pow->hasNoSignedZeros() || !Pow->hasNoInfs()))
+    return nullptr;
+
   // If errno is never set, then use the intrinsic for sqrt().
   if (Pow->hasFnAttr(Attribute::ReadNone)) {
     Function *SqrtFn = Intrinsic::getDeclaration(Pow->getModule(),
@@ -1214,6 +1213,24 @@
   if (ExpoF->isNegative())
     Sqrt = B.CreateFDiv(ConstantFP::get(Ty, 1.0), Sqrt, "reciprocal");
 
+  // Deal with x == -0. We expand pow(x, 0.5/-0.5) to fabs(sqrt(x)|1/sqrt(x)).
+  // This is faster than calling pow(), and still handles -0 correctly.
+  if (!Pow->hasNoSignedZeros()) {
+    Function *FAbsFn =
+        Intrinsic::getDeclaration(Pow->getModule(), Intrinsic::fabs, Ty);
+    Sqrt = B.CreateCall(FAbsFn, Sqrt, "abs");
+  }
+
+  // Deal with x == -infinity. We expand
+  //  * pow(x, 0.5) to (x == -infinity ? +infinity : Sqrt))
+  // This is faster than calling pow(), and still handles negative infinity
+  // correctly.
+  if (!Pow->hasNoInfs()) {
+    Value *NegInf = ConstantFP::getInfinity(Ty, true);
+    Value *PosInf = ConstantFP::getInfinity(Ty);
+    Value *FCmp = B.CreateFCmpOEQ(Base, NegInf, "isinf");
+    Sqrt = B.CreateSelect(FCmp, PosInf, Sqrt);
+  }
   return Sqrt;
 }
 
@@ -1299,28 +1316,6 @@
   if (Value *Sqrt = replacePowWithSqrt(Pow, B))
     return Sqrt;
 
-  // FIXME: Correct the transforms and pull this into replacePowWithSqrt().
-  ConstantFP *ExpoC = dyn_cast<ConstantFP>(Expo);
-  if (ExpoC && ExpoC->isExactlyValue(0.5) &&
-      hasUnaryFloatFn(TLI, Ty, LibFunc_sqrt, LibFunc_sqrtf, LibFunc_sqrtl)) {
-    // Expand pow(x, 0.5) to (x == -infinity ? +infinity : fabs(sqrt(x))).
-    // This is faster than calling pow(), and still handles -0.0 and
-    // negative infinity correctly.
-    // TODO: In finite-only mode, this could be just fabs(sqrt(x)).
-    Value *PosInf = ConstantFP::getInfinity(Ty);
-    Value *NegInf = ConstantFP::getInfinity(Ty, true);
-
-    // TODO: As above, we should lower to the sqrt() intrinsic if the pow() is
-    // an intrinsic, to match errno semantics.
-    Value *Sqrt = emitUnaryFloatFnCall(Base, TLI->getName(LibFunc_sqrt),
-                                       B, Attrs);
-    Function *FAbsFn = Intrinsic::getDeclaration(Module, Intrinsic::fabs, Ty);
-    Value *FAbs = B.CreateCall(FAbsFn, Sqrt, "abs");
-    Value *FCmp = B.CreateFCmpOEQ(Base, NegInf, "isinf");
-    Sqrt = B.CreateSelect(FCmp, PosInf, FAbs);
-    return Sqrt;
-  }
-
   // pow(x, n) -> x * x * x * ...
   const APFloat *ExpoF;
   if (Pow->isFast() && match(Expo, m_APFloat(ExpoF))) {
Index: test/Transforms/InstCombine/pow-1.ll
===================================================================
--- test/Transforms/InstCombine/pow-1.ll
+++ test/Transforms/InstCombine/pow-1.ll
@@ -293,7 +293,7 @@
 declare double @llvm.pow.f64(double %Val, double %Power)
 define double @test_simplify17(double %x) {
 ; ANY-LABEL: @test_simplify17(
-; ANY-NEXT:    [[SQRT:%.*]] = call double @sqrt(double [[X:%.*]]) #2
+; ANY-NEXT:    [[SQRT:%.*]] = call double @llvm.sqrt.f64(double [[X:%.*]])
 ; ANY-NEXT:    [[ABS:%.*]] = call double @llvm.fabs.f64(double [[SQRT]])
 ; ANY-NEXT:    [[ISINF:%.*]] = fcmp oeq double [[X]], 0xFFF0000000000000
 ; ANY-NEXT:    [[TMP1:%.*]] = select i1 [[ISINF]], double 0x7FF0000000000000, double [[ABS]]
Index: test/Transforms/InstCombine/pow-sqrt.ll
===================================================================
--- test/Transforms/InstCombine/pow-sqrt.ll
+++ test/Transforms/InstCombine/pow-sqrt.ll
@@ -19,11 +19,11 @@
 
 define double @pow_intrinsic_half_no_FMF(double %x) {
 ; CHECK-LABEL: @pow_intrinsic_half_no_FMF(
-; CHECK-NEXT:    [[SQRT:%.*]] = call double @sqrt(double [[X:%.*]]) #1
-; CHECK-NEXT:    [[ABS:%.*]] = call double @llvm.fabs.f64(double [[SQRT]])
+; CHECK-NEXT:    [[TMP1:%.*]] = call double @llvm.sqrt.f64(double [[X:%.*]])
+; CHECK-NEXT:    [[ABS:%.*]] = call double @llvm.fabs.f64(double [[TMP1]])
 ; CHECK-NEXT:    [[ISINF:%.*]] = fcmp oeq double [[X]], 0xFFF0000000000000
-; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[ISINF]], double 0x7FF0000000000000, double [[ABS]]
-; CHECK-NEXT:    ret double [[TMP1]]
+; CHECK-NEXT:    [[TMP2:%.*]] = select i1 [[ISINF]], double 0x7FF0000000000000, double [[ABS]]
+; CHECK-NEXT:    ret double [[TMP2]]
 ;
   %pow = call double @llvm.pow.f64(double %x, double 5.0e-01)
   ret double %pow
@@ -43,95 +43,73 @@
   ret double %pow
 }
 
-; FIXME
-
 define <2 x double> @pow_intrinsic_half_approx(<2 x double> %x) {
 ; CHECK-LABEL: @pow_intrinsic_half_approx(
-; CHECK-NEXT:    [[POW:%.*]] = call afn <2 x double> @llvm.pow.v2f64(<2 x double> [[X:%.*]], <2 x double> <double 5.000000e-01, double 5.000000e-01>)
-; CHECK-NEXT:    ret <2 x double> [[POW]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call afn <2 x double> @llvm.sqrt.v2f64(<2 x double> [[X:%.*]])
+; CHECK-NEXT:    [[ABS:%.*]] = call afn <2 x double> @llvm.fabs.v2f64(<2 x double> [[TMP1]])
+; CHECK-NEXT:    [[ISINF:%.*]] = fcmp afn oeq <2 x double> [[X]], <double 0xFFF0000000000000, double 0xFFF0000000000000>
+; CHECK-NEXT:    [[TMP2:%.*]] = select <2 x i1> [[ISINF]], <2 x double> <double 0x7FF0000000000000, double 0x7FF0000000000000>, <2 x double> [[ABS]]
+; CHECK-NEXT:    ret <2 x double> [[TMP2]]
 ;
   %pow = call afn <2 x double> @llvm.pow.v2f64(<2 x double> %x, <2 x double> <double 5.0e-01, double 5.0e-01>)
   ret <2 x double> %pow
 }
 
-; FIXME:
 ; If we can disregard INFs, no need for a select.
-
 define double @pow_libcall_half_ninf(double %x) {
 ; CHECK-LABEL: @pow_libcall_half_ninf(
 ; CHECK-NEXT:    [[SQRT:%.*]] = call ninf double @sqrt(double [[X:%.*]])
 ; CHECK-NEXT:    [[ABS:%.*]] = call ninf double @llvm.fabs.f64(double [[SQRT]])
-; CHECK-NEXT:    [[ISINF:%.*]] = fcmp ninf oeq double [[X]], 0xFFF0000000000000
-; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[ISINF]], double 0x7FF0000000000000, double [[ABS]]
-; CHECK-NEXT:    ret double [[TMP1]]
+; CHECK-NEXT:    ret double [[ABS]]
 ;
   %pow = call ninf double @pow(double %x, double 5.0e-01)
   ret double %pow
 }
 
-; FIXME:
-
 define <2 x double> @pow_intrinsic_half_ninf(<2 x double> %x) {
 ; CHECK-LABEL: @pow_intrinsic_half_ninf(
-; CHECK-NEXT:    [[POW:%.*]] = call ninf <2 x double> @llvm.pow.v2f64(<2 x double> [[X:%.*]], <2 x double> <double 5.000000e-01, double 5.000000e-01>)
-; CHECK-NEXT:    ret <2 x double> [[POW]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call ninf <2 x double> @llvm.sqrt.v2f64(<2 x double> [[X:%.*]])
+; CHECK-NEXT:    [[ABS:%.*]] = call ninf <2 x double> @llvm.fabs.v2f64(<2 x double> [[TMP1]])
+; CHECK-NEXT:    ret <2 x double> [[ABS]]
 ;
   %pow = call ninf <2 x double> @llvm.pow.v2f64(<2 x double> %x, <2 x double> <double 5.0e-01, double 5.0e-01>)
   ret <2 x double> %pow
 }
 
-; FIXME:
-; If we can disregard -0.0, no need for fabs.
-
 define double @pow_libcall_half_nsz(double %x) {
 ; CHECK-LABEL: @pow_libcall_half_nsz(
 ; CHECK-NEXT:    [[SQRT:%.*]] = call nsz double @sqrt(double [[X:%.*]])
-; CHECK-NEXT:    [[ABS:%.*]] = call nsz double @llvm.fabs.f64(double [[SQRT]])
 ; CHECK-NEXT:    [[ISINF:%.*]] = fcmp nsz oeq double [[X]], 0xFFF0000000000000
-; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[ISINF]], double 0x7FF0000000000000, double [[ABS]]
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[ISINF]], double 0x7FF0000000000000, double [[SQRT]]
 ; CHECK-NEXT:    ret double [[TMP1]]
 ;
   %pow = call nsz double @pow(double %x, double 5.0e-01)
   ret double %pow
 }
 
-; FIXME:
-
 define double @pow_intrinsic_half_nsz(double %x) {
 ; CHECK-LABEL: @pow_intrinsic_half_nsz(
-; CHECK-NEXT:    [[SQRT:%.*]] = call nsz double @sqrt(double [[X:%.*]]) #1
-; CHECK-NEXT:    [[ABS:%.*]] = call nsz double @llvm.fabs.f64(double [[SQRT]])
+; CHECK-NEXT:    [[TMP1:%.*]] = call nsz double @llvm.sqrt.f64(double [[X:%.*]])
 ; CHECK-NEXT:    [[ISINF:%.*]] = fcmp nsz oeq double [[X]], 0xFFF0000000000000
-; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[ISINF]], double 0x7FF0000000000000, double [[ABS]]
-; CHECK-NEXT:    ret double [[TMP1]]
+; CHECK-NEXT:    [[TMP2:%.*]] = select i1 [[ISINF]], double 0x7FF0000000000000, double [[TMP1]]
+; CHECK-NEXT:    ret double [[TMP2]]
 ;
   %pow = call nsz double @llvm.pow.f64(double %x, double 5.0e-01)
   ret double %pow
 }
 
-; FIXME:
-; This is just sqrt.
-
 define float @pow_libcall_half_ninf_nsz(float %x) {
 ; CHECK-LABEL: @pow_libcall_half_ninf_nsz(
 ; CHECK-NEXT:    [[SQRTF:%.*]] = call ninf nsz float @sqrtf(float [[X:%.*]])
-; CHECK-NEXT:    [[ABS:%.*]] = call ninf nsz float @llvm.fabs.f32(float [[SQRTF]])
-; CHECK-NEXT:    [[ISINF:%.*]] = fcmp ninf nsz oeq float [[X]], 0xFFF0000000000000
-; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[ISINF]], float 0x7FF0000000000000, float [[ABS]]
-; CHECK-NEXT:    ret float [[TMP1]]
+; CHECK-NEXT:    ret float [[SQRTF]]
 ;
   %pow = call ninf nsz float @powf(float %x, float 5.0e-01)
   ret float %pow
 }
 
-; FIXME:
-
 define double @pow_intrinsic_half_ninf_nsz(double %x) {
 ; CHECK-LABEL: @pow_intrinsic_half_ninf_nsz(
-; CHECK-NEXT:    [[SQRT:%.*]] = call ninf nsz double @sqrt(double [[X:%.*]]) #1
-; CHECK-NEXT:    [[ABS:%.*]] = call ninf nsz double @llvm.fabs.f64(double [[SQRT]])
-; CHECK-NEXT:    [[ISINF:%.*]] = fcmp ninf nsz oeq double [[X]], 0xFFF0000000000000
-; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[ISINF]], double 0x7FF0000000000000, double [[ABS]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call ninf nsz double @llvm.sqrt.f64(double [[X:%.*]])
 ; CHECK-NEXT:    ret double [[TMP1]]
 ;
   %pow = call ninf nsz double @llvm.pow.f64(double %x, double 5.0e-01)
@@ -227,24 +205,23 @@
   ret double %pow
 }
 
-; FIXME:
 ; This is just recip-sqrt.
 
 define double @pow_intrinsic_neghalf_ninf_nsz(double %x) {
 ; CHECK-LABEL: @pow_intrinsic_neghalf_ninf_nsz(
-; CHECK-NEXT:    [[POW:%.*]] = call ninf nsz double @llvm.pow.f64(double [[X:%.*]], double -5.000000e-01)
-; CHECK-NEXT:    ret double [[POW]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call ninf nsz double @llvm.sqrt.f64(double [[X:%.*]])
+; CHECK-NEXT:    [[RECIPROCAL:%.*]] = fdiv ninf nsz double 1.000000e+00, [[TMP1]]
+; CHECK-NEXT:    ret double [[RECIPROCAL]]
 ;
   %pow = call ninf nsz double @llvm.pow.f64(double %x, double -5.0e-01)
   ret double %pow
 }
 
-; FIXME:
-
 define float @pow_libcall_neghalf_ninf_nsz(float %x) {
 ; CHECK-LABEL: @pow_libcall_neghalf_ninf_nsz(
-; CHECK-NEXT:    [[POW:%.*]] = call ninf nsz float @powf(float [[X:%.*]], float -5.000000e-01)
-; CHECK-NEXT:    ret float [[POW]]
+; CHECK-NEXT:    [[SQRTF:%.*]] = call ninf nsz float @sqrtf(float [[X:%.*]])
+; CHECK-NEXT:    [[RECIPROCAL:%.*]] = fdiv ninf nsz float 1.000000e+00, [[SQRTF]]
+; CHECK-NEXT:    ret float [[RECIPROCAL]]
 ;
   %pow = call ninf nsz float @powf(float %x, float -5.0e-01)
   ret float %pow