Index: include/llvm/Transforms/Utils/BuildLibCalls.h
===================================================================
--- include/llvm/Transforms/Utils/BuildLibCalls.h
+++ include/llvm/Transforms/Utils/BuildLibCalls.h
@@ -15,6 +15,7 @@
 #ifndef LLVM_TRANSFORMS_UTILS_BUILDLIBCALLS_H
 #define LLVM_TRANSFORMS_UTILS_BUILDLIBCALLS_H
 
+#include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/IR/IRBuilder.h"
 
 namespace llvm {
@@ -29,6 +30,12 @@
   /// Returns true if any attributes were set and false otherwise.
   bool inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI);
 
+  /// Check whether the overloaded unary floating point function
+  /// corresponding to \a Ty is available.
+  bool hasUnaryFloatFn(const TargetLibraryInfo *TLI, Type *Ty,
+                       LibFunc DoubleFn, LibFunc FloatFn,
+                       LibFunc LongDoubleFn);
+
   /// Return V if it is an i8*, otherwise cast it to i8*.
   Value *castToCStr(Value *V, IRBuilder<> &B);
 
Index: lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -33,6 +33,7 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/KnownBits.h"
 #include "llvm/Transforms/InstCombine/InstCombineWorklist.h"
+#include "llvm/Transforms/Utils/BuildLibCalls.h"
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
@@ -1468,6 +1469,23 @@
     }
   }
 
+  // sin(a) / cos(a) -> tan(a)
+  if (AllowReassociate) {
+    Value *A;
+    if (match(Op0, m_Intrinsic<Intrinsic::sin>(m_Value(A))) &&
+        match(Op1, m_Intrinsic<Intrinsic::cos>(m_Specific(A)))) {
+      if (hasUnaryFloatFn(&TLI, I.getType(), LibFunc_tan,
+                          LibFunc_tanf, LibFunc_tanl)) {
+        IRBuilder<> B(&I);
+        IRBuilder<>::FastMathFlagGuard Guard(B);
+        B.setFastMathFlags(I.getFastMathFlags());
+        Value *Tan = emitUnaryFloatFnCall(A, TLI.getName(LibFunc_tan),
+                                          B, I.getFunction()->getAttributes());
+        return replaceInstUsesWith(I, Tan);
+      }
+    }
+  }
+
   Value *LHS;
   Value *RHS;
 
Index: lib/Transforms/Utils/BuildLibCalls.cpp
===================================================================
--- lib/Transforms/Utils/BuildLibCalls.cpp
+++ lib/Transforms/Utils/BuildLibCalls.cpp
@@ -709,6 +709,19 @@
   }
 }
 
+bool llvm::hasUnaryFloatFn(const TargetLibraryInfo *TLI, Type *Ty,
+                           LibFunc DoubleFn, LibFunc FloatFn,
+                           LibFunc LongDoubleFn) {
+  switch (Ty->getTypeID()) {
+  case Type::FloatTyID:
+    return TLI->has(FloatFn);
+  case Type::DoubleTyID:
+    return TLI->has(DoubleFn);
+  default:
+    return TLI->has(LongDoubleFn);
+  }
+}
+
 //- Emit LibCalls ------------------------------------------------------------//
 
 Value *llvm::castToCStr(Value *V, IRBuilder<> &B) {
Index: lib/Transforms/Utils/SimplifyLibCalls.cpp
===================================================================
--- lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -104,21 +104,6 @@
   });
 }
 
-/// \brief Check whether the overloaded unary floating point function
-/// corresponding to \a Ty is available.
-static bool hasUnaryFloatFn(const TargetLibraryInfo *TLI, Type *Ty,
-                            LibFunc DoubleFn, LibFunc FloatFn,
-                            LibFunc LongDoubleFn) {
-  switch (Ty->getTypeID()) {
-  case Type::FloatTyID:
-    return TLI->has(FloatFn);
-  case Type::DoubleTyID:
-    return TLI->has(DoubleFn);
-  default:
-    return TLI->has(LongDoubleFn);
-  }
-}
-
 //===----------------------------------------------------------------------===//
 // String and Memory Library Call Optimizations
 //===----------------------------------------------------------------------===//
Index: test/Transforms/InstCombine/fdiv.ll
===================================================================
--- test/Transforms/InstCombine/fdiv.ll
+++ test/Transforms/InstCombine/fdiv.ll
@@ -1,3 +1,4 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -S -instcombine < %s | FileCheck %s
 
 define float @test1(float %x) nounwind readnone ssp {
@@ -67,3 +68,96 @@
   %div = fdiv fast float %x.fneg, %y.fneg
   ret float %div
 }
+
+define double @fdiv_sin_cos(double %a) {
+; CHECK-LABEL: @fdiv_sin_cos(
+; CHECK-NEXT:    [[TMP1:%.*]] = call double @llvm.sin.f64(double [[A:%.*]])
+; CHECK-NEXT:    [[TMP2:%.*]] = call double @llvm.cos.f64(double [[A]])
+; CHECK-NEXT:    [[DIV:%.*]] = fdiv double [[TMP1]], [[TMP2]]
+; CHECK-NEXT:    ret double [[DIV]]
+;
+  %1 = call double @llvm.sin.f64(double %a)
+  %2 = call double @llvm.cos.f64(double %a)
+  %div = fdiv double %1, %2
+  ret double %div
+}
+
+define double @fdiv_strict_sin_strict_cos_fast(double %a) {
+; CHECK-LABEL: @fdiv_strict_sin_strict_cos_fast(
+; CHECK-NEXT:    [[TMP1:%.*]] = call double @llvm.sin.f64(double [[A:%.*]])
+; CHECK-NEXT:    [[TMP2:%.*]] = call fast double @llvm.cos.f64(double [[A]])
+; CHECK-NEXT:    [[DIV:%.*]] = fdiv double [[TMP1]], [[TMP2]]
+; CHECK-NEXT:    ret double [[DIV]]
+;
+  %1 = call double @llvm.sin.f64(double %a)
+  %2 = call fast double @llvm.cos.f64(double %a)
+  %div = fdiv double %1, %2
+  ret double %div
+}
+
+define double @fdiv_fast_sin_strict_cos_strict(double %a) {
+; CHECK-LABEL: @fdiv_fast_sin_strict_cos_strict(
+; CHECK-NEXT:    [[TAN:%.*]] = call fast double @tan(double [[A:%.*]])
+; CHECK-NEXT:    ret double [[TAN]]
+;
+  %1 = call double @llvm.sin.f64(double %a)
+  %2 = call double @llvm.cos.f64(double %a)
+  %div = fdiv fast double %1, %2
+  ret double %div
+}
+
+define double @fdiv_fast_sin_fast_cos_strict(double %a) {
+; CHECK-LABEL: @fdiv_fast_sin_fast_cos_strict(
+; CHECK-NEXT:    [[TAN:%.*]] = call fast double @tan(double [[A:%.*]])
+; CHECK-NEXT:    ret double [[TAN]]
+;
+  %1 = call fast double @llvm.sin.f64(double %a)
+  %2 = call double @llvm.cos.f64(double %a)
+  %div = fdiv fast double %1, %2
+  ret double %div
+}
+
+define double @fdiv_sin_cos_fast(double %a) {
+; CHECK-LABEL: @fdiv_sin_cos_fast(
+; CHECK-NEXT:    [[TMP1:%.*]] = call fast double @tan(double [[A:%.*]])
+; CHECK-NEXT:    ret double [[TMP1]]
+;
+  %1 = call fast double @llvm.sin.f64(double %a)
+  %2 = call fast double @llvm.cos.f64(double %a)
+  %div = fdiv fast double %1, %2
+  ret double %div
+}
+
+define float @fdiv_sinf_cosf_fast(float %a) {
+; CHECK-LABEL: @fdiv_sinf_cosf_fast(
+; CHECK-NEXT:    [[TMP1:%.*]] = call fast float @tanf(float [[A:%.*]])
+; CHECK-NEXT:    ret float [[TMP1]]
+;
+  %1 = call fast float @llvm.sin.f32(float %a)
+  %2 = call fast float @llvm.cos.f32(float %a)
+  %div = fdiv fast float %1, %2
+  ret float %div
+}
+
+define fp128 @fdiv_sinfp128_cosfp128_fast(fp128 %a) {
+; CHECK-LABEL: @fdiv_sinfp128_cosfp128_fast(
+; CHECK-NEXT:    [[TMP0:%.*]] = call fast fp128 @tanl(fp128 [[A:%.*]])
+; CHECK-NEXT:    ret fp128 [[TMP0]]
+;
+  %1 = call fast fp128 @llvm.sin.fp128(fp128 %a)
+  %2 = call fast fp128 @llvm.cos.fp128(fp128 %a)
+  %div = fdiv fast fp128 %1, %2
+  ret fp128 %div
+}
+
+declare double @llvm.sin.f64(double)
+declare float @llvm.sin.f32(float)
+declare fp128 @llvm.sin.fp128(fp128)
+
+declare double @llvm.cos.f64(double)
+declare float @llvm.cos.f32(float)
+declare fp128 @llvm.cos.fp128(fp128)
+
+declare double @tan(double)
+declare float @tanf(float)
+declare fp128 @tanl(fp128)