[InstCombine] Missed optimization in math expression: sin(x) / cos(x) => tan(x)

Summary: This patch enables folding sin(x) / cos(x) -> tan(x), cos(x) / sin(x) -> 1 / tan(x) under -ffast-math flag

Reviewers: hfinkel, spatel

Reviewed By: spatel

Subscribers: andrew.w.kaylor, efriedma, scanon, llvm-commits

Differential Revision: https://reviews.llvm.org/D41286

llvm-svn: 322255

3 files changed, 48 insertions, 15 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 38604830b88..8abed5c14cb 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/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 +1469,40 @@ Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
     }
   }
 
+  if (AllowReassociate &&
+      Op0->hasOneUse() && Op1->hasOneUse()) {
+    Value *A;
+    // sin(a) / cos(a) -> tan(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);
+      }
+    }
+
+    // cos(a) / sin(a) -> 1/tan(a)
+    if (match(Op0, m_Intrinsic<Intrinsic::cos>(m_Value(A))) &&
+        match(Op1, m_Intrinsic<Intrinsic::sin>(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());
+        Value *One = ConstantFP::get(Tan->getType(), 1.0);
+        Value *Div = B.CreateFDiv(One, Tan);
+        return replaceInstUsesWith(I, Div);
+      }
+    }
+  }
+
   Value *LHS;
   Value *RHS;
 
diff --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
index b60dfb4f354..d4cf03c326d 100644
--- a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
@@ -709,6 +709,19 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
   }
 }
 
+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) {
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 03a1d55ddc3..dcdff3e96b3 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -104,21 +104,6 @@ static bool callHasFloatingPointArgument(const CallInst *CI) {
   });
 }
 
-/// \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
 //===----------------------------------------------------------------------===//