From 8ba631d9c8b5f1b4e4e314c1f4b366c58a71b4a5 Mon Sep 17 00:00:00 2001
From: Sanjay Patel <spatel@rotateright.com>
Date: Thu, 16 Aug 2018 22:46:20 +0000
Subject: [PATCH] [InstCombine] add reflection fold for tan(-x)

This is a follow-up suggested with rL339604.
For tan(), we don't have a corresponding LLVM
intrinsic -- unlike sin/cos -- so this is the
only way/place that we can do this fold currently.

llvm-svn: 339958
---
 llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp |  7 +++++--
 llvm/test/Transforms/InstCombine/cos-1.ll      | 12 ++++++------
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index a0f1f8185ece..865720b416b9 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -1130,16 +1130,19 @@ static Value *optimizeTrigReflections(CallInst *Call, LibFunc Func,
   IRBuilder<>::FastMathFlagGuard Guard(B);
   B.setFastMathFlags(Call->getFastMathFlags());
   
-  // TODO: Add tan() and other calls.
   // TODO: Can this be shared to also handle LLVM intrinsics?
   Value *X;
   switch (Func) {
   case LibFunc_sin:
   case LibFunc_sinf:
   case LibFunc_sinl:
+  case LibFunc_tan:
+  case LibFunc_tanf:
+  case LibFunc_tanl:
     // sin(-X) --> -sin(X)
+    // tan(-X) --> -tan(X)
     if (match(Call->getArgOperand(0), m_OneUse(m_FNeg(m_Value(X)))))
-      return B.CreateFNeg(B.CreateCall(Call->getCalledFunction(), X, "sin"));
+      return B.CreateFNeg(B.CreateCall(Call->getCalledFunction(), X));
     break;
   case LibFunc_cos:
   case LibFunc_cosf:
diff --git a/llvm/test/Transforms/InstCombine/cos-1.ll b/llvm/test/Transforms/InstCombine/cos-1.ll
index 9900f191bfbb..50db2a98e83b 100644
--- a/llvm/test/Transforms/InstCombine/cos-1.ll
+++ b/llvm/test/Transforms/InstCombine/cos-1.ll
@@ -117,9 +117,9 @@ define double @neg_sin_negated_arg(double %x) {
 
 define double @tan_negated_arg(double %x) {
 ; ANY-LABEL: @tan_negated_arg(
-; ANY-NEXT:    [[NEG:%.*]] = fsub double -0.000000e+00, [[X:%.*]]
-; ANY-NEXT:    [[R:%.*]] = call double @tan(double [[NEG]])
-; ANY-NEXT:    ret double [[R]]
+; ANY-NEXT:    [[TMP1:%.*]] = call double @tan(double [[X:%.*]])
+; ANY-NEXT:    [[TMP2:%.*]] = fsub double -0.000000e+00, [[TMP1]]
+; ANY-NEXT:    ret double [[TMP2]]
 ;
   %neg = fsub double -0.0, %x
   %r = call double @tan(double %neg)
@@ -130,9 +130,9 @@ define double @tan_negated_arg(double %x) {
 
 define fp128 @tanl_negated_arg(fp128 %x) {
 ; ANY-LABEL: @tanl_negated_arg(
-; ANY-NEXT:    [[NEG:%.*]] = fsub fp128 0xL00000000000000008000000000000000, [[X:%.*]]
-; ANY-NEXT:    [[R:%.*]] = call fp128 @tanl(fp128 [[NEG]])
-; ANY-NEXT:    ret fp128 [[R]]
+; ANY-NEXT:    [[TMP1:%.*]] = call fp128 @tanl(fp128 [[X:%.*]])
+; ANY-NEXT:    [[TMP2:%.*]] = fsub fp128 0xL00000000000000008000000000000000, [[TMP1]]
+; ANY-NEXT:    ret fp128 [[TMP2]]
 ;
   %neg = fsub fp128 0xL00000000000000008000000000000000, %x
   %r = call fp128 @tanl(fp128 %neg)