From e818f770bb4f6617612e5b61cc067aa7da9e1395 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Fri, 2 May 2008 18:43:35 +0000
Subject: [PATCH] strength reduce exp2 into ldexp, rdar://5852514

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50586 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/SimplifyLibCalls.cpp | 53 +++++++++++++++++++++-
 test/Transforms/SimplifyLibCalls/exp2.ll   | 38 ++++++++++++++++
 2 files changed, 90 insertions(+), 1 deletion(-)
 create mode 100644 test/Transforms/SimplifyLibCalls/exp2.ll

diff --git a/lib/Transforms/Scalar/SimplifyLibCalls.cpp b/lib/Transforms/Scalar/SimplifyLibCalls.cpp
index e9c089dbd07..d43a181d732 100644
--- a/lib/Transforms/Scalar/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Scalar/SimplifyLibCalls.cpp
@@ -837,6 +837,53 @@ struct VISIBILITY_HIDDEN PowOpt : public LibCallOptimization {
   }
 };
 
+//===---------------------------------------===//
+// 'exp2' Optimizations
+
+struct VISIBILITY_HIDDEN Exp2Opt : public LibCallOptimization {
+  virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder &B) {
+    const FunctionType *FT = Callee->getFunctionType();
+    // Just make sure this has 1 argument of FP type, which matches the
+    // result type.
+    if (FT->getNumParams() != 1 || FT->getReturnType() != FT->getParamType(0) ||
+        !FT->getParamType(0)->isFloatingPoint())
+      return 0;
+    
+    Value *Op = CI->getOperand(1);
+    // Turn exp2(sitofp(x)) -> ldexp(1.0, sext(x))  if sizeof(x) <= 32
+    // Turn exp2(uitofp(x)) -> ldexp(1.0, zext(x))  if sizeof(x) < 32
+    Value *LdExpArg = 0;
+    if (SIToFPInst *OpC = dyn_cast<SIToFPInst>(Op)) {
+      if (OpC->getOperand(0)->getType()->getPrimitiveSizeInBits() <= 32)
+        LdExpArg = B.CreateSExt(OpC->getOperand(0), Type::Int32Ty, "tmp");
+    } else if (UIToFPInst *OpC = dyn_cast<UIToFPInst>(Op)) {
+      if (OpC->getOperand(0)->getType()->getPrimitiveSizeInBits() < 32)
+        LdExpArg = B.CreateZExt(OpC->getOperand(0), Type::Int32Ty, "tmp");
+    }
+    
+    if (LdExpArg) {
+      const char *Name;
+      if (Op->getType() == Type::FloatTy)
+        Name = "ldexpf";
+      else if (Op->getType() == Type::DoubleTy)
+        Name = "ldexp";
+      else
+        Name = "ldexpl";
+
+      Constant *One = ConstantFP::get(APFloat(1.0f));
+      if (Op->getType() != Type::FloatTy)
+        One = ConstantExpr::getFPExtend(One, Op->getType());
+
+      Module *M = Caller->getParent();
+      Value *Callee = M->getOrInsertFunction(Name, Op->getType(),
+                                             Op->getType(), Type::Int32Ty,NULL);
+      return B.CreateCall2(Callee, One, LdExpArg);
+    }
+    return 0;
+  }
+};
+    
+
 //===---------------------------------------===//
 // Double -> Float Shrinking Optimizations for Unary Functions like 'floor'
 
@@ -1205,7 +1252,7 @@ namespace {
     StrCatOpt StrCat; StrChrOpt StrChr; StrCmpOpt StrCmp; StrNCmpOpt StrNCmp;
     StrCpyOpt StrCpy; StrLenOpt StrLen; MemCmpOpt MemCmp; MemCpyOpt  MemCpy;
     // Math Library Optimizations
-    PowOpt Pow; UnaryDoubleFPOpt UnaryDoubleFP;
+    PowOpt Pow; Exp2Opt Exp2; UnaryDoubleFPOpt UnaryDoubleFP;
     // Integer Optimizations
     FFSOpt FFS; IsDigitOpt IsDigit; IsAsciiOpt IsAscii; ToAsciiOpt ToAscii;
     // Formatting and IO Optimizations
@@ -1253,6 +1300,10 @@ void SimplifyLibCalls::InitOptimizations() {
   Optimizations["powf"] = &Pow;
   Optimizations["pow"] = &Pow;
   Optimizations["powl"] = &Pow;
+  Optimizations["exp2l"] = &Exp2;
+  Optimizations["exp2"] = &Exp2;
+  Optimizations["exp2f"] = &Exp2;
+  
 #ifdef HAVE_FLOORF
   Optimizations["floor"] = &UnaryDoubleFP;
 #endif
diff --git a/test/Transforms/SimplifyLibCalls/exp2.ll b/test/Transforms/SimplifyLibCalls/exp2.ll
new file mode 100644
index 00000000000..dea3df4b51b
--- /dev/null
+++ b/test/Transforms/SimplifyLibCalls/exp2.ll
@@ -0,0 +1,38 @@
+; RUN: llvm-as < %s | opt -simplify-libcalls | llvm-dis | grep {call.*ldexp} | count 4
+; rdar://5852514
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+target triple = "i386-apple-darwin8"
+
+define double @t1(i32 %x) nounwind  {
+entry:
+	%tmp12 = sitofp i32 %x to double		; <double> [#uses=1]
+	%exp2 = tail call double @exp2( double %tmp12 )		; <double> [#uses=1]
+	ret double %exp2
+}
+
+define float @t4(i8 zeroext  %x) nounwind  {
+entry:
+	%tmp12 = uitofp i8 %x to float		; <float> [#uses=1]
+	%tmp3 = tail call float @exp2f( float %tmp12 ) nounwind readonly 		; <float> [#uses=1]
+	ret float %tmp3
+}
+
+declare float @exp2f(float) nounwind readonly 
+
+define double @t3(i16 zeroext  %x) nounwind  {
+entry:
+	%tmp12 = uitofp i16 %x to double		; <double> [#uses=1]
+	%exp2 = tail call double @exp2( double %tmp12 )		; <double> [#uses=1]
+	ret double %exp2
+}
+
+define double @t2(i16 signext  %x) nounwind  {
+entry:
+	%tmp12 = sitofp i16 %x to double		; <double> [#uses=1]
+	%exp2 = tail call double @exp2( double %tmp12 )		; <double> [#uses=1]
+	ret double %exp2
+}
+
+declare double @exp2(double)
+