From 80fb24a66f54bd305b9c32f8f257447a14a78629 Mon Sep 17 00:00:00 2001
From: Cameron McInally <cameron.mcinally@nyu.edu>
Date: Fri, 3 May 2019 21:19:12 +0000
Subject: [PATCH] Update PatternMatcher for FNeg

Match both FNeg(X) and FSub(+-0.0, X) in FNeg_match

Differential Revision: https://reviews.llvm.org/D61520

llvm-svn: 359936
---
 include/llvm/IR/PatternMatch.h | 30 +++++++++++++++++++-----------
 unittests/IR/PatternMatch.cpp  | 29 +++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 11 deletions(-)

diff --git a/include/llvm/IR/PatternMatch.h b/include/llvm/IR/PatternMatch.h
index 6c51d487737..d310f07d336 100644
--- a/include/llvm/IR/PatternMatch.h
+++ b/include/llvm/IR/PatternMatch.h
@@ -667,18 +667,26 @@ template <typename Op_t> struct FNeg_match {
   FNeg_match(const Op_t &Op) : X(Op) {}
   template <typename OpTy> bool match(OpTy *V) {
     auto *FPMO = dyn_cast<FPMathOperator>(V);
-    if (!FPMO || FPMO->getOpcode() != Instruction::FSub)
-      return false;
-    if (FPMO->hasNoSignedZeros()) {
-      // With 'nsz', any zero goes.
-      if (!cstfp_pred_ty<is_any_zero_fp>().match(FPMO->getOperand(0)))
-        return false;
-    } else {
-      // Without 'nsz', we need fsub -0.0, X exactly.
-      if (!cstfp_pred_ty<is_neg_zero_fp>().match(FPMO->getOperand(0)))
-        return false;
+    if (!FPMO) return false;
+
+    if (FPMO->getOpcode() == Instruction::FNeg)
+      return X.match(FPMO->getOperand(0));
+
+    if (FPMO->getOpcode() == Instruction::FSub) {
+      if (FPMO->hasNoSignedZeros()) {
+        // With 'nsz', any zero goes.
+        if (!cstfp_pred_ty<is_any_zero_fp>().match(FPMO->getOperand(0)))
+          return false;
+      } else {
+        // Without 'nsz', we need fsub -0.0, X exactly.
+        if (!cstfp_pred_ty<is_neg_zero_fp>().match(FPMO->getOperand(0)))
+          return false;
+      }
+
+      return X.match(FPMO->getOperand(1));
     }
-    return X.match(FPMO->getOperand(1));
+
+    return false;
   }
 };
 
diff --git a/unittests/IR/PatternMatch.cpp b/unittests/IR/PatternMatch.cpp
index e380fb90ad7..de47975e7c6 100644
--- a/unittests/IR/PatternMatch.cpp
+++ b/unittests/IR/PatternMatch.cpp
@@ -589,6 +589,35 @@ TEST_F(PatternMatchTest, VectorUndefFloat) {
   EXPECT_TRUE(match(VectorZeroUndef, m_AnyZeroFP()));
 }
 
+TEST_F(PatternMatchTest, FloatingPointFNeg) {
+  Type *FltTy = IRB.getFloatTy();
+  Value *One = ConstantFP::get(FltTy, 1.0);
+  Value *Z = ConstantFP::get(FltTy, 0.0);
+  Value *NZ = ConstantFP::get(FltTy, -0.0);
+  Value *V = IRB.CreateFNeg(One);
+  Value *V1 = IRB.CreateFSub(NZ, One);
+  Value *V2 = IRB.CreateFSub(Z, One);
+  Value *V3 = IRB.CreateFAdd(NZ, One);
+  Value *Match;
+
+  // Test FNeg(1.0)
+  EXPECT_TRUE(match(V, m_FNeg(m_Value(Match))));
+  EXPECT_EQ(One, Match);
+
+  // Test FSub(-0.0, 1.0)
+  EXPECT_TRUE(match(V1, m_FNeg(m_Value(Match))));
+  EXPECT_EQ(One, Match);
+
+  // Test FSub(0.0, 1.0)
+  EXPECT_FALSE(match(V2, m_FNeg(m_Value(Match))));
+  cast<Instruction>(V2)->setHasNoSignedZeros(true);
+  EXPECT_TRUE(match(V2, m_FNeg(m_Value(Match))));
+  EXPECT_EQ(One, Match);
+
+  // Test FAdd(-0.0, 1.0)
+  EXPECT_FALSE(match(V3, m_FNeg(m_Value(Match))));
+}
+
 template <typename T> struct MutableConstTest : PatternMatchTest { };
 
 typedef ::testing::Types<std::tuple<Value*, Instruction*>,