From d8a029c81ba59fa53847ab7784ff5fb81ea0d1fe Mon Sep 17 00:00:00 2001
From: Owen Anderson <resistor@mac.com>
Date: Thu, 30 Apr 2015 04:06:32 +0000
Subject: [PATCH] Semantically revert r236031, which is not a good idea for
 in-order targets.

At the least it should be guarded by some kind of target hook.
It also introduced catastrophic compile time and code quality
regressions on some out of tree targets (test case still being
reduced/sanitized).

Sanjay agreed with reverting this patch until these issues can be
resolved.

llvm-svn: 236199
---
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 31 --------------------
 llvm/test/CodeGen/X86/fp-fast.ll              | 42 ---------------------------
 2 files changed, 73 deletions(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 2a9f8e1..a5f558f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7647,33 +7647,6 @@ SDValue DAGCombiner::visitFSUBForFMACombine(SDNode *N) {
   return SDValue();
 }
 
-static SDValue ReassociateBinops(SDNode *N, SelectionDAG &DAG) {
-  assert(N->getNumOperands() == 2 && "Invalid node for binop reassociation");
-  SDValue N0 = N->getOperand(0);
-  SDValue N1 = N->getOperand(1);
-  EVT VT = N->getValueType(0);
-  SDLoc DL(N);
-  unsigned Opcode = N->getOpcode();
-
-  // Canonicalize chains of this operation to LHS to allow the following fold.
-  if (N0.getOpcode() != Opcode && N1.getOpcode() == Opcode)
-    return DAG.getNode(Opcode, DL, VT, N1, N0);
-  
-  // Convert a chain of 3 dependent operations into 2 independent operations
-  // and 1 dependent operation:
-  //  (op N0: (op N00: (op z, w), N01: y), N1: x) ->
-  //  (op N00: (op z, w), (op N1: x, N01: y))
-  if (N0.getOpcode() == Opcode && N0.hasOneUse() && N1.getOpcode() != Opcode) {
-    SDValue N00 = N0.getOperand(0);
-    if (N00.getOpcode() == Opcode) {
-      SDValue N01 = N0.getOperand(1);
-      SDValue NewOp = DAG.getNode(Opcode, DL, VT, N1, N01);
-      return DAG.getNode(Opcode, DL, VT, N00, NewOp);
-    }
-  }
-  return SDValue();
-}
-
 SDValue DAGCombiner::visitFADD(SDNode *N) {
   SDValue N0 = N->getOperand(0);
   SDValue N1 = N->getOperand(1);
@@ -7808,10 +7781,6 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
                            N0.getOperand(0), DAG.getConstantFP(4.0, DL, VT));
       }
     }
-    
-    if (SDValue Reassociated = ReassociateBinops(N, DAG))
-      return Reassociated;
-
   } // enable-unsafe-fp-math
 
   // FADD -> FMA combines:
diff --git a/llvm/test/CodeGen/X86/fp-fast.ll b/llvm/test/CodeGen/X86/fp-fast.ll
index eb2ebd9..27af573 100644
--- a/llvm/test/CodeGen/X86/fp-fast.ll
+++ b/llvm/test/CodeGen/X86/fp-fast.ll
@@ -114,45 +114,3 @@ define float @test11(float %a) {
   ret float %t2
 }
 
-; Verify that the first two adds are independent; the destination registers
-; are used as source registers for the third add.
-
-define float @reassociate_adds1(float %a, float %b, float %c, float %d) {
-; CHECK-LABEL: reassociate_adds1:
-; CHECK:       # BB#0:
-; CHECK-NEXT:    vaddss %xmm1, %xmm0, %xmm0
-; CHECK-NEXT:    vaddss %xmm2, %xmm3, %xmm1
-; CHECK-NEXT:    vaddss %xmm1, %xmm0, %xmm0
-; CHECK-NEXT:    retq
-  %add0 = fadd float %a, %b
-  %add1 = fadd float %add0, %c
-  %add2 = fadd float %add1, %d
-  ret float %add2
-}
-
-define float @reassociate_adds2(float %a, float %b, float %c, float %d) {
-; CHECK-LABEL: reassociate_adds2:
-; CHECK:       # BB#0:
-; CHECK-NEXT:    vaddss %xmm1, %xmm0, %xmm0
-; CHECK-NEXT:    vaddss %xmm2, %xmm3, %xmm1
-; CHECK-NEXT:    vaddss %xmm1, %xmm0, %xmm0
-; CHECK-NEXT:    retq
-  %add0 = fadd float %a, %b
-  %add1 = fadd float %c, %add0
-  %add2 = fadd float %add1, %d
-  ret float %add2
-}
-
-define float @reassociate_adds3(float %a, float %b, float %c, float %d) {
-; CHECK-LABEL: reassociate_adds3:
-; CHECK:       # BB#0:
-; CHECK-NEXT:    vaddss %xmm1, %xmm0, %xmm0
-; CHECK-NEXT:    vaddss %xmm2, %xmm3, %xmm1
-; CHECK-NEXT:    vaddss %xmm1, %xmm0, %xmm0
-; CHECK-NEXT:    retq
-  %add0 = fadd float %a, %b
-  %add1 = fadd float %add0, %c
-  %add2 = fadd float %d, %add1
-  ret float %add2
-}
-
-- 
2.7.4