[PATCH] D45598: [DAGCombiner, PowerPC] allow X - (fpext(-Y) --> X + fpext(Y) with multiple uses

[Sanjay Patel via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL330098: [DAGCombiner, PowerPC] allow X - (fpext(-Y) --> X + fpext(Y) with multiple uses (authored by spatel, committed by ).

Changed prior to commit:
  https://reviews.llvm.org/D45598?vs=142278&id=142576#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D45598

Files:
  llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/trunk/test/CodeGen/PowerPC/fsub-fneg.ll


Index: llvm/trunk/test/CodeGen/PowerPC/fsub-fneg.ll
===================================================================
--- llvm/trunk/test/CodeGen/PowerPC/fsub-fneg.ll
+++ llvm/trunk/test/CodeGen/PowerPC/fsub-fneg.ll
@@ -1,16 +1,16 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc -verify-machineinstrs -mtriple=powerpc64le < %s | FileCheck %s
 
-; FIXME: When fpext is free, we should look through it for optimizations
+; When fpext is free, we should look through it for optimizations
 ; even if it has multiple uses and produce an 'fadd' here.
 ; Y - (fpext(-X)) --> Y + fpext(X)
 
 define double @neg_ext_op1_extra_use(float %x, double %y) nounwind {
 ; CHECK-LABEL: neg_ext_op1_extra_use:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    fneg 0, 1
-; CHECK-NEXT:    xssubdp 1, 2, 0
-; CHECK-NEXT:    xsdivdp 1, 0, 1
+; CHECK-NEXT:    xsadddp 0, 2, 1
+; CHECK-NEXT:    fneg 13, 1
+; CHECK-NEXT:    xsdivdp 1, 13, 0
 ; CHECK-NEXT:    blr
   %t1 = fsub float -0.0, %x
   %t2 = fpext float %t1 to double
Index: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -667,13 +667,16 @@
   // fneg is removable even if it has multiple uses.
   if (Op.getOpcode() == ISD::FNEG) return 2;
 
-  // Don't allow anything with multiple uses.
-  if (!Op.hasOneUse()) return 0;
+  // Don't allow anything with multiple uses unless we know it is free.
+  EVT VT = Op.getValueType();
+  if (!Op.hasOneUse())
+    if (!(Op.getOpcode() == ISD::FP_EXTEND &&
+          TLI.isFPExtFree(VT, Op.getOperand(0).getValueType())))
+      return 0;
 
   // Don't recurse exponentially.
   if (Depth > 6) return 0;
 
-  EVT VT = Op.getValueType();
   switch (Op.getOpcode()) {
   default: return false;
   case ISD::ConstantFP: {
@@ -736,9 +739,6 @@
   // fneg is removable even if it has multiple uses.
   if (Op.getOpcode() == ISD::FNEG) return Op.getOperand(0);
 
-  // Don't allow anything with multiple uses.
-  assert(Op.hasOneUse() && "Unknown reuse!");
-
   assert(Depth <= 6 && "GetNegatedExpression doesn't match isNegatibleForFree");
 
   const SDNodeFlags Flags = Op.getNode()->getFlags();


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D45598.142576.patch
Type: text/x-patch
Size: 2299 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20180415/48016c19/attachment.bin>