[PATCH] D93219: [CodeGen] Removes unwanted optimisation for TargetConstantFP

[Simon via Phabricator via llvm-commits]

simveg created this revision.
simveg added reviewers: efriedma, t.p.northover, dsanders.
Herald added a subscriber: hiraditya.
simveg requested review of this revision.
Herald added a project: LLVM.

This 'FIXME' popped up in the development of an out-of-tree backend. 
Quick fix, but first llvm upstream patch, therefore I do not have commit rights, so if approved please commit?

- Test is not included as this came up in an out-of-tree backend (if required, please hint on how to test this).
- Did not break tests in the current test suite.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D93219

Files:
  llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp


Index: llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -430,7 +430,6 @@
 
   LLVM_DEBUG(dbgs() << "Optimizing float store operations\n");
   // Turn 'store float 1.0, Ptr' -> 'store int 0x12345678, Ptr'
-  // FIXME: We shouldn't do this for TargetConstantFP's.
   // FIXME: move this to the DAG Combiner!  Note that we can't regress due
   // to phase ordering between legalized code and the dag combiner.  This
   // probably means that we need to integrate dag combiner and legalizer
@@ -438,10 +437,16 @@
   // We generally can't do this one for long doubles.
   SDValue Chain = ST->getChain();
   SDValue Ptr = ST->getBasePtr();
+  SDValue Value = ST->getValue();
   MachineMemOperand::Flags MMOFlags = ST->getMemOperand()->getFlags();
   AAMDNodes AAInfo = ST->getAAInfo();
   SDLoc dl(ST);
-  if (ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(ST->getValue())) {
+
+  // Don't optimise TargetConstantFP
+  if (Value.getOpcode() == ISD::TargetConstantFP)
+    return SDValue(nullptr, 0);
+
+  if (ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(Value)) {
     if (CFP->getValueType(0) == MVT::f32 &&
         TLI.isTypeLegal(MVT::i32)) {
       SDValue Con = DAG.getConstant(CFP->getValueAPF().


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