[llvm] a9e9397 - [CodeGen] Removes unwanted optimisation for TargetConstantFP

[Craig Topper via llvm-commits]

Author: Craig Topper
Date: 2021-01-15T11:52:53-08:00
New Revision: a9e939760c6f21476109559cc3e21779bddddaff

URL: https://github.com/llvm/llvm-project/commit/a9e939760c6f21476109559cc3e21779bddddaff
DIFF: https://github.com/llvm/llvm-project/commit/a9e939760c6f21476109559cc3e21779bddddaff.diff

LOG: [CodeGen] Removes unwanted optimisation for TargetConstantFP

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).

Patch by simveg (Simon)

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D93219

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 523895200f6a..2437b07e7d0e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -431,7 +431,6 @@ SDValue SelectionDAGLegalize::OptimizeFloatStore(StoreSDNode* ST) {
 
   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
@@ -439,10 +438,16 @@ SDValue SelectionDAGLegalize::OptimizeFloatStore(StoreSDNode* ST) {
   // 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();
+
+  if (ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(Value)) {
     if (CFP->getValueType(0) == MVT::f32 &&
         TLI.isTypeLegal(MVT::i32)) {
       SDValue Con = DAG.getConstant(CFP->getValueAPF().
@@ -482,7 +487,7 @@ SDValue SelectionDAGLegalize::OptimizeFloatStore(StoreSDNode* ST) {
       }
     }
   }
-  return SDValue(nullptr, 0);
+  return SDValue();
 }
 
 void SelectionDAGLegalize::LegalizeStoreOps(SDNode *Node) {