[PATCH] D131491: [LoongArch] Override TargetLowering::isOffsetFoldingLegal()

[Ray Wang via Phabricator via llvm-commits]

wangleiat created this revision.
wangleiat added reviewers: MaskRay, xen0n, SixWeining, xry111, gonglingqin.
Herald added subscribers: StephenFan, hiraditya.
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wangleiat requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

This patch disable GlobalAddress+Offset folding.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D131491

Files:
  llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp
  llvm/lib/Target/LoongArch/LoongArchISelLowering.h
  llvm/test/CodeGen/LoongArch/ir-instruction/load-store.ll


Index: llvm/test/CodeGen/LoongArch/ir-instruction/load-store.ll
===================================================================
--- llvm/test/CodeGen/LoongArch/ir-instruction/load-store.ll
+++ llvm/test/CodeGen/LoongArch/ir-instruction/load-store.ll
@@ -45,8 +45,8 @@
 ; LA32PIC-NEXT:     addi.w $a2, $a1, .Larr$local
 ; LA32-NEXT:        ld.w $a1, $a2, 0
 ; LA32-NEXT:        st.w $a0, $a2, 0
-; LA32NOPIC-NEXT:   ld.w $a3, $a2, 0
-; LA32NOPIC-NEXT:   st.w $a0, $a2, 0
+; LA32NOPIC-NEXT:   ld.w $a3, $a2, 36
+; LA32NOPIC-NEXT:   st.w $a0, $a2, 36
 ; LA32PIC-NEXT:     ld.w $a3, $a2, 36
 ; LA32PIC-NEXT:     st.w $a0, $a2, 36
 
@@ -56,8 +56,8 @@
 ; LA64PIC-NEXT:     addi.d $a2, $a1, .Larr$local
 ; LA64-NEXT:        ld.w $a1, $a2, 0
 ; LA64-NEXT:        st.w $a0, $a2, 0
-; LA64NOPIC-NEXT:   ld.w $a3, $a2, 0
-; LA64NOPIC-NEXT:   st.w $a0, $a2, 0
+; LA64NOPIC-NEXT:   ld.w $a3, $a2, 36
+; LA64NOPIC-NEXT:   st.w $a0, $a2, 36
 ; LA64PIC-NEXT:     ld.w $a3, $a2, 36
 ; LA64PIC-NEXT:     st.w $a0, $a2, 36
 
Index: llvm/lib/Target/LoongArch/LoongArchISelLowering.h
===================================================================
--- llvm/lib/Target/LoongArch/LoongArchISelLowering.h
+++ llvm/lib/Target/LoongArch/LoongArchISelLowering.h
@@ -62,6 +62,8 @@
 
   const LoongArchSubtarget &getSubtarget() const { return Subtarget; }
 
+  bool isOffsetFoldingLegal(const GlobalAddressSDNode *GA) const override;
+
   // Provide custom lowering hooks for some operations.
   SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const override;
   void ReplaceNodeResults(SDNode *N, SmallVectorImpl<SDValue> &Results,
Index: llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp
===================================================================
--- llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp
+++ llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp
@@ -122,6 +122,15 @@
   setTargetDAGCombine(ISD::SRL);
 }
 
+bool LoongArchTargetLowering::isOffsetFoldingLegal(
+    const GlobalAddressSDNode *GA) const {
+  // In order to maximise the opportunity for common subexpression elimination,
+  // keep a separate ADD node for the global address offset instead of folding
+  // it in the global address node. Later peephole optimisations may choose to
+  // fold it back in when profitable.
+  return false;
+}
+
 SDValue LoongArchTargetLowering::LowerOperation(SDValue Op,
                                                 SelectionDAG &DAG) const {
   switch (Op.getOpcode()) {


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