[PATCH] D143646: [RISCV] Return false from shouldFormOverflowOp

[Liao Chunyu via Phabricator via llvm-commits]

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This is related to the discussion in D142071 <https://reviews.llvm.org/D142071>. It can solve the regression in D142071 <https://reviews.llvm.org/D142071>.

I tested llvm/tests/Transforms/CodeGenPrepare/X86/overflow-intrinsics.ll, no new regression.

Usually MathUsed is Add->hasNUsesOrMore(2), for optbranch_64, the add just has two uses. 
MathUsed is true. If we could check these use must come from the same BB, perhaps MathUsed could be false.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D143646

Files:
  llvm/lib/Target/RISCV/RISCVISelLowering.h


Index: llvm/lib/Target/RISCV/RISCVISelLowering.h
===================================================================
--- llvm/lib/Target/RISCV/RISCVISelLowering.h
+++ llvm/lib/Target/RISCV/RISCVISelLowering.h
@@ -477,6 +477,11 @@
   EVT getSetCCResultType(const DataLayout &DL, LLVMContext &Context,
                          EVT VT) const override;
 
+  bool shouldFormOverflowOp(unsigned Opcode, EVT VT,
+                            bool MathUsed) const override {
+    return TargetLowering::shouldFormOverflowOp(Opcode, VT, false);
+  }
+
   bool convertSetCCLogicToBitwiseLogic(EVT VT) const override {
     return VT.isScalarInteger();
   }


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