[llvm] 9ae04a7 - [RISCV] Don't set nsw/nuw/exact flag after MachineCombiner reassociation.

[Craig Topper via llvm-commits]

Author: Craig Topper
Date: 2023-11-19T11:08:28-08:00
New Revision: 9ae04a77d12667d1fe8a2392240a85bde9e490fc

URL: https://github.com/llvm/llvm-project/commit/9ae04a77d12667d1fe8a2392240a85bde9e490fc
DIFF: https://github.com/llvm/llvm-project/commit/9ae04a77d12667d1fe8a2392240a85bde9e490fc.diff

LOG: [RISCV] Don't set nsw/nuw/exact flag after MachineCombiner reassociation.

This matches what PowerPC and X86 do.

Added: 
    

Modified: 
    llvm/lib/Target/RISCV/RISCVInstrInfo.cpp

Removed: 
    


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diff  --git a/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp b/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
index 67658aa1dfb6b28..a8ec93c3d5069f0 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
@@ -1614,9 +1614,18 @@ void RISCVInstrInfo::setSpecialOperandAttr(MachineInstr &OldMI1,
                                            MachineInstr &OldMI2,
                                            MachineInstr &NewMI1,
                                            MachineInstr &NewMI2) const {
+  // Propagate FP flags from the original instructions.
+  // But clear poison-generating flags because those may not be valid now.
   uint32_t IntersectedFlags = OldMI1.getFlags() & OldMI2.getFlags();
   NewMI1.setFlags(IntersectedFlags);
+  NewMI1.clearFlag(MachineInstr::MIFlag::NoSWrap);
+  NewMI1.clearFlag(MachineInstr::MIFlag::NoUWrap);
+  NewMI1.clearFlag(MachineInstr::MIFlag::IsExact);
+
   NewMI2.setFlags(IntersectedFlags);
+  NewMI2.clearFlag(MachineInstr::MIFlag::NoSWrap);
+  NewMI2.clearFlag(MachineInstr::MIFlag::NoUWrap);
+  NewMI2.clearFlag(MachineInstr::MIFlag::IsExact);
 }
 
 void RISCVInstrInfo::finalizeInsInstrs(