[llvm] [RISCV] Implement foward inserting save/restore FRM instructions. (PR #77744)

[Yeting Kuo via llvm-commits]

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@@ -99,8 +181,12 @@ bool RISCVInsertReadWriteCSR::runOnMachineFunction(MachineFunction &MF) {
 
   bool Changed = false;
 
-  for (MachineBasicBlock &MBB : MF)
-    Changed |= emitWriteRoundingMode(MBB);
+  for (MachineBasicBlock &MBB : MF) {
+    if (DisableFRMInsertOpt)
+      Changed |= emitWriteRoundingMode(MBB);
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yetingk wrote:

BTW, I had added unoptimized test cases in llvm/test/CodeGen/RISCV/rvv/frm-insert.ll

https://github.com/llvm/llvm-project/pull/77744