[llvm] [RISCV][llvm-mca] Vector Unit Stride Loads and stores use EEW and EMU… (PR #69409)

[Wang Pengcheng via llvm-commits]

================
@@ -185,6 +187,59 @@ RISCVInstrumentManager::createInstruments(const MCInst &Inst) {
   return SmallVector<UniqueInstrument>();
 }
 
+/// Return EMUL = (EEW / SEW) * LMUL
+inline static std::pair<unsigned, bool>
+getEMULEqualsEEWDivSEWTimesLMUL(unsigned EEW, unsigned SEW,
+                                RISCVII::VLMUL VLMUL) {
+  // Calculate (EEW/SEW)*LMUL preserving fractions less than 1. Use GCD
+  // to put fraction in simplest form.
+  auto [LMUL, Fractional] = RISCVVType::decodeVLMUL(VLMUL);
----------------
wangpc-pp wrote:

Can this function be simpler? For example, use `getSEWLMULRatio` (please verify the functionality):
```cpp
int Ratio = RISCVVType::getSEWLMULRatio(SEW, VLMUL);
int LMulFixedPoint = (EEW * 8) / Ratio;
bool Fractional = LMulFixedPoint < 8;
unsigned LMul = Fractional ? 8 / LMulFixedPoint : LMulFixedPoint / 8;
```

https://github.com/llvm/llvm-project/pull/69409