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

[Wang Pengcheng via llvm-commits]

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@@ -185,6 +187,109 @@ 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);
+  unsigned Num = EEW, Denom = SEW;
+  int GCD =
+      Fractional ? std::gcd(Num, Denom * LMUL) : std::gcd(Num * LMUL, Denom);
+  Num = Fractional ? Num / GCD : Num * LMUL / GCD;
+  Denom = Fractional ? Denom * LMUL / GCD : Denom / GCD;
+  return std::make_pair(Num > Denom ? Num : Denom, Denom > Num);
+}
+
+static std::pair<uint8_t, uint8_t>
+getEEWAndEMULForUnitStrideLoadStore(unsigned Opcode, uint8_t LMUL,
+                                    uint8_t SEW) {
+  uint8_t EEW;
+  switch (Opcode) {
+  case RISCV::VLM_V:
+  case RISCV::VSM_V:
+  case RISCV::VLE8_V:
+  case RISCV::VSE8_V:
+    EEW = 8;
+    break;
+  case RISCV::VLE16_V:
+  case RISCV::VSE16_V:
+    EEW = 16;
+    break;
+  case RISCV::VLE32_V:
+  case RISCV::VSE32_V:
+    EEW = 32;
+    break;
+  case RISCV::VLE64_V:
+  case RISCV::VSE64_V:
+    EEW = 64;
+    break;
+  default:
+    llvm_unreachable("Opcode is not a vector unit stride load nor store");
+  }
+
+  RISCVII::VLMUL VLMUL;
+  switch (LMUL) {
+  case 0b000:
+    VLMUL = RISCVII::LMUL_1;
+    break;
+  case 0b001:
+    VLMUL = RISCVII::LMUL_2;
+    break;
+  case 0b010:
+    VLMUL = RISCVII::LMUL_4;
+    break;
+  case 0b011:
+    VLMUL = RISCVII::LMUL_8;
+    break;
+  case 0b111:
+    VLMUL = RISCVII::LMUL_F2;
+    break;
+  case 0b110:
+    VLMUL = RISCVII::LMUL_F4;
+    break;
+  case 0b101:
+    VLMUL = RISCVII::LMUL_F8;
+    break;
+  case RISCVII::LMUL_RESERVED:
+    llvm_unreachable("LMUL cannot be LMUL_RESERVED");
+  }
+
+  auto [EMULPart, Fractional] =
+      getEMULEqualsEEWDivSEWTimesLMUL(EEW, SEW, VLMUL);
+  assert(RISCVVType::isValidLMUL(EMULPart, Fractional) &&
+         "Unexpected EEW from instruction used with LMUL and SEW");
+
+  uint8_t EMUL;
+  switch (RISCVVType::encodeLMUL(EMULPart, Fractional)) {
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wangpc-pp wrote:

This conversion can also be `static_cast` too.

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