[RISCV] Add getSameRatioLMUL (#69570)

To calculate the LMUL with the same SEW/LMUL ratio when providing
EEW.

Author: wangpc-pp

llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.cpp

@@ -206,6 +206,15 @@ unsigned RISCVVType::getSEWLMULRatio(unsigned SEW, RISCVII::VLMUL VLMul) {
   return (SEW * 8) / LMul;
 }
 
+RISCVII::VLMUL RISCVVType::getSameRatioLMUL(unsigned SEW, RISCVII::VLMUL VLMUL,
+                                            unsigned EEW) {
+  unsigned Ratio = RISCVVType::getSEWLMULRatio(SEW, VLMUL);
+  unsigned EMULFixedPoint = (EEW * 8) / Ratio;
+  bool Fractional = EMULFixedPoint < 8;
+  unsigned EMUL = Fractional ? 8 / EMULFixedPoint : EMULFixedPoint / 8;
+  return RISCVVType::encodeLMUL(EMUL, Fractional);
+}
+
 // Include the auto-generated portion of the compress emitter.
 #define GEN_UNCOMPRESS_INSTR
 #define GEN_COMPRESS_INSTR

llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.h

@@ -535,6 +535,8 @@ void printVType(unsigned VType, raw_ostream &OS);
 
 unsigned getSEWLMULRatio(unsigned SEW, RISCVII::VLMUL VLMul);
 
+RISCVII::VLMUL getSameRatioLMUL(unsigned SEW, RISCVII::VLMUL VLMUL,
+                                unsigned EEW);
 } // namespace RISCVVType
 
 namespace RISCVRVC {

llvm/unittests/Target/RISCV/CMakeLists.txt

@@ -13,6 +13,7 @@ set(LLVM_LINK_COMPONENTS
 
 add_llvm_target_unittest(RISCVTests
   MCInstrAnalysisTest.cpp
+  RISCVBaseInfoTest.cpp
   )
 
 set_property(TARGET RISCVTests PROPERTY FOLDER "Tests/UnitTests/TargetTests")

llvm/unittests/Target/RISCV/RISCVBaseInfoTest.cpp

@@ -0,0 +1,34 @@
+//===- RISCVBaseInfoTest.cpp - RISCVBaseInfo unit tests ----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "MCTargetDesc/RISCVBaseInfo.h"
+
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+TEST(RISCVBaseInfo, CheckSameRatioLMUL) {
+  // Smaller LMUL.
+  EXPECT_EQ(RISCVII::LMUL_1,
+            RISCVVType::getSameRatioLMUL(16, RISCVII::LMUL_2, 8));
+  EXPECT_EQ(RISCVII::LMUL_F2,
+            RISCVVType::getSameRatioLMUL(16, RISCVII::LMUL_1, 8));
+  // Smaller fractional LMUL.
+  EXPECT_EQ(RISCVII::LMUL_F8,
+            RISCVVType::getSameRatioLMUL(16, RISCVII::LMUL_F4, 8));
+  // Bigger LMUL.
+  EXPECT_EQ(RISCVII::LMUL_2,
+            RISCVVType::getSameRatioLMUL(8, RISCVII::LMUL_1, 16));
+  EXPECT_EQ(RISCVII::LMUL_1,
+            RISCVVType::getSameRatioLMUL(8, RISCVII::LMUL_F2, 16));
+  // Bigger fractional LMUL.
+  EXPECT_EQ(RISCVII::LMUL_F2,
+            RISCVVType::getSameRatioLMUL(8, RISCVII::LMUL_F4, 16));
+}
+} // namespace