[RISCV] Add getSameRatioLMUL

[wangpc-pp]

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

[llvmbot]

@llvm/pr-subscribers-backend-risc-v

Author: Wang Pengcheng (wangpc-pp)

Changes

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

---

Full diff: https://github.com/llvm/llvm-project/pull/69570.diff

4 Files Affected:

• (modified) llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.cpp (+9)
• (modified) llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.h (+2)
• (modified) llvm/unittests/Target/RISCV/CMakeLists.txt (+1)
• (added) llvm/unittests/Target/RISCV/RISCVBaseInfoTest.cpp (+30)

diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.cpp
index d71efc11e6a9fcf..4bfd44592d6d90e 100644
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.cpp
+++ b/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, ) {
+  int Ratio = RISCVVType::getSEWLMULRatio(SEW, VLMUL);
+  int 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
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.h b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.h
index 20ff26a39dc3b30..e7181eadd497386 100644
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.h
+++ b/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 {
diff --git a/llvm/unittests/Target/RISCV/CMakeLists.txt b/llvm/unittests/Target/RISCV/CMakeLists.txt
index 2c757b82e5dce85..9d0bf7244c02210 100644
--- a/llvm/unittests/Target/RISCV/CMakeLists.txt
+++ b/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")
diff --git a/llvm/unittests/Target/RISCV/RISCVBaseInfoTest.cpp b/llvm/unittests/Target/RISCV/RISCVBaseInfoTest.cpp
new file mode 100644
index 000000000000000..3cc100c7b7c22c1
--- /dev/null
+++ b/llvm/unittests/Target/RISCV/RISCVBaseInfoTest.cpp
@@ -0,0 +1,30 @@
+//===- 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_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));
+  // Bigger fractional LMUL.
+  EXPECT_EQ(RISCVII::LMUL_F2,
+            RISCVVType::getSameRatioLMUL(8, RISCVII::LMUL_F4, 16));
+}
+} // namespace
\ No newline at end of file

[michaelmaitland]

LGTM.

[topperc]

LGTM