From fa273ae7c07c24906fe334abed4632054e4c5fc4 Mon Sep 17 00:00:00 2001
From: jacquesguan <jacquesguan@me.com>
Date: Sat, 17 Jul 2021 12:45:34 +0800
Subject: [PATCH] [RISCV] Make VLEN no greater than 65536

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D106134
---
 lib/Target/RISCV/RISCVRegisterInfo.td |  3 +--
 lib/Target/RISCV/RISCVSubtarget.cpp   | 18 ++++++++++--------
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/lib/Target/RISCV/RISCVRegisterInfo.td b/lib/Target/RISCV/RISCVRegisterInfo.td
index 320a7687a6c..fde75206889 100644
--- a/lib/Target/RISCV/RISCVRegisterInfo.td
+++ b/lib/Target/RISCV/RISCVRegisterInfo.td
@@ -285,8 +285,7 @@ def FPR64C : RegisterClass<"RISCV", [f64], 64, (add
 
 // Vector type mapping to LLVM types.
 //
-// Though the V extension allows that VLEN be as small as 8,
-// this approach assumes that VLEN>=64.
+// The V vector extension requires that VLEN >= 128 and <= 65536.
 // Additionally, the only supported ELEN values are 32 and 64,
 // thus `vscale` can be defined as VLEN/64,
 // allowing the same types with either ELEN value.
diff --git a/lib/Target/RISCV/RISCVSubtarget.cpp b/lib/Target/RISCV/RISCVSubtarget.cpp
index c8764b5b4ff..b19fdcb0082 100644
--- a/lib/Target/RISCV/RISCVSubtarget.cpp
+++ b/lib/Target/RISCV/RISCVSubtarget.cpp
@@ -109,30 +109,32 @@ unsigned RISCVSubtarget::getMaxRVVVectorSizeInBits() const {
   assert(hasStdExtV() && "Tried to get vector length without V support!");
   if (RVVVectorBitsMax == 0)
     return 0;
-  assert(RVVVectorBitsMax >= 128 && isPowerOf2_32(RVVVectorBitsMax) &&
-         "V extension requires vector length to be at least 128 and a power of "
-         "2!");
+  assert(RVVVectorBitsMax >= 128 && RVVVectorBitsMax <= 65536 &&
+         isPowerOf2_32(RVVVectorBitsMax) &&
+         "V extension requires vector length to be in the range of 128 to "
+         "65536 and a power of 2!");
   assert(RVVVectorBitsMax >= RVVVectorBitsMin &&
          "Minimum V extension vector length should not be larger than its "
          "maximum!");
   unsigned Max = std::max(RVVVectorBitsMin, RVVVectorBitsMax);
-  return PowerOf2Floor(Max < 128 ? 0 : Max);
+  return PowerOf2Floor((Max < 128 || Max > 65536) ? 0 : Max);
 }
 
 unsigned RISCVSubtarget::getMinRVVVectorSizeInBits() const {
   assert(hasStdExtV() &&
          "Tried to get vector length without V extension support!");
   assert((RVVVectorBitsMin == 0 ||
-          (RVVVectorBitsMin >= 128 && isPowerOf2_32(RVVVectorBitsMin))) &&
-         "V extension requires vector length to be at least 128 and a power of "
-         "2!");
+          (RVVVectorBitsMin >= 128 && RVVVectorBitsMax <= 65536 &&
+           isPowerOf2_32(RVVVectorBitsMin))) &&
+         "V extension requires vector length to be in the range of 128 to "
+         "65536 and a power of 2!");
   assert((RVVVectorBitsMax >= RVVVectorBitsMin || RVVVectorBitsMax == 0) &&
          "Minimum V extension vector length should not be larger than its "
          "maximum!");
   unsigned Min = RVVVectorBitsMin;
   if (RVVVectorBitsMax != 0)
     Min = std::min(RVVVectorBitsMin, RVVVectorBitsMax);
-  return PowerOf2Floor(Min < 128 ? 0 : Min);
+  return PowerOf2Floor((Min < 128 || Min > 65536) ? 0 : Min);
 }
 
 unsigned RISCVSubtarget::getMaxLMULForFixedLengthVectors() const {