[RISCV] Rewrite CheckInvalidVLENandLMUL to avoid floating point.

[craig.topper]

Summary

This avoids needing an FP value to represent LMUL.

[4vtomat]

LGTM, thanks!

clang/lib/Sema/SemaChecking.cpp

4479

Does the EGS here mean the ElemCount?
If it does, can we change the EGS in the comment to other name, since when I first see this comment, I just thought the EGS here means the argument name lol~

[craig.topper]

Revise coment, rename variable.

clang/lib/Sema/SemaChecking.cpp

 //===- SemaChecking.cpp - Extra Semantic Checking -------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
return Diag(TheCall->getBeginLoc(), diag::err_riscv_builtin_invalid_lmul)
          << Arg->getSourceRange();
 }
 
 static bool CheckInvalidVLENandLMUL(const TargetInfo &TI, CallExpr *TheCall,
                                     Sema &S, QualType Type, int EGW) {
   assert((EGW == 128 || EGW == 256) && "EGW can only be 128 or 256 bits");
 
   // LMUL * VLEN >= EGW
-  uint64_t ElemSize = Type->isRVVType(32, false) ? 32 : 64;
-  uint64_t ElemCount = Type->isRVVType(1) ? 1 :
-                       Type->isRVVType(2) ? 2 :
-                       Type->isRVVType(4) ? 4 :
-                       Type->isRVVType(8) ? 8 :
-                       16;
-  float Lmul = (float)(ElemSize * ElemCount) / llvm::RISCV::RVVBitsPerBlock;
-  uint64_t MinRequiredVLEN = std::max(EGW / Lmul, (float)ElemSize);
+  unsigned ElemSize = Type->isRVVType(32, false) ? 32 : 64;
+  unsigned MinElemCount = Type->isRVVType(1)   ? 1
+                          : Type->isRVVType(2) ? 2
+                          : Type->isRVVType(4) ? 4
+                          : Type->isRVVType(8) ? 8
+                                               : 16;
+
+  unsigned EGS = EGW / ElemSize;
+  // If EGS is less than or equal to the minimum number of elements we're done.
+  if (EGS <= MinElemCount)
+    return false;
+
+  // We need vscale to be at least this value.
+  unsigned VScaleFactor = EGS / MinElemCount;
+  // Vscale is VLEN/RVVBitsPerBlock.
+  unsigned MinRequiredVLEN = VScaleFactor * llvm::RISCV::RVVBitsPerBlock;
   std::string RequiredExt = "zvl" + std::to_string(MinRequiredVLEN) + "b";
   if (!TI.hasFeature(RequiredExt))
     return S.Diag(TheCall->getBeginLoc(),
         diag::err_riscv_type_requires_extension) << Type << RequiredExt;
 
   return false;
 }