[RISCV][MC] Reject bare symbols for the simm6 and simm6nonzero operand types

Summary:
Fixed assertions due to invalid fixup when encoding compressed instructions
 (c.addi, c.addiw, c.li, c.andi) with bare symbols with/without modifiers.
  This matches GAS behavior as well.

This bug was uncovered by a LLVM MC Disassembler Protocol Buffer Fuzzer
for the RISC-V assembly language.

Reviewers: asb

Reviewed By: asb

Subscribers: rbar, johnrusso, simoncook, sabuasal, niosHD, kito-cheng, shiva0217, zzheng, edward-jones, mgrang, rogfer01, MartinMosbeck, brucehoult, the_o, rkruppe, PkmX, jocewei, asb

Differential Revision: https://reviews.llvm.org/D52005

llvm-svn: 342160

1 files changed, 4 insertions, 14 deletions

diff --git a/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp b/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
index 3e469c89369..7b010f54b0b 100644
--- a/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
+++ b/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
@@ -326,14 +326,9 @@ public:
       return false;
     RISCVMCExpr::VariantKind VK;
     int64_t Imm;
-    bool IsValid;
     bool IsConstantImm = evaluateConstantImm(Imm, VK);
-    if (!IsConstantImm)
-      IsValid = RISCVAsmParser::classifySymbolRef(getImm(), VK, Imm);
-    else
-      IsValid = isInt<6>(Imm);
-    return IsValid &&
-           (VK == RISCVMCExpr::VK_RISCV_None || VK == RISCVMCExpr::VK_RISCV_LO);
+    return IsConstantImm && isInt<6>(Imm) &&
+           VK == RISCVMCExpr::VK_RISCV_None;
   }
 
   bool isSImm6NonZero() const {
@@ -341,14 +336,9 @@ public:
       return false;
     RISCVMCExpr::VariantKind VK;
     int64_t Imm;
-    bool IsValid;
     bool IsConstantImm = evaluateConstantImm(Imm, VK);
-    if (!IsConstantImm)
-      IsValid = RISCVAsmParser::classifySymbolRef(getImm(), VK, Imm);
-    else
-      IsValid = ((Imm != 0) && isInt<6>(Imm));
-    return IsValid &&
-           (VK == RISCVMCExpr::VK_RISCV_None || VK == RISCVMCExpr::VK_RISCV_LO);
+    return IsConstantImm && isInt<6>(Imm) && (Imm != 0) &&
+           VK == RISCVMCExpr::VK_RISCV_None;
   }
 
   bool isCLUIImm() const {