[PATCH] D114581: [RISCV] Fix a crash in decoding LMUL in VTYPE

[Ben Shi via Phabricator via llvm-commits]

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This patch fixes a crash when using "llvm-objdump -D --mattr=+experimental-v"
against an OBJ file which happens to keep a word that can be decoded to
VSETVLI but contains LMUL=4 which is reserved.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D114581

Files:
  llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.cpp
  llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
  llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
  llvm/test/tools/llvm-objdump/RISCV/Inputs/vsetvli.o
  llvm/test/tools/llvm-objdump/RISCV/vsetvli.test


Index: llvm/test/tools/llvm-objdump/RISCV/vsetvli.test
===================================================================
--- /dev/null
+++ llvm/test/tools/llvm-objdump/RISCV/vsetvli.test
@@ -0,0 +1,5 @@
+// RUN: llvm-objdump -D --mattr=+experimental-v %p/Inputs/vsetvli.o | FileCheck --check-prefix=CHECK %s
+
+# CHECK: 0: d7 75 85 01 vsetvli a1, a0, e64, m1, tu, mu
+# CHECK: 4: d7 75 c5 01 vsetvli a1, a0, e64, <reserved LMUL>, tu, mu
+# CHECK: 8: d7 75 d5 01 vsetvli a1, a0, e64, mf8, tu, mu
Index: llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
+++ llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
@@ -409,6 +409,7 @@
       unsigned LMulVal;
       bool Fractional;
       std::tie(LMulVal, Fractional) = RISCVVType::decodeVLMUL(LMul);
+      assert(LMulVal != 0 && "Reserved LMUL value");
       assert(!Fractional && "It is impossible be fractional lmul here.");
       if (forwardCopyWillClobberTuple(DstEncoding, SrcEncoding, NF * LMulVal)) {
         I = NF - 1;
Index: llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
+++ llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
@@ -155,6 +155,7 @@
     unsigned LMul;
     bool Fractional;
     std::tie(LMul, Fractional) = RISCVVType::decodeVLMUL(VLMul);
+    assert(LMul != 0 && "Reserved LMUL value");
 
     // Convert LMul to a fixed point value with 3 fractional bits.
     LMul = Fractional ? (8 / LMul) : (LMul * 8);
Index: llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.cpp
===================================================================
--- llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.cpp
+++ llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.cpp
@@ -138,7 +138,7 @@
 std::pair<unsigned, bool> RISCVVType::decodeVLMUL(RISCVII::VLMUL VLMUL) {
   switch (VLMUL) {
   default:
-    llvm_unreachable("Unexpected LMUL value!");
+    return std::make_pair(0, false);
   case RISCVII::VLMUL::LMUL_1:
   case RISCVII::VLMUL::LMUL_2:
   case RISCVII::VLMUL::LMUL_4:
@@ -159,11 +159,12 @@
   bool Fractional;
   std::tie(LMul, Fractional) = decodeVLMUL(getVLMUL(VType));
 
-  if (Fractional)
-    OS << ", mf";
+  if (LMul == 0)
+    OS << ", <reserved LMUL>";
+  else if (Fractional)
+    OS << ", mf" << LMul;
   else
-    OS << ", m";
-  OS << LMul;
+    OS << ", m" << LMul;
 
   if (isTailAgnostic(VType))
     OS << ", ta";


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