[llvm] 32d5351 - BPF: Emit an error for illegal LD_imm64 insn when LLVM_ENABLE_ASSERTI… (#74035)

[via llvm-commits]

Author: yonghong-song
Date: 2023-12-07T11:29:40-08:00
New Revision: 32d535195ec5d9b0caf03fee13f796fc8c66a79f

URL: https://github.com/llvm/llvm-project/commit/32d535195ec5d9b0caf03fee13f796fc8c66a79f
DIFF: https://github.com/llvm/llvm-project/commit/32d535195ec5d9b0caf03fee13f796fc8c66a79f.diff

LOG: BPF: Emit an error for illegal LD_imm64 insn when LLVM_ENABLE_ASSERTI… (#74035)

…ONS=OFF

Jose reported an issue ([1]) where for the below illegal asm code
```
  r0 = 1 + w3 ll
```
clang actually supports it and generates the object code.

Further investigation finds that clang actually intends to reject the
above code as well but only when the clang is built with
LLVM_ENABLE_ASSERTIONS=ON.

I later found that clang16 (built by redhat and centos) in fedora system
has the same issue since they also have LLVM_ENABLE_ASSERTIONS=OFF
([2]).

So let BPF backend report an error for the above case regardless of the
LLVM_ENABLE_ASSERTIONS setting.

  [1] https://lore.kernel.org/bpf/87leahx2xh.fsf@oracle.com/#t
[2]
https://lore.kernel.org/bpf/840e33ec-ea4c-4b55-bda1-0be8d1e0324f@linux.dev/

Co-authored-by: Yonghong Song <yonghong.song at linux.dev>

Added: 
    

Modified: 
    llvm/lib/Target/BPF/MCTargetDesc/BPFInstPrinter.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/BPF/MCTargetDesc/BPFInstPrinter.cpp b/llvm/lib/Target/BPF/MCTargetDesc/BPFInstPrinter.cpp
index 15ab55f95e69b..c266538bec736 100644
--- a/llvm/lib/Target/BPF/MCTargetDesc/BPFInstPrinter.cpp
+++ b/llvm/lib/Target/BPF/MCTargetDesc/BPFInstPrinter.cpp
@@ -36,15 +36,16 @@ void BPFInstPrinter::printInst(const MCInst *MI, uint64_t Address,
 }
 
 static void printExpr(const MCExpr *Expr, raw_ostream &O) {
-#ifndef NDEBUG
   const MCSymbolRefExpr *SRE;
 
   if (const MCBinaryExpr *BE = dyn_cast<MCBinaryExpr>(Expr))
     SRE = dyn_cast<MCSymbolRefExpr>(BE->getLHS());
   else
     SRE = dyn_cast<MCSymbolRefExpr>(Expr);
-  assert(SRE && "Unexpected MCExpr type.");
+  if (!SRE)
+    report_fatal_error("Unexpected MCExpr type.");
 
+#ifndef NDEBUG
   MCSymbolRefExpr::VariantKind Kind = SRE->getKind();
 
   assert(Kind == MCSymbolRefExpr::VK_None);