[EVM] Don't emit JUMPDEST in entry point of bytecode

We don't need to emit JUMPDEST instruction in the first
BB of the __entry function.

Signed-off-by: Vladimir Radosavljevic <[email protected]>

Author: vladimirradosavljevic

llvm/lib/Target/EVM/EVMAsmPrinter.cpp

@@ -127,9 +127,18 @@ void EVMAsmPrinter::emitFunctionBodyEnd() { FirstFunctIsHandled = true; }
 void EVMAsmPrinter::emitBasicBlockStart(const MachineBasicBlock &MBB) {
   AsmPrinter::emitBasicBlockStart(MBB);
 
+  // If this is __entry function, we don't need to emit JUMPDEST
+  // instruction in the first basic block, as it is the entry point
+  // of the EVM bytecode.
+  auto IsEntryPoint = [this](const MachineBasicBlock &MBB) {
+    return !FirstFunctIsHandled && &MBB == &MF->front() &&
+           MF->getName() == "__entry";
+  };
+
   // Emit JUMPDEST instruction at the beginning of the basic block, if
   // this is not a block that is only reachable by fallthrough.
-  if (!EVMKeepRegisters && !AsmPrinter::isBlockOnlyReachableByFallthrough(&MBB))
+  if (!EVMKeepRegisters && !IsEntryPoint(MBB) &&
+      !AsmPrinter::isBlockOnlyReachableByFallthrough(&MBB))
     emitJumpDest();
 }
 

llvm/test/CodeGen/EVM/jumpdest-in-entry-point.ll

@@ -9,7 +9,6 @@ declare void @llvm.evm.return(ptr addrspace(1), i256)
 define void @__entry() noreturn {
 ; CHECK-LABEL: __entry:
 ; CHECK:       ; %bb.0: ; %entry
-; CHECK-NEXT:    JUMPDEST
 ; CHECK-NEXT:    PUSH0
 ; CHECK-NEXT:    MLOAD
 ; CHECK-NEXT:    DUP1