Add delete to fix resource leak in llc.cpp

[XinWang10]

Summary

From line 693 in file llc.cpp, it uses new operator to creates a ModulePass
and assigned to MMIWP. If the condition after take the true branch, it has
chance to go in to line 702 or line 709, the function will return without
cleaning the memory.
The second issue existed for the same reason, the ref TPC get the pointer
created from LLVMTM.createPassConfig, and will leak memory if goes into
line 709.
This patch uses delete in the issued branch.

[craig.topper]

llvm/tools/llc/llc.cpp

702

Why is it only a leak on these paths? The are other return 1 in this function.

Can we use std::unique_ptr where these are created?

[XinWang10]

llvm/tools/llc/llc.cpp

702

1. MMIWP and TPC will be maintained by PM here at line 717, 718. I remember that PM's destructor will handle them.
2. MMIWP and TPC will be used as parameters for function like PM.add or arget->addPassesToEmitFile() in line 727, if we use unique_ptr, we need to handle more complicated issues.

[craig.topper]

llvm/tools/llc/llc.cpp

702

Can we release the unique_ptr when we hand it over to PM?

[XinWang10]

llvm/tools/llc/llc.cpp

702

Yes we can. If it its preferred, will take a try.

[XinWang10]

llvm/tools/llc/llc.cpp

702

I took a try and find if we use unique_ptr instead and release the unique_ptr when we hand it over to PM, we can not handle it well after PM.add(MMIWP), at line 734 and 737 we still use it.
So I think it's not proper here to use unique_ptr.

[craig.topper]

LGTM

llvm/tools/llc/llc.cpp

MachineModuleInfoWrapperPass *MMIWP =
         new MachineModuleInfoWrapperPass(&LLVMTM);
 
     // Construct a custom pass pipeline that starts after instruction
     // selection.
     if (!getRunPassNames().empty()) {
       if (!MIR) {
         WithColor::warning(errs(), argv[0])
             << "run-pass is for .mir file only.\n";
+        delete MMIWP;
         return 1;
       }
-      TargetPassConfig &TPC = *LLVMTM.createPassConfig(PM);
+      TargetPassConfig *PTPC = LLVMTM.createPassConfig(PM);
+      TargetPassConfig &TPC = *PTPC;
       if (TPC.hasLimitedCodeGenPipeline()) {
         WithColor::warning(errs(), argv[0])
             << "run-pass cannot be used with "
             << TPC.getLimitedCodeGenPipelineReason(" and ") << ".\n";
+        delete PTPC;
+        delete MMIWP;
         return 1;
       }
 
       TPC.setDisableVerify(NoVerify);
       PM.add(&TPC);
       PM.add(MMIWP);
       TPC.printAndVerify("");
       for (const std::string &RunPassName : getRunPassNames()) {