[LLParser] Delete temporary CallInst when error occurs in ParseCall

[qiucf]

Summary

Below is the motivating test case:

define dso_local i64 @test_lrint_fast(double %d) local_unnamed_addr {
entry:
  %0 = call fast i64 @llvm.lrint.i64.f64(double %d)
  ret i64 %0
}

declare i64 @llvm.lrint.i64.f64(double)

Compile it with llc, we see:

While deleting: double %
Use still stuck around after Def is destroyed:  <badref> = call addrspace(0) i64 @llvm.lrint.i64.f64(double %0)
Assertion failed: (materialized_use_empty() && "Uses remain when a value is destroyed!"), function ~Value, file llvm-project/llvm/lib/IR/Value.cpp, line 96.

The reason is we still have an undeleted value referencing the argument.

[arsenm]

Needs test

[spatel]

Should we fix the definition of FPMathOperator and/or change the IR verifier instead? How did that call acquire FMF in the first place?

[qiucf]

Add a test

[qiucf]

In D78355#1989054, @spatel wrote:

Should we fix the definition of FPMathOperator and/or change the IR verifier instead? How did that call acquire FMF in the first place?

It's not correct IR. However, that's a crash we'd like to avoid.

I was not clear we can't add FMF to functions returning int. We can only add enable-unsafe-fp-math to use native instruction instead of libcall (at least, on PPC), but the option is deprecated. That seems to be an issue.

[qiucf]

Ping

[spatel]

It's an improvement in the crash experience, so that's ok with me. But see if @arsenm agrees.
Still need to decide how to apply/verify FMF in general.

[qiucf]

Ping.. @arsenm

[arsenm]

LGTM

llvm/lib/AsmParser/LLParser.cpp

   AttributeList PAL =
       AttributeList::get(Context, AttributeSet::get(Context, FnAttrs),
                          AttributeSet::get(Context, RetAttrs), Attrs);
 
   CallInst *CI = CallInst::Create(Ty, Callee, Args, BundleList);
   CI->setTailCallKind(TCK);
   CI->setCallingConv(CC);
   if (FMF.any()) {
-    if (!isa<FPMathOperator>(CI))
+    if (!isa<FPMathOperator>(CI)) {
+      CI->deleteValue();
       return Error(CallLoc, "fast-math-flags specified for call without "
                    "floating-point scalar or vector return type");
+    }
     CI->setFastMathFlags(FMF);
   }
   CI->setAttributes(PAL);
   ForwardRefAttrGroups[CI] = FwdRefAttrGrps;
   Inst = CI;
   return false;
 }