[llvm-branch-commits] [clang] [llvm] [llvm] Introduce callee_type metadata (PR #87573)

[Prabhu Rajasekaran via llvm-branch-commits]

================
@@ -3423,6 +3424,17 @@ static void combineMetadata(Instruction *K, const Instruction *J,
                    MDNode::getMergedCallsiteMetadata(KCallSite, JCallSite));
   }
 
+  // Merge callee_type metadata.
+  // Handle separately to support cases where only one instruction has the
+  // metadata.
----------------
Prabhuk wrote:

I tried the following but could not get the simplifyCFG to produce that case:

```
define ptr @_Z10test_diff_fnptrsb(i1 zeroext %b) {
entry:
  %fn = alloca ptr
  %fn2 = alloca ptr
  store ptr @_Znwm, ptr %fn
  store ptr @_Znwm, ptr %fn2
  br i1 %b, label %if.then, label %if.else

if.then:                                          ; preds = %entry
  %call = call ptr %fn(i64 4), !callee_type !4
  br label %if.end

if.else:                                          ; preds = %entry
  %call1 = call ptr %fn2(i64 4), !callee_type !3
  br label %if.end

if.end:                                           ; preds = %if.else, %if.then
  %x.0 = phi ptr [ %call, %if.then ], [ %call1, %if.else ]
  ret ptr %x.0
}
declare ptr @_Znwm(i64)
```
`bin/opt -passes=simplifycfg -S < merge-callee-type-metadata.ll` was the command used.

This was the output:

```
define ptr @_Z10test_diff_fnptrsb(i1 zeroext %b) {
entry:
  %fn = alloca ptr, align 8
  %fn2 = alloca ptr, align 8
  store ptr @_Znwm, ptr %fn, align 8
  store ptr @_Znwm, ptr %fn2, align 8
  br i1 %b, label %if.then, label %if.else

if.then:                                          ; preds = %entry
  %call = call ptr %fn(i64 4), !callee_type !0
  br label %if.end

if.else:                                          ; preds = %entry
  %call1 = call ptr %fn2(i64 4), !callee_type !2
  br label %if.end

if.end:                                           ; preds = %if.else, %if.then
  %x.0 = phi ptr [ %call, %if.then ], [ %call1, %if.else ]
  ret ptr %x.0
}
```
I tried combinations where either %call and %call1 does not have callee_type. Tried both without callee_type as well. Only case where the call instructions get merged is when both instructions carried the same function ptr %fn.


https://github.com/llvm/llvm-project/pull/87573