[MergeFunctions] fix function attribute comparison in FunctionComparator

[eeckstein]

Summary

The comparison of AttributeSets stopped after seeing a matching type attribute.
Subsequent mismatching attributes were not detected.

This caused a crash in the swift compiler in case one of the AttributeSet contained a swifterror attribute (after the matching type attribute).

rdar://problem/70573980

[t.p.northover]

I think this looks fine.

[t.p.northover]

I've committed this for Erik as f7fe7ea24d3. Forgot to mention in the commit message that it was from him though, sorry.

llvm/lib/Transforms/Utils/FunctionComparator.cpp

for (; LI != LE && RI != RE; ++LI, ++RI) {
       Attribute LA = *LI;
       Attribute RA = *RI;
       if (LA.isTypeAttribute() && RA.isTypeAttribute()) {
         if (LA.getKindAsEnum() != RA.getKindAsEnum())
           return cmpNumbers(LA.getKindAsEnum(), RA.getKindAsEnum());
 
         Type *TyL = LA.getValueAsType();
         Type *TyR = RA.getValueAsType();
-        if (TyL && TyR)
-          return cmpTypes(TyL, TyR);
+        if (TyL && TyR) {
+          if (int Res = cmpTypes(TyL, TyR))
+            return Res;
+          continue;
+        }
 
         // Two pointers, at least one null, so the comparison result is
         // independent of the value of a real pointer.
-        return cmpNumbers((uint64_t)TyL, (uint64_t)TyR);
+        if (int Res = cmpNumbers((uint64_t)TyL, (uint64_t)TyR))
+          return Res;
+        continue;
       }
       if (LA < RA)
         return -1;
       if (RA < LA)
         return 1;
     }
     if (LI != LE)
       return 1;

llvm/test/Transforms/MergeFunc/mismatching-attr-crash.ll

+; RUN: opt -S -mergefunc %s | FileCheck %s
+
+; CHECK-LABEL: define void @foo
+; CHECK: call void %bc
+define void @foo(i8* byval %a0, i8* swiftself %a4) {
+entry:
+  %bc = bitcast i8* %a0 to void (i8*, i8*)*
+  call void %bc(i8* byval %a0, i8* swiftself %a4)
+  ret void
+}
+
+; CHECK-LABEL: define void @bar
+; CHECK: call void %bc
+define void @bar(i8* byval(i8) %a0, i8** swifterror %a4) {
+entry:
+  %bc = bitcast i8* %a0 to void (i8*, i8**)*
+  call void %bc(i8* byval(i8) %a0, i8** swifterror %a4)
+  ret void
+}
+
+