[FunctionAttr] Invalidate callers with mismatching signature (llvm#154289)

If FunctionAttrs infers additional attributes on a function, it also
invalidates analysis on callers of that function. The way it does this
right now limits this to calls with matching signature. However, the
function attributes will also be used when the signatures do not match.
Use getCalledOperand() to avoid a signature check.

This is not a correctness fix, just improves analysis quality. I noticed
this due to
llvm#144497 (comment),
where LICM ends up with a stale MemoryDef that could be a MemoryUse
(which is a bug in LICM, but still non-optimal).

Author: nikic

llvm/lib/Transforms/IPO/FunctionAttrs.cpp

@@ -2328,7 +2328,7 @@ PreservedAnalyses PostOrderFunctionAttrsPass::run(LazyCallGraph::SCC &C,
     // through function attributes.
     for (auto *U : Changed->users()) {
       if (auto *Call = dyn_cast<CallBase>(U)) {
-        if (Call->getCalledFunction() == Changed)
+        if (Call->getCalledOperand() == Changed)
           FAM.invalidate(*Call->getFunction(), FuncPA);
       }
     }

llvm/test/Transforms/FunctionAttrs/mismatched-signature-invalidation.ll

@@ -0,0 +1,31 @@
+; RUN: opt -disable-output -passes="function(print<memoryssa>),cgscc(function-attrs),function(print<memoryssa>)" < %s 2>&1 | FileCheck %s
+
+@g = external global i16
+
+define i16 @fn() {
+  %v = load i16, ptr @g
+  ret i16 %v
+}
+
+declare void @fn2(i16)
+
+; CHECK-LABEL: MemorySSA for function: test
+; CHECK: 1 = MemoryDef(3)
+; CHECK-NEXT: %call = call i16 @fn(i32 0)
+
+; CHECK-LABEL: MemorySSA for function: test
+; CHECK: MemoryUse(2)
+; CHECK-NEXT: %call = call i16 @fn(i32 0)
+
+define void @test() {
+entry:
+  br label %loop
+
+loop:
+  %call = call i16 @fn(i32 0) ; intentional signature mismatch
+  call void @fn2(i16 %call)
+  br i1 false, label %loop, label %exit
+
+exit:
+  ret void
+}