GlobalIFunc: Make allowed constant expressions stricter

[arsenm]

Summary

This was allowing getelementptr with offsets, which doesn't make
sense. My initial attempt to use stripPointerCasts broke a few tests
involving aliases; add a new targeted verifier test for aliases.

This also provides the fix from D138537 for free, and also adds
support for addrspacecast (D138538) for free. Merge the tests in from
those.

I'm not really sure why findBaseObject exists; it seems redundant with
stripPointerCasts* (I'm also not really sure why getelementptrs are
allowed off of functions).

[MaskRay]

llvm/test/Assembler/ifunc-addrspacecast.ll

1 ↗

(On Diff #477676)

These tests test similar properties. Consider using split-file.

[arsenm]

Merge tests. split-file wouldn't really help here

[aeubanks]

seems reasonable

[MaskRay]

I still think it's useful to group tests, so that readers can get all invalid cases by reading one file, instead of many

[arsenm]

f883e75497b610de81b3a6af106c976bb3c2bbb1 with merged error tests. Assembler error tests can't be split because the assembler doesn't continue past the first, but these are handled in the verifier, so moved there

[MaskRay]

I didn't request. I meant that you can improve clarify with RUN: rm -rf %t && split-file %s %t && cd %t (optional cd %t) https://llvm.org/docs/TestingGuide.html#extra-files

llvm/lib/IR/Globals.cpp

void GlobalIFunc::removeFromParent() {
   getParent()->getIFuncList().remove(getIterator());
 }
 
 void GlobalIFunc::eraseFromParent() {
   getParent()->getIFuncList().erase(getIterator());
 }
 
 const Function *GlobalIFunc::getResolverFunction() const {
-  DenseSet<const GlobalAlias *> Aliases;
-  return dyn_cast<Function>(
-      findBaseObject(getResolver(), Aliases, [](const GlobalValue &) {}));
+  return dyn_cast<Function>(getResolver()->stripPointerCastsAndAliases());
 }
 
 void GlobalIFunc::applyAlongResolverPath(
     function_ref<void(const GlobalValue &)> Op) const {
   DenseSet<const GlobalAlias *> Aliases;
   findBaseObject(getResolver(), Aliases, Op);
 }

llvm/test/Assembler/ifunc-stripPointerCastsAndAliases.ll

+; RUN: llvm-as < %s | llvm-dis | FileCheck %s
+
+; Check constantexprs which ifunc looks through to find the resolver
+; function.
+
+@ifunc_addrspacecast_as1_to_as0 = ifunc void (), ptr addrspacecast (ptr addrspace(1) @resolver_as1 to ptr)
+
+; CHECK: @alias_resolver = internal alias i32 (i32), ptr @resolver
+@alias_resolver = internal alias i32 (i32), ptr @resolver
+
+; CHECK: @ifunc_resolver_is_alias = internal ifunc i32 (i32), ptr @alias_resolver
+@ifunc_resolver_is_alias = internal ifunc i32 (i32), ptr @alias_resolver
+
+
+; CHECK: define ptr @resolver_as1() addrspace(1) {
+define ptr @resolver_as1() addrspace(1) {
+  ret ptr null
+}
+
+; CHECK: define internal ptr @resolver() {
+define internal ptr @resolver() {
+  ret ptr null
+}

llvm/test/Assembler/ifunc-unhandled-constantexpr.ll

+; RUN: not llvm-as < %s 2>&1 | FileCheck %s
+
+; Make sure nothing asserts on an unhandled constantexpr for the
+; resolver.
+
+; CHECK: IFunc must have a Function resolver
+; CHECK-NEXT: ptr @ifunc_shl
+@ifunc_shl = ifunc void (), ptr inttoptr (i64 shl (i64 ptrtoint (ptr @resolver to i64), i64 4) to ptr)
+
+define ptr @resolver() {
+  ret ptr null
+}

llvm/test/Verifier/ifunc-opaque.ll

+; RUN:  not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
+
+define ptr @resolver() {
+  ret ptr null
+}
+
+; CHECK: IFunc must have a Function resolver
+; CHECK-NEXT: ptr @ifunc_getelementptr
+@ifunc_getelementptr = ifunc void (), ptr getelementptr (i8, ptr @resolver, i32 4)