[llvm] f883e75 - GlobalIFunc: Make allowed constant expressions stricter

[Matt Arsenault via llvm-commits]

Author: Matt Arsenault
Date: 2022-12-02T15:20:57-05:00
New Revision: f883e75497b610de81b3a6af106c976bb3c2bbb1

URL: https://github.com/llvm/llvm-project/commit/f883e75497b610de81b3a6af106c976bb3c2bbb1
DIFF: https://github.com/llvm/llvm-project/commit/f883e75497b610de81b3a6af106c976bb3c2bbb1.diff

LOG: GlobalIFunc: Make allowed constant expressions stricter

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).

Added: 
    llvm/test/Assembler/ifunc-stripPointerCastsAndAliases.ll
    llvm/test/Verifier/ifunc-opaque.ll

Modified: 
    llvm/lib/IR/Globals.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/IR/Globals.cpp b/llvm/lib/IR/Globals.cpp
index 7880369a2f98e..41b090a00ece6 100644
--- a/llvm/lib/IR/Globals.cpp
+++ b/llvm/lib/IR/Globals.cpp
@@ -584,9 +584,7 @@ void GlobalIFunc::eraseFromParent() {
 }
 
 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(

diff  --git a/llvm/test/Assembler/ifunc-stripPointerCastsAndAliases.ll b/llvm/test/Assembler/ifunc-stripPointerCastsAndAliases.ll
new file mode 100644
index 0000000000000..ae1b446e353ec
--- /dev/null
+++ b/llvm/test/Assembler/ifunc-stripPointerCastsAndAliases.ll
@@ -0,0 +1,23 @@
+; RUN: llvm-as < %s | llvm-dis | FileCheck %s
+
+; Check constantexprs which ifunc looks through to find the resolver
+; function.
+
+ at 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
+ at alias_resolver = internal alias i32 (i32), ptr @resolver
+
+; CHECK: @ifunc_resolver_is_alias = internal ifunc i32 (i32), ptr @alias_resolver
+ at 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
+}

diff  --git a/llvm/test/Verifier/ifunc-opaque.ll b/llvm/test/Verifier/ifunc-opaque.ll
new file mode 100644
index 0000000000000..349207b429ebd
--- /dev/null
+++ b/llvm/test/Verifier/ifunc-opaque.ll
@@ -0,0 +1,17 @@
+; 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
+ at ifunc_getelementptr = ifunc void (), ptr getelementptr (i8, ptr @resolver, i32 4)
+
+
+; Make sure nothing asserts on an unhandled constantexpr for the
+; resolver.
+
+; CHECK: IFunc must have a Function resolver
+; CHECK-NEXT: ptr @ifunc_shl
+ at ifunc_shl = ifunc void (), ptr inttoptr (i64 shl (i64 ptrtoint (ptr @resolver to i64), i64 4) to ptr)