[GlobalOpt] Don't resolve aliased ifuncs with undefined resolvees. #96220
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Fixes llvm#96197. A global alias should always point to a definition. Ifuncs are definitions, so far so good. However an ifunc may be statically resolved to a function that is declared but not defined in the translation unit. With this patch we perform static resolution if: * the resolvee is defined * otherwise none of the ifunc users is a global alias
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@llvm/pr-subscribers-llvm-transforms Author: Alexandros Lamprineas (labrinea) ChangesFixes #96197. A global alias should always point to a definition. Ifuncs are definitions, so far so good. However an ifunc may be statically resolved to a function that is declared but not defined in the translation unit. With this patch we perform static resolution if:
Full diff: https://github.com/llvm/llvm-project/pull/96220.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index b7c6d25657bc0..411a8454bf18b 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -2458,7 +2458,9 @@ static bool OptimizeStaticIFuncs(Module &M) {
bool Changed = false;
for (GlobalIFunc &IF : M.ifuncs())
if (Function *Callee = hasSideeffectFreeStaticResolution(IF))
- if (!IF.use_empty()) {
+ if (!IF.use_empty() &&
+ (!Callee->isDeclaration() ||
+ none_of(IF.users(), [](User *U) { return isa<GlobalAlias>(U); }))) {
IF.replaceAllUsesWith(Callee);
NumIFuncsResolved++;
Changed = true;
diff --git a/llvm/test/Transforms/GlobalOpt/resolve-static-ifunc.ll b/llvm/test/Transforms/GlobalOpt/resolve-static-ifunc.ll
index 2a1717304fb4c..de087343208c7 100644
--- a/llvm/test/Transforms/GlobalOpt/resolve-static-ifunc.ll
+++ b/llvm/test/Transforms/GlobalOpt/resolve-static-ifunc.ll
@@ -7,11 +7,15 @@ target triple = "aarch64-unknown-linux-gnu"
@trivial.ifunc = internal ifunc void (), ptr @trivial.resolver
;.
; CHECK: @unknown_condition = external local_unnamed_addr global i1
+; CHECK: @alias_decl = weak_odr alias void (), ptr @aliased_decl.ifunc
+; CHECK: @alias_def = weak_odr alias void (), ptr @aliased_def._Msimd
; CHECK: @external_ifunc.ifunc = dso_local ifunc void (), ptr @external_ifunc.resolver
; CHECK: @complex.ifunc = internal ifunc void (), ptr @complex.resolver
; CHECK: @sideeffects.ifunc = internal ifunc void (), ptr @sideeffects.resolver
; CHECK: @interposable_ifunc.ifunc = internal ifunc void (), ptr @interposable_ifunc.resolver
; CHECK: @interposable_resolver.ifunc = weak ifunc void (), ptr @interposable_resolver.resolver
+; CHECK: @aliased_decl.ifunc = weak_odr ifunc void (), ptr @aliased_decl.resolver
+; CHECK: @aliased_def.ifunc = weak_odr ifunc void (), ptr @aliased_def.resolver
;.
define ptr @trivial.resolver() {
ret ptr @trivial._Msimd
@@ -89,6 +93,20 @@ define void @interposable_resolver.default() {
ret void
}
+@alias_decl = weak_odr alias void (), ptr @aliased_decl.ifunc
+@aliased_decl.ifunc = weak_odr ifunc void (), ptr @aliased_decl.resolver
+declare void @aliased_decl._Msimd()
+define ptr @aliased_decl.resolver() {
+ ret ptr @aliased_decl._Msimd
+}
+
+@alias_def = weak_odr alias void (), ptr @aliased_def.ifunc
+@aliased_def.ifunc = weak_odr ifunc void (), ptr @aliased_def.resolver
+define void @aliased_def._Msimd() { ret void }
+define ptr @aliased_def.resolver() {
+ ret ptr @aliased_def._Msimd
+}
+
define void @caller() {
; CHECK-LABEL: define void @caller() local_unnamed_addr {
; CHECK-NEXT: call void @trivial._Msimd()
@@ -97,6 +115,8 @@ define void @caller() {
; CHECK-NEXT: call void @sideeffects.ifunc()
; CHECK-NEXT: call void @interposable_ifunc.ifunc()
; CHECK-NEXT: call void @interposable_resolver.ifunc()
+; CHECK-NEXT: call void @aliased_decl.ifunc()
+; CHECK-NEXT: call void @aliased_def._Msimd()
; CHECK-NEXT: ret void
;
call void @trivial.ifunc()
@@ -105,5 +125,7 @@ define void @caller() {
call void @sideeffects.ifunc()
call void @interposable_ifunc.ifunc()
call void @interposable_resolver.ifunc()
+ call void @aliased_decl.ifunc()
+ call void @aliased_def.ifunc()
ret void
}
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labrinea
changed the title
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/56/builds/582 Here is the relevant piece of the build log for the reference: |
AlexisPerry
pushed a commit
to llvm-project-tlp/llvm-project
that referenced
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Jul 9, 2024
…lvm#96220) Fixes llvm#96197. A global alias should always point to a definition. Ifuncs are definitions, so far so good. However an ifunc may be statically resolved to a function that is declared but not defined in the translation unit. With this patch we perform static resolution if: * the resolvee is defined, else if * none of the ifunc users is a global alias
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Fixes #96197.
A global alias should always point to a definition. Ifuncs are definitions, so far so good. However an ifunc may be statically resolved to a function that is declared but not defined in the translation unit.
With this patch we perform static resolution if: