[MergeFunc] Allow merging identical vararg functions using aliases
Thanks to Nikita Popov for pointing out this missed case.
This is a follow-up to r351411, which disabled function merging for
vararg functions outright due to a miscompile (see llvm.org/PR40345).
Differential Revision: https://reviews.llvm.org/D56865
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351624 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/IPO/MergeFunctions.cpp b/lib/Transforms/IPO/MergeFunctions.cpp
index 26b204f..f143b25 100644
--- a/lib/Transforms/IPO/MergeFunctions.cpp
+++ b/lib/Transforms/IPO/MergeFunctions.cpp
@@ -281,8 +281,8 @@
// Replace G with an alias to F (deleting function G)
void writeAlias(Function *F, Function *G);
- // Replace G with an alias to F if possible, or a thunk to F if
- // profitable. Returns false if neither is the case.
+ // Replace G with an alias to F if possible, or a thunk to F if possible.
+ // Returns false if neither is the case.
bool writeThunkOrAlias(Function *F, Function *G);
/// Replace function F with function G in the function tree.
@@ -385,8 +385,7 @@
/// Check whether \p F is eligible for function merging.
static bool isEligibleForMerging(Function &F) {
- return !F.isDeclaration() && !F.hasAvailableExternallyLinkage() &&
- !F.isVarArg();
+ return !F.isDeclaration() && !F.hasAvailableExternallyLinkage();
}
bool MergeFunctions::runOnModule(Module &M) {
@@ -660,12 +659,16 @@
LLVM_DEBUG(dbgs() << " }\n");
}
-// Don't merge tiny functions using a thunk, since it can just end up
-// making the function larger.
-static bool isThunkProfitable(Function * F) {
+/// Whether this function may be replaced by a forwarding thunk.
+static bool canCreateThunkFor(Function *F) {
+ if (F->isVarArg())
+ return false;
+
+ // Don't merge tiny functions using a thunk, since it can just end up
+ // making the function larger.
if (F->size() == 1) {
if (F->front().size() <= 2) {
- LLVM_DEBUG(dbgs() << "isThunkProfitable: " << F->getName()
+ LLVM_DEBUG(dbgs() << "canCreateThunkFor: " << F->getName()
<< " is too small to bother creating a thunk for\n");
return false;
}
@@ -793,7 +796,7 @@
writeAlias(F, G);
return true;
}
- if (isThunkProfitable(F)) {
+ if (canCreateThunkFor(F)) {
writeThunk(F, G);
return true;
}
@@ -808,9 +811,9 @@
// Both writeThunkOrAlias() calls below must succeed, either because we can
// create aliases for G and NewF, or because a thunk for F is profitable.
// F here has the same signature as NewF below, so that's what we check.
- if (!isThunkProfitable(F) && (!canCreateAliasFor(F) || !canCreateAliasFor(G))) {
+ if (!canCreateThunkFor(F) &&
+ (!canCreateAliasFor(F) || !canCreateAliasFor(G)))
return;
- }
// Make them both thunks to the same internal function.
Function *NewF = Function::Create(F->getFunctionType(), F->getLinkage(),
diff --git a/test/Transforms/MergeFunc/va_arg.ll b/test/Transforms/MergeFunc/va_arg.ll
index eb49a72..1a48a63 100644
--- a/test/Transforms/MergeFunc/va_arg.ll
+++ b/test/Transforms/MergeFunc/va_arg.ll
@@ -1,14 +1,18 @@
; RUN: opt -S -mergefunc < %s | FileCheck %s
+; RUN: opt -S -mergefunc -mergefunc-use-aliases < %s | FileCheck %s -check-prefix=ALIAS
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
+; ALIAS: @_Z9simple_vaPKcz = unnamed_addr alias void (i8*, ...), void (i8*, ...)* @_Z10simple_va2PKcz
+; ALIAS-NOT: @_Z9simple_vaPKcz
+
%struct.__va_list_tag = type { i32, i32, i8*, i8* }
; CHECK-LABEL: define {{.*}}@_Z9simple_vaPKcz
; CHECK: call void @llvm.va_start
; CHECK: call void @llvm.va_end
-define dso_local void @_Z9simple_vaPKcz(i8* nocapture readnone, ...) local_unnamed_addr {
+define dso_local void @_Z9simple_vaPKcz(i8* nocapture readnone, ...) unnamed_addr {
%2 = alloca [1 x %struct.__va_list_tag], align 16
%3 = bitcast [1 x %struct.__va_list_tag]* %2 to i8*
call void @llvm.va_start(i8* nonnull %3)
@@ -54,7 +58,7 @@
; CHECK-LABEL: define {{.*}}@_Z10simple_va2PKcz
; CHECK: call void @llvm.va_start
; CHECK: call void @llvm.va_end
-define dso_local void @_Z10simple_va2PKcz(i8* nocapture readnone, ...) local_unnamed_addr {
+define dso_local void @_Z10simple_va2PKcz(i8* nocapture readnone, ...) unnamed_addr {
%2 = alloca [1 x %struct.__va_list_tag], align 16
%3 = bitcast [1 x %struct.__va_list_tag]* %2 to i8*
call void @llvm.va_start(i8* nonnull %3)
