Don't merge tiny functions.

It's silly to merge functions like these:

define void @foo(i32 %x) {
  ret void
}

define void @bar(i32 %x) {
  ret void
}

to get

define void @bar(i32) {
  tail call void @foo(i32 %0)
  ret void
}

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191786 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/IPO/MergeFunctions.cpp b/lib/Transforms/IPO/MergeFunctions.cpp
index 0f09b9026ebf53fb29129d6bb567cef75b96939d..7e4c1668455567d9d4f944af97e21c5750380420 100644 (file)
--- a/lib/Transforms/IPO/MergeFunctions.cpp
+++ b/lib/Transforms/IPO/MergeFunctions.cpp
@@ -836,6 +836,18 @@ bool MergeFunctions::insert(ComparableFunction &NewF) {
 
   const ComparableFunction &OldF = *Result.first;
 
+  // Don't merge tiny functions, since it can just end up making the function
+  // larger.
+  // FIXME: Should still merge them if they are unnamed_addr and produce an
+  // alias.
+  if (NewF.getFunc()->size() == 1) {
+    if (NewF.getFunc()->front().size() <= 2) {
+      DEBUG(dbgs() << NewF.getFunc()->getName()
+            << " is to small to bother merging\n");
+      return false;
+    }
+  }
+
   // Never thunk a strong function to a weak function.
   assert(!OldF.getFunc()->mayBeOverridden() ||
          NewF.getFunc()->mayBeOverridden());

diff --git a/test/Transforms/MergeFunc/merge-ptr-and-int.ll b/test/Transforms/MergeFunc/merge-ptr-and-int.ll
index 7a178a211392b8182fccee4d1e9703af17ce6619..4e887cec9065894b8e1deb488f0e786d3d832541 100644 (file)
--- a/test/Transforms/MergeFunc/merge-ptr-and-int.ll
+++ b/test/Transforms/MergeFunc/merge-ptr-and-int.ll
@@ -1,18 +1,27 @@
 ; RUN: opt -S -mergefunc < %s | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 
-; CHECK-LABEL: f0
+
+declare void @stuff()
+
+; CHECK-LABEL: @f0(
 define void @f0(i64 %p0) {
 entry:
+  call void @stuff()
+  call void @stuff()
+  call void @stuff()
   ret void
 }
 
-; CHECK-LABEL: f1
+; CHECK-LABEL: @f1(
 ; CHECK: ptrtoint i64*
 ; CHECK: tail call void @f0(i64
 
 define void @f1(i64* %p0) {
 entry:
+  call void @stuff()
+  call void @stuff()
+  call void @stuff()
   ret void
 }
 

diff --git a/test/Transforms/MergeFunc/too-small.ll b/test/Transforms/MergeFunc/too-small.ll
new file mode 100644 (file)
index 0000000..1a526ff
--- /dev/null
+++ b/test/Transforms/MergeFunc/too-small.ll
@@ -0,0 +1,14 @@
+; RUN: opt -S -mergefunc < %s | FileCheck %s
+
+define void @foo(i32 %x) {
+; CHECK-LABEL: @foo(
+; CHECK-NOT: call
+  ret void
+}
+
+define void @bar(i32 %x) {
+; CHECK-LABEL: @bar(
+; CHECK-NOT: call
+  ret void
+}
+