[PATCH] SimplifyCFG: Don't duplicate calls to functions marked noduplicate

[Tom Stellard]

On Thu, Oct 17, 2013 at 12:44:13PM -0700, Matt Arsenault wrote:
> On 10/16/2013 01:54 PM, Tom Stellard wrote:
> >From: Tom Stellard <thomas.stellard at amd.com>
> >
> >
> >+    if (CI->hasFnAttr(Attribute::NoDuplicate))
> >+
> How about using CI->cannotDuplicate()?
> 

Attached is an updated version of the patch with this change.

-Tom
-------------- next part --------------
>From c7f46ffcb620fbe2fc1c66e6a066c06a7ec215fe Mon Sep 17 00:00:00 2001
From: Tom Stellard <thomas.stellard at amd.com>
Date: Wed, 16 Oct 2013 09:18:53 -0700
Subject: [PATCH] SimplifyCFG: Don't duplicate calls to functions marked
 noduplicate v2

v2:
  - Use CI->cannotDuplicate()
---
 lib/Transforms/Utils/SimplifyCFG.cpp            | 15 ++++++++++
 test/Transforms/SimplifyCFG/attr-noduplicate.ll | 37 +++++++++++++++++++++++++
 2 files changed, 52 insertions(+)
 create mode 100644 test/Transforms/SimplifyCFG/attr-noduplicate.ll

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 0e56904..1d7c42f 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1557,6 +1557,19 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB) {
   return true;
 }
 
+/// \returns True if this block contains a CallInst with the NoDuplicate
+/// attribute.
+static bool HasNoDuplicateCall(const BasicBlock *BB) {
+  for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
+    const CallInst *CI = dyn_cast<CallInst>(I);
+    if (!CI)
+      continue;
+    if (CI->cannotDuplicate())
+      return true;
+  }
+  return false;
+}
+
 /// BlockIsSimpleEnoughToThreadThrough - Return true if we can thread a branch
 /// across this block.
 static bool BlockIsSimpleEnoughToThreadThrough(BasicBlock *BB) {
@@ -1604,6 +1617,8 @@ static bool FoldCondBranchOnPHI(BranchInst *BI, const DataLayout *TD) {
   // Now we know that this block has multiple preds and two succs.
   if (!BlockIsSimpleEnoughToThreadThrough(BB)) return false;
 
+  if (HasNoDuplicateCall(BB)) return false;
+
   // Okay, this is a simple enough basic block.  See if any phi values are
   // constants.
   for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
diff --git a/test/Transforms/SimplifyCFG/attr-noduplicate.ll b/test/Transforms/SimplifyCFG/attr-noduplicate.ll
new file mode 100644
index 0000000..523aa51
--- /dev/null
+++ b/test/Transforms/SimplifyCFG/attr-noduplicate.ll
@@ -0,0 +1,37 @@
+; RUN: opt < %s -simplifycfg -S | FileCheck %s
+
+; This test checks that the SimplifyCFG pass won't duplicate a call to a
+; function marked noduplicate.
+;
+; CHECK-LABEL: @noduplicate
+; CHECK: call void @barrier
+; CHECK-NOT: call void @barrier
+define void @noduplicate(i32 %cond, i32* %out) {
+entry:
+  %out1 = getelementptr i32* %out, i32 1
+  %out2 = getelementptr i32* %out, i32 2
+  %cmp = icmp eq i32 %cond, 0
+  br i1 %cmp, label %if.then, label %if.end
+
+if.then:
+  store i32 5, i32* %out
+  br label %if.end
+
+if.end:
+  call void @barrier() #0
+  br i1 %cmp, label %cond.end, label %cond.false
+
+cond.false:
+  store i32 5, i32* %out1
+  br label %cond.end
+
+cond.end:
+  %value = phi i32 [ 1, %cond.false ], [ 0, %if.end ]
+  store i32 %value, i32* %out2
+  ret void
+}
+
+; Function Attrs: noduplicate nounwind
+declare void @barrier() #0
+
+attributes #0 = { noduplicate nounwind }
-- 
1.7.11.4