From 66827427e1ef0e14399f24b6711e704ed96a3362 Mon Sep 17 00:00:00 2001
From: Rong Xu <xur@google.com>
Date: Wed, 16 Nov 2016 20:50:06 +0000
Subject: [PATCH] Make block placement deterministic

We fail to produce bit-to-bit matching stage2 and stage3 compiler in PGO
bootstrap build. The reason is because LoopBlockSet is of SmallPtrSet type
whose iterating order depends on the pointer value.

This patch fixes this issue by changing to use SmallSetVector.

Differential Revision: http://reviews.llvm.org/D26634

llvm-svn: 287148
---
 llvm/lib/CodeGen/MachineBlockPlacement.cpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/CodeGen/MachineBlockPlacement.cpp b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
index 2f43d2c06d51..32c0bcf310cd 100644
--- a/llvm/lib/CodeGen/MachineBlockPlacement.cpp
+++ b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
@@ -264,7 +264,7 @@ public:
 namespace {
 class MachineBlockPlacement : public MachineFunctionPass {
   /// \brief A typedef for a block filter set.
-  typedef SmallPtrSet<MachineBasicBlock *, 16> BlockFilterSet;
+  typedef SmallSetVector<MachineBasicBlock *, 16> BlockFilterSet;
 
   /// \brief work lists of blocks that are ready to be laid out
   SmallVector<MachineBasicBlock *, 16> BlockWorkList;
@@ -1512,7 +1512,7 @@ void MachineBlockPlacement::buildLoopChains(MachineLoop &L) {
     }
     for (MachineBasicBlock *ChainBB : LoopChain) {
       dbgs() << "          ... " << getBlockName(ChainBB) << "\n";
-      if (!LoopBlockSet.erase(ChainBB)) {
+      if (!LoopBlockSet.remove(ChainBB)) {
         // We don't mark the loop as bad here because there are real situations
         // where this can occur. For example, with an unanalyzable fallthrough
         // from a loop block to a non-loop block or vice versa.
@@ -1928,7 +1928,7 @@ bool MachineBlockPlacement::maybeTailDuplicateBlock(
 
         // Handle the filter set
         if (BlockFilter) {
-          BlockFilter->erase(RemBB);
+          BlockFilter->remove(RemBB);
         }
 
         // Remove the block from loop info.