If converter was being too cute. It look for root BBs (which don't have

successors) and use inverse depth first search to traverse the BBs. However
that doesn't work when the CFG has infinite loops. Simply do a linear
traversal of all BBs work just fine.

rdar://9344645

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130324 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/IfConversion.cpp b/lib/CodeGen/IfConversion.cpp
index db53b0473a9a9dfbb1b52a0f2c1b2d1ba3d699ad..790200b8df5fc911d1368ca6ffa9e8723e26b2aa 100644 (file)
--- a/lib/CodeGen/IfConversion.cpp
+++ b/lib/CodeGen/IfConversion.cpp
@@ -27,7 +27,6 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
-#include "llvm/ADT/DepthFirstIterator.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/STLExtras.h"
@@ -146,10 +145,6 @@ namespace {
         : BBI(b), Kind(k), NeedSubsumption(s), NumDups(d), NumDups2(d2) {}
     };
 
-    /// Roots - Basic blocks that do not have successors. These are the starting
-    /// points of Graph traversal.
-    std::vector<MachineBasicBlock*> Roots;
-
     /// BBAnalysis - Results of if-conversion feasibility analysis indexed by
     /// basic block number.
     std::vector<BBInfo> BBAnalysis;
@@ -287,11 +282,6 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
   MF.RenumberBlocks();
   BBAnalysis.resize(MF.getNumBlockIDs());
 
-  // Look for root nodes, i.e. blocks without successors.
-  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
-    if (I->succ_empty())
-      Roots.push_back(I);
-
   std::vector<IfcvtToken*> Tokens;
   MadeChange = false;
   unsigned NumIfCvts = NumSimple + NumSimpleFalse + NumTriangle +
@@ -406,7 +396,6 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
   }
 
   Tokens.clear();
-  Roots.clear();
   BBAnalysis.clear();
 
   if (MadeChange && IfCvtBranchFold) {
@@ -924,13 +913,9 @@ IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
 /// candidates.
 void IfConverter::AnalyzeBlocks(MachineFunction &MF,
                                 std::vector<IfcvtToken*> &Tokens) {
-  std::set<MachineBasicBlock*> Visited;
-  for (unsigned i = 0, e = Roots.size(); i != e; ++i) {
-    for (idf_ext_iterator<MachineBasicBlock*> I=idf_ext_begin(Roots[i],Visited),
-           E = idf_ext_end(Roots[i], Visited); I != E; ++I) {
-      MachineBasicBlock *BB = *I;
-      AnalyzeBlock(BB, Tokens);
-    }
+  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
+    MachineBasicBlock *BB = I;
+    AnalyzeBlock(BB, Tokens);
   }
 
   // Sort to favor more complex ifcvt scheme.

diff --git a/test/CodeGen/ARM/2011-04-27-IfCvtBug.ll b/test/CodeGen/ARM/2011-04-27-IfCvtBug.ll
new file mode 100644 (file)
index 0000000..0741049
--- /dev/null
+++ b/test/CodeGen/ARM/2011-04-27-IfCvtBug.ll
@@ -0,0 +1,59 @@
+; RUN: llc < %s -mtriple=thumbv7-apple-ios
+
+; If converter was being too cute. It look for root BBs (which don't have
+; successors) and use inverse depth first search to traverse the BBs. However
+; that doesn't work when the CFG has infinite loops. Simply do a linear
+; traversal of all BBs work just fine.
+
+; rdar://9344645
+
+%struct.hc = type { i32, i32, i32, i32 }
+
+define i32 @t(i32 %type) optsize {
+entry:
+  br i1 undef, label %if.then, label %if.else
+
+if.then:
+  unreachable
+
+if.else:
+  br i1 undef, label %if.then15, label %if.else18
+
+if.then15:
+  unreachable
+
+if.else18:
+  switch i32 %type, label %if.else173 [
+    i32 3, label %if.then115
+    i32 1, label %if.then102
+  ]
+
+if.then102:
+  br i1 undef, label %cond.true10.i, label %t.exit
+
+cond.true10.i:
+  br label %t.exit
+
+t.exit:
+  unreachable
+
+if.then115:
+  br i1 undef, label %if.else163, label %if.else145
+
+if.else145:
+  %call150 = call fastcc %struct.hc* @foo(%struct.hc* undef, i32 34865152) optsize
+  br label %while.body172
+
+if.else163:
+  %call168 = call fastcc %struct.hc* @foo(%struct.hc* undef, i32 34078720) optsize
+  br label %while.body172
+
+while.body172:
+  br label %while.body172
+
+if.else173:
+  ret i32 -1
+}
+
+declare hidden fastcc %struct.hc* @foo(%struct.hc* nocapture, i32) nounwind optsize
+