[X86DomainReassignment] Don't compare stack-allocated values by address

Summary:
The Closure allocated in the main loop is allocated on the stack. However,
later in the code its address is taken (and used for comparisons). This
obviously doesn't work. In fact, the Closure will get the same stack address
during every loop iteration, rendering the check that intended to identify
Closure conflicts entirely ineffective. Fix this bug by giving every Closure
a unique ID and using that for comparison. Alternatively, we could heap
allocate the closure object.

Fixes PR37396
Fixes JuliaLang/julia#27032

Reviewers: craig.topper, guyblank

Reviewed By: craig.topper

Subscribers: vchuravy, llvm-commits

Differential Revision: https://reviews.llvm.org/D46800

llvm-svn: 332682

1 files changed, 35 insertions, 6 deletions

diff --git a/llvm/lib/Target/X86/X86DomainReassignment.cpp b/llvm/lib/Target/X86/X86DomainReassignment.cpp
index 3883aabe10d..45635252249 100644
--- a/llvm/lib/Target/X86/X86DomainReassignment.cpp
+++ b/llvm/lib/Target/X86/X86DomainReassignment.cpp
@@ -26,6 +26,7 @@
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/Printable.h"
 #include <bitset>
 
 using namespace llvm;
@@ -291,8 +292,12 @@ private:
   /// Domains which this closure can legally be reassigned to.
   std::bitset<NumDomains> LegalDstDomains;
 
+  /// An ID to uniquely identify this closure, even when it gets
+  /// moved around
+  unsigned ID;
+
 public:
-  Closure(std::initializer_list<RegDomain> LegalDstDomainList) {
+  Closure(unsigned ID, std::initializer_list<RegDomain> LegalDstDomainList) : ID(ID) {
     for (RegDomain D : LegalDstDomainList)
       LegalDstDomains.set(D);
   }
@@ -328,6 +333,27 @@ public:
     return Instrs;
   }
 
+  LLVM_DUMP_METHOD void dump(const MachineRegisterInfo *MRI) const {
+    dbgs() << "Registers: ";
+    bool First = true;
+    for (unsigned Reg : Edges) {
+      if (!First)
+        dbgs() << ", ";
+      First = false;
+      dbgs() << printReg(Reg, MRI->getTargetRegisterInfo(), 0, MRI);
+    }
+    dbgs() << "\n" << "Instructions:";
+    for (MachineInstr *MI : Instrs) {
+      dbgs() << "\n  ";
+      MI->print(dbgs());
+    }
+    dbgs() << "\n";
+  }
+
+  unsigned getID() const {
+    return ID;
+  }
+
 };
 
 class X86DomainReassignment : public MachineFunctionPass {
@@ -339,7 +365,7 @@ class X86DomainReassignment : public MachineFunctionPass {
   DenseSet<unsigned> EnclosedEdges;
 
   /// All instructions that are included in some closure.
-  DenseMap<MachineInstr *, Closure *> EnclosedInstrs;
+  DenseMap<MachineInstr *, unsigned> EnclosedInstrs;
 
 public:
   static char ID;
@@ -416,14 +442,14 @@ void X86DomainReassignment::visitRegister(Closure &C, unsigned Reg,
 void X86DomainReassignment::encloseInstr(Closure &C, MachineInstr *MI) {
   auto I = EnclosedInstrs.find(MI);
   if (I != EnclosedInstrs.end()) {
-    if (I->second != &C)
+    if (I->second != C.getID())
       // Instruction already belongs to another closure, avoid conflicts between
       // closure and mark this closure as illegal.
       C.setAllIllegal();
     return;
   }
 
-  EnclosedInstrs[MI] = &C;
+  EnclosedInstrs[MI] = C.getID();
   C.addInstruction(MI);
 
   // Mark closure as illegal for reassignment to domains, if there is no
@@ -705,6 +731,7 @@ bool X86DomainReassignment::runOnMachineFunction(MachineFunction &MF) {
   std::vector<Closure> Closures;
 
   // Go over all virtual registers and calculate a closure.
+  unsigned ClosureID = 0;
   for (unsigned Idx = 0; Idx < MRI->getNumVirtRegs(); ++Idx) {
     unsigned Reg = TargetRegisterInfo::index2VirtReg(Idx);
 
@@ -717,7 +744,7 @@ bool X86DomainReassignment::runOnMachineFunction(MachineFunction &MF) {
       continue;
 
     // Calculate closure starting with Reg.
-    Closure C({MaskDomain});
+    Closure C(ClosureID++, {MaskDomain});
     buildClosure(C, Reg);
 
     // Collect all closures that can potentially be converted.
@@ -725,12 +752,14 @@ bool X86DomainReassignment::runOnMachineFunction(MachineFunction &MF) {
       Closures.push_back(std::move(C));
   }
 
-  for (Closure &C : Closures)
+  for (Closure &C : Closures) {
+    DEBUG(C.dump(MRI));
     if (isReassignmentProfitable(C, MaskDomain)) {
       reassign(C, MaskDomain);
       ++NumClosuresConverted;
       Changed = true;
     }
+  }
 
   DeleteContainerSeconds(Converters);