X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FCriticalAntiDepBreaker.cpp;h=2eb9f6034339ac517787d76ebe225c8ec3e32717;hb=af2fa71a64f66f38d6805ec3ab57bc3f41eefc57;hp=3e0f7404dd7796ee836a142c0f481af3724436da;hpb=0029534141ee83d827267d4ac9418bbed5704c2e;p=oota-llvm.git

diff --git a/lib/CodeGen/CriticalAntiDepBreaker.cpp b/lib/CodeGen/CriticalAntiDepBreaker.cpp
index 3e0f7404dd7..2eb9f603433 100644
--- a/lib/CodeGen/CriticalAntiDepBreaker.cpp
+++ b/lib/CodeGen/CriticalAntiDepBreaker.cpp
@@ -22,22 +22,19 @@
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
 
 using namespace llvm;
 
 #define DEBUG_TYPE "post-RA-sched"
 
-CriticalAntiDepBreaker::
-CriticalAntiDepBreaker(MachineFunction& MFi, const RegisterClassInfo &RCI) :
-  AntiDepBreaker(), MF(MFi),
-  MRI(MF.getRegInfo()),
-  TII(MF.getTarget().getInstrInfo()),
-  TRI(MF.getTarget().getRegisterInfo()),
-  RegClassInfo(RCI),
-  Classes(TRI->getNumRegs(), nullptr),
-  KillIndices(TRI->getNumRegs(), 0),
-  DefIndices(TRI->getNumRegs(), 0),
-  KeepRegs(TRI->getNumRegs(), false) {}
+CriticalAntiDepBreaker::CriticalAntiDepBreaker(MachineFunction &MFi,
+                                               const RegisterClassInfo &RCI)
+    : AntiDepBreaker(), MF(MFi), MRI(MF.getRegInfo()),
+      TII(MF.getSubtarget().getInstrInfo()),
+      TRI(MF.getSubtarget().getRegisterInfo()), RegClassInfo(RCI),
+      Classes(TRI->getNumRegs(), nullptr), KillIndices(TRI->getNumRegs(), 0),
+      DefIndices(TRI->getNumRegs(), 0), KeepRegs(TRI->getNumRegs(), false) {}
 
 CriticalAntiDepBreaker::~CriticalAntiDepBreaker() {
 }
@@ -200,6 +197,28 @@ void CriticalAntiDepBreaker::PrescanInstruction(MachineInstr *MI) {
     if (Classes[Reg] != reinterpret_cast<TargetRegisterClass *>(-1))
       RegRefs.insert(std::make_pair(Reg, &MO));
 
+    // If this reg is tied and live (Classes[Reg] is set to -1), we can't change
+    // it or any of its sub or super regs. We need to use KeepRegs to mark the
+    // reg because not all uses of the same reg within an instruction are
+    // necessarily tagged as tied.
+    // Example: an x86 "xor %eax, %eax" will have one source operand tied to the
+    // def register but not the second (see PR20020 for details).
+    // FIXME: can this check be relaxed to account for undef uses
+    // of a register? In the above 'xor' example, the uses of %eax are undef, so
+    // earlier instructions could still replace %eax even though the 'xor'
+    // itself can't be changed.
+    if (MI->isRegTiedToUseOperand(i) &&
+        Classes[Reg] == reinterpret_cast<TargetRegisterClass *>(-1)) {
+      for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
+           SubRegs.isValid(); ++SubRegs) {
+        KeepRegs.set(*SubRegs);
+      }
+      for (MCSuperRegIterator SuperRegs(Reg, TRI);
+           SuperRegs.isValid(); ++SuperRegs) {
+        KeepRegs.set(*SuperRegs);
+      }
+    }
+
     if (MO.isUse() && Special) {
       if (!KeepRegs.test(Reg)) {
         for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
@@ -236,20 +255,17 @@ void CriticalAntiDepBreaker::ScanInstruction(MachineInstr *MI,
       unsigned Reg = MO.getReg();
       if (Reg == 0) continue;
       if (!MO.isDef()) continue;
+
+      // If we've already marked this reg as unchangeable, carry on.
+      if (KeepRegs.test(Reg)) continue;
+      
       // Ignore two-addr defs.
       if (MI->isRegTiedToUseOperand(i)) continue;
 
-      DefIndices[Reg] = Count;
-      KillIndices[Reg] = ~0u;
-      assert(((KillIndices[Reg] == ~0u) !=
-              (DefIndices[Reg] == ~0u)) &&
-             "Kill and Def maps aren't consistent for Reg!");
-      KeepRegs.reset(Reg);
-      Classes[Reg] = nullptr;
-      RegRefs.erase(Reg);
-      // Repeat, for all subregs.
-      for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
-        unsigned SubregReg = *SubRegs;
+      // For the reg itself and all subregs: update the def to current;
+      // reset the kill state, any restrictions, and references.
+      for (MCSubRegIterator SRI(Reg, TRI, true); SRI.isValid(); ++SRI) {
+        unsigned SubregReg = *SRI;
         DefIndices[SubregReg] = Count;
         KillIndices[SubregReg] = ~0u;
         KeepRegs.reset(SubregReg);
@@ -282,15 +298,8 @@ void CriticalAntiDepBreaker::ScanInstruction(MachineInstr *MI,
     RegRefs.insert(std::make_pair(Reg, &MO));
 
     // It wasn't previously live but now it is, this is a kill.
-    if (KillIndices[Reg] == ~0u) {
-      KillIndices[Reg] = Count;
-      DefIndices[Reg] = ~0u;
-          assert(((KillIndices[Reg] == ~0u) !=
-                  (DefIndices[Reg] == ~0u)) &&
-               "Kill and Def maps aren't consistent for Reg!");
-    }
-    // Repeat, for all aliases.
-    for (MCRegAliasIterator AI(Reg, TRI, false); AI.isValid(); ++AI) {
+    // Repeat for all aliases.
+    for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) {
       unsigned AliasReg = *AI;
       if (KillIndices[AliasReg] == ~0u) {
         KillIndices[AliasReg] = Count;