commit a894ae130b6e69a367aa691eec7e96973a20e901
author Evan Cheng <evan.cheng@apple.com> Tue Jan 20 21:25:12 2009 +0000
committer Evan Cheng <evan.cheng@apple.com> Tue Jan 20 21:25:12 2009 +0000
tree bea608a84ccd26f40b52d9c017d2ab0b4f7f79f0
parent 9c70819da0cb4e418adfff4e6610317dd7209eda

Fix PR3243: a LiveVariables bug. When HandlePhysRegKill is checking whether the last reference is also the last def (i.e. dead def), it should also check if last reference is the current machine instruction being processed. This can happen when it is processing a physical register use and setting the current machine instruction as sub-register's last ref.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62617 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/LiveVariables.cpp

diff --git a/lib/CodeGen/LiveVariables.cpp b/lib/CodeGen/LiveVariables.cpp
index ecfebc5..a7bdbd9 100644
--- a/lib/CodeGen/LiveVariables.cpp
+++ b/lib/CodeGen/LiveVariables.cpp
@@ -335,7 +335,7 @@
   return true;
 }
 
-bool LiveVariables::HandlePhysRegKill(unsigned Reg) {
+bool LiveVariables::HandlePhysRegKill(unsigned Reg, MachineInstr *MI) {
   if (!PhysRegUse[Reg] && !PhysRegDef[Reg])
     return false;
 
@@ -373,8 +373,10 @@
       }
     }
   }
-  if (LastRefOrPartRef == PhysRegDef[Reg])
-    // Not used at all.
+
+  if (LastRefOrPartRef == PhysRegDef[Reg] && LastRefOrPartRef != MI)
+    // If the last reference is the last def, then it's not used at all.
+    // That is, unless we are currently processing the last reference itself.
     LastRefOrPartRef->addRegisterDead(Reg, TRI, true);
 
   /* Partial uses. Mark register def dead and add implicit def of
@@ -427,14 +429,14 @@
 
   // Start from the largest piece, find the last time any part of the register
   // is referenced.
-  if (!HandlePhysRegKill(Reg)) {
+  if (!HandlePhysRegKill(Reg, MI)) {
     // Only some of the sub-registers are used.
     for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
          unsigned SubReg = *SubRegs; ++SubRegs) {
       if (!Live.count(SubReg))
         // Skip if this sub-register isn't defined.
         continue;
-      if (HandlePhysRegKill(SubReg)) {
+      if (HandlePhysRegKill(SubReg, MI)) {
         Live.erase(SubReg);
         for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
           Live.erase(*SS);
@@ -475,7 +477,7 @@
           }
         } else {
           // Otherwise, the super register is killed.
-          if (HandlePhysRegKill(SuperReg)) {
+          if (HandlePhysRegKill(SuperReg, MI)) {
             PhysRegDef[SuperReg]  = NULL;
             PhysRegUse[SuperReg]  = NULL;
             for (const unsigned *SS = TRI->getSubRegisters(SuperReg); *SS; ++SS) {
@@ -558,13 +560,13 @@
       SmallVector<unsigned, 4> DefRegs;
       for (unsigned i = 0; i != NumOperandsToProcess; ++i) {
         const MachineOperand &MO = MI->getOperand(i);
-        if (MO.isReg() && MO.getReg()) {
-          unsigned MOReg = MO.getReg();
-          if (MO.isUse())
-            UseRegs.push_back(MOReg);
-          if (MO.isDef())
-            DefRegs.push_back(MOReg);
-        }
+        if (!MO.isReg() || MO.getReg() == 0)
+          continue;
+        unsigned MOReg = MO.getReg();
+        if (MO.isUse())
+          UseRegs.push_back(MOReg);
+        if (MO.isDef())
+          DefRegs.push_back(MOReg);
       }
 
       // Process all uses.