Correctly compute live variable information for physical registers

when an implicitely defined register is later used by an alias. For example:

         call foo
         %reg1024 = mov %AL

The call implicitely defines EAX but only AL is used. Before this fix
no information was available on AL. Now EAX and all its aliases except
AL get defined and die at the call instruction whereas AL lives to be
killed by the assignment.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10813 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 3 deletions

diff --git a/lib/CodeGen/RegAllocLocal.cpp b/lib/CodeGen/RegAllocLocal.cpp
index 88699d0bcb..5ffe5afc4d 100644
--- a/lib/CodeGen/RegAllocLocal.cpp
+++ b/lib/CodeGen/RegAllocLocal.cpp
@@ -232,9 +232,8 @@ void RA::removePhysReg(unsigned PhysReg) {
 
   std::vector<unsigned>::iterator It =
     std::find(PhysRegsUseOrder.begin(), PhysRegsUseOrder.end(), PhysReg);
-  assert(It != PhysRegsUseOrder.end() &&
-         "Spilled a physical register, but it was not in use list!");
-  PhysRegsUseOrder.erase(It);
+  if (It != PhysRegsUseOrder.end())
+    PhysRegsUseOrder.erase(It);
 }
 
 
@@ -550,6 +549,11 @@ void RA::AllocateBasicBlock(MachineBasicBlock &MBB) {
         spillPhysReg(MBB, I, Reg, true);  // Spill any existing value in the reg
         PhysRegsUsed[Reg] = 0;            // It is free and reserved now
         PhysRegsUseOrder.push_back(Reg);
+        for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
+             *AliasSet; ++AliasSet) {
+            PhysRegsUseOrder.push_back(*AliasSet);
+            PhysRegsUsed[*AliasSet] = 0;  // It is free and reserved now
+        }
       }
 
     // Loop over the implicit defs, spilling them as well.
@@ -559,6 +563,11 @@ void RA::AllocateBasicBlock(MachineBasicBlock &MBB) {
       spillPhysReg(MBB, I, Reg);
       PhysRegsUseOrder.push_back(Reg);
       PhysRegsUsed[Reg] = 0;            // It is free and reserved now
+      for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
+           *AliasSet; ++AliasSet) {
+          PhysRegsUseOrder.push_back(*AliasSet);
+          PhysRegsUsed[*AliasSet] = 0;  // It is free and reserved now
+      }
     }
 
     // Okay, we have allocated all of the source operands and spilled any values