Patch to fix PR337. Make sure to mark all aliased physical registers as used

when we see a read of a register.  This is important in cases like:

AL = ...
AH = ...

   = AX

The read of AX must make both the AL and AH defs live until the use.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@13444 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 3 deletions

diff --git a/lib/CodeGen/LiveVariables.cpp b/lib/CodeGen/LiveVariables.cpp
index 759a0b3412..f1a7d9eb0f 100644
--- a/lib/CodeGen/LiveVariables.cpp
+++ b/lib/CodeGen/LiveVariables.cpp
@@ -126,6 +126,12 @@ void LiveVariables::HandleVirtRegUse(VarInfo &VRInfo, MachineBasicBlock *MBB,
 void LiveVariables::HandlePhysRegUse(unsigned Reg, MachineInstr *MI) {
   PhysRegInfo[Reg] = MI;
   PhysRegUsed[Reg] = true;
+
+  for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
+       unsigned Alias = *AliasSet; ++AliasSet) {
+    PhysRegInfo[Alias] = MI;
+    PhysRegUsed[Alias] = true;
+  }
 }
 
 void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI) {
@@ -140,11 +146,10 @@ void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI) {
   PhysRegUsed[Reg] = false;
 
   for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
-       *AliasSet; ++AliasSet) {
-    unsigned Alias = *AliasSet;
+       unsigned Alias = *AliasSet; ++AliasSet) {
     if (MachineInstr *LastUse = PhysRegInfo[Alias]) {
       if (PhysRegUsed[Alias])
-	RegistersKilled.insert(std::make_pair(LastUse, Alias));
+        RegistersKilled.insert(std::make_pair(LastUse, Alias));
       else
 	RegistersDead.insert(std::make_pair(LastUse, Alias));
     }