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

3 files changed, 31 insertions, 14 deletions

diff --git a/include/llvm/CodeGen/LiveVariables.h b/include/llvm/CodeGen/LiveVariables.h
index 0d932cf198..bb050f2603 100644
--- a/include/llvm/CodeGen/LiveVariables.h
+++ b/include/llvm/CodeGen/LiveVariables.h
@@ -146,7 +146,7 @@ private:   // Intermediate data structures
   /// HandlePhysRegKill - Add kills of Reg and its sub-registers to the
   /// uses. Pay special attention to the sub-register uses which may come below
   /// the last use of the whole register.
-  bool HandlePhysRegKill(unsigned Reg);
+  bool HandlePhysRegKill(unsigned Reg, MachineInstr *MI);
 
   void HandlePhysRegUse(unsigned Reg, MachineInstr *MI);
   void HandlePhysRegDef(unsigned Reg, MachineInstr *MI);
diff --git a/lib/CodeGen/LiveVariables.cpp b/lib/CodeGen/LiveVariables.cpp
index ecfebc5511..a7bdbd92ff 100644
--- a/lib/CodeGen/LiveVariables.cpp
+++ b/lib/CodeGen/LiveVariables.cpp
@@ -335,7 +335,7 @@ bool LiveVariables::hasRegisterUseBelow(unsigned Reg,
   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 @@ bool LiveVariables::HandlePhysRegKill(unsigned Reg) {
       }
     }
   }
-  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 @@ void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI) {
 
   // 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 @@ void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI) {
           }
         } 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 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
       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.
diff --git a/test/CodeGen/X86/pr3243.ll b/test/CodeGen/X86/pr3243.ll
new file mode 100644
index 0000000000..7be887b38e
--- /dev/null
+++ b/test/CodeGen/X86/pr3243.ll
@@ -0,0 +1,15 @@
+; RUN: llvm-as < %s | llc -march=x86
+; PR3243
+
+declare signext i16 @safe_mul_func_int16_t_s_s(i16 signext, i32) nounwind readnone optsize
+
+define i32 @func_120(i32 %p_121) nounwind optsize {
+entry:
+	%0 = trunc i32 %p_121 to i16		; <i16> [#uses=1]
+	%1 = urem i16 %0, -15461		; <i16> [#uses=1]
+	%phitmp1 = trunc i16 %1 to i8		; <i8> [#uses=1]
+	%phitmp2 = urem i8 %phitmp1, -1		; <i8> [#uses=1]
+	%phitmp3 = zext i8 %phitmp2 to i16		; <i16> [#uses=1]
+	%2 = tail call signext i16 @safe_mul_func_int16_t_s_s(i16 signext %phitmp3, i32 1) nounwind		; <i16> [#uses=0]
+	unreachable
+}