Improve virtual register handling when computing debug information

Summary: Some backends, like WebAssembly, use virtual registers instead of physical registers. This crashes the DbgValueHistoryCalculator pass, which assumes that all registers are physical. Instead, skip virtual registers when iterating aliases, and assume that they are clobbered.

Reviewers: dexonsmith, dschuff, aprantl

Subscribers: yurydelendik, llvm-commits, jfb, sunfish

Differential Revision: https://reviews.llvm.org/D22590

llvm-svn: 278371

1 files changed, 16 insertions, 7 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp b/llvm/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp
index adc536f1add..480fca1454f 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp
@@ -31,7 +31,7 @@ static unsigned isDescribedByReg(const MachineInstr &MI) {
   assert(MI.isDebugValue());
   assert(MI.getNumOperands() == 4);
   // If location of variable is described using a register (directly or
-  // indirecltly), this register is always a first operand.
+  // indirectly), this register is always a first operand.
   return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : 0;
 }
 
@@ -164,7 +164,9 @@ static void collectChangingRegs(const MachineFunction *MF,
       // Look for register defs and register masks. Register masks are
       // typically on calls and they clobber everything not in the mask.
       for (const MachineOperand &MO : MI.operands()) {
-        if (MO.isReg() && MO.isDef() && MO.getReg()) {
+        // Skip virtual registers since they are handled by the parent.
+        if (MO.isReg() && MO.isDef() && MO.getReg() &&
+            !TRI->isVirtualRegister(MO.getReg())) {
           for (MCRegAliasIterator AI(MO.getReg(), TRI, true); AI.isValid();
                ++AI)
             Regs.set(*AI);
@@ -192,12 +194,18 @@ void llvm::calculateDbgValueHistory(const MachineFunction *MF,
         // some variables.
         for (const MachineOperand &MO : MI.operands()) {
           if (MO.isReg() && MO.isDef() && MO.getReg()) {
+            // If this is a virtual register, only clobber it since it doesn't
+            // have aliases.
+            if (TRI->isVirtualRegister(MO.getReg()))
+              clobberRegisterUses(RegVars, MO.getReg(), Result, MI);
             // If this is a register def operand, it may end a debug value
             // range.
-            for (MCRegAliasIterator AI(MO.getReg(), TRI, true); AI.isValid();
-                 ++AI)
-              if (ChangingRegs.test(*AI))
-                clobberRegisterUses(RegVars, *AI, Result, MI);
+            else {
+              for (MCRegAliasIterator AI(MO.getReg(), TRI, true); AI.isValid();
+                   ++AI)
+                if (ChangingRegs.test(*AI))
+                  clobberRegisterUses(RegVars, *AI, Result, MI);
+            }
           } else if (MO.isRegMask()) {
             // If this is a register mask operand, clobber all debug values in
             // non-CSRs.
@@ -238,7 +246,8 @@ void llvm::calculateDbgValueHistory(const MachineFunction *MF,
     if (!MBB.empty() && &MBB != &MF->back()) {
       for (auto I = RegVars.begin(), E = RegVars.end(); I != E;) {
         auto CurElem = I++; // CurElem can be erased below.
-        if (ChangingRegs.test(CurElem->first))
+        if (TRI->isVirtualRegister(CurElem->first) ||
+            ChangingRegs.test(CurElem->first))
           clobberRegisterUses(RegVars, CurElem, Result, MBB.back());
       }
     }