Revert "[DebugInfo] Make describeLoadedValue() reg aware"

This reverts commit 3cd93a4efcdeabeb20cb7bec9fbddcb540d337a1.
I'll recommit with a well-formatted arcanist commit message.

1 files changed, 33 insertions, 26 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 89a0e350f8f..0aa4ae3958e 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -595,6 +595,7 @@ static void collectCallSiteParameters(const MachineInstr *CallMI,
               Implicit.push_back(FwdReg);
             else
               Explicit.push_back(FwdReg);
+            break;
           }
         }
       }
@@ -639,33 +640,39 @@ static void collectCallSiteParameters(const MachineInstr *CallMI,
     for (auto Reg : concat<unsigned>(ExplicitFwdRegDefs, ImplicitFwdRegDefs))
       ForwardedRegWorklist.erase(Reg);
 
-    for (auto ParamFwdReg : ExplicitFwdRegDefs) {
-      if (auto ParamValue = TII->describeLoadedValue(*I, ParamFwdReg)) {
-        if (ParamValue->first.isImm()) {
-          int64_t Val = ParamValue->first.getImm();
-          DbgValueLoc DbgLocVal(ParamValue->second, Val);
+    // The describeLoadedValue() hook currently does not have any information
+    // about which register it should describe in case of multiple defines, so
+    // for now we only handle instructions where a forwarded register is (at
+    // least partially) defined by the instruction's single explicit define.
+    if (I->getNumExplicitDefs() != 1 || ExplicitFwdRegDefs.empty())
+      continue;
+    unsigned ParamFwdReg = ExplicitFwdRegDefs[0];
+
+    if (auto ParamValue = TII->describeLoadedValue(*I)) {
+      if (ParamValue->first.isImm()) {
+        int64_t Val = ParamValue->first.getImm();
+        DbgValueLoc DbgLocVal(ParamValue->second, Val);
+        finishCallSiteParam(DbgLocVal, ParamFwdReg);
+      } else if (ParamValue->first.isReg()) {
+        Register RegLoc = ParamValue->first.getReg();
+       // TODO: For now, there is no use of describing the value loaded into the
+       //       register that is also the source registers (e.g. $r0 = add $r0, x).
+       if (ParamFwdReg == RegLoc)
+         continue;
+
+        unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
+        Register FP = TRI->getFrameRegister(*MF);
+        bool IsSPorFP = (RegLoc == SP) || (RegLoc == FP);
+        if (TRI->isCalleeSavedPhysReg(RegLoc, *MF) || IsSPorFP) {
+          DbgValueLoc DbgLocVal(ParamValue->second,
+                                MachineLocation(RegLoc,
+                                                /*IsIndirect=*/IsSPorFP));
           finishCallSiteParam(DbgLocVal, ParamFwdReg);
-        } else if (ParamValue->first.isReg()) {
-          Register RegLoc = ParamValue->first.getReg();
-          // TODO: For now, there is no use of describing the value loaded into the
-          //       register that is also the source registers (e.g. $r0 = add $r0, x).
-          if (ParamFwdReg == RegLoc)
-            continue;
-
-          unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
-          Register FP = TRI->getFrameRegister(*MF);
-          bool IsSPorFP = (RegLoc == SP) || (RegLoc == FP);
-          if (TRI->isCalleeSavedPhysReg(RegLoc, *MF) || IsSPorFP) {
-            DbgValueLoc DbgLocVal(ParamValue->second,
-                                  MachineLocation(RegLoc,
-                                                  /*IsIndirect=*/IsSPorFP));
-            finishCallSiteParam(DbgLocVal, ParamFwdReg);
-          // TODO: Add support for entry value plus an expression.
-          } else if (ShouldTryEmitEntryVals &&
-                     ParamValue->second->getNumElements() == 0) {
-            ForwardedRegWorklist.insert(RegLoc);
-            RegsForEntryValues[RegLoc] = ParamFwdReg;
-          }
+        // TODO: Add support for entry value plus an expression.
+        } else if (ShouldTryEmitEntryVals &&
+                   ParamValue->second->getNumElements() == 0) {
+          ForwardedRegWorklist.insert(RegLoc);
+          RegsForEntryValues[RegLoc] = ParamFwdReg;
         }
       }
     }