DebugInfo: Don't lose unreferenced non-trivial by-value parameters

A FastISel optimization was causing us to emit no information for such
parameters & when they go missing we end up emitting a different
function type. By avoiding that shortcut we not only get types correct
(very important) but also location information (handy) - even if it's
only live at the start of a function & may be clobbered later.

Reviewed/discussion by Evan Cheng & Dan Gohman.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184604 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 4 insertions, 10 deletions

diff --git a/lib/CodeGen/SelectionDAG/FastISel.cpp b/lib/CodeGen/SelectionDAG/FastISel.cpp
index 82f9f76..49169b4 100644
--- a/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -97,14 +97,12 @@ bool FastISel::LowerArguments() {
   if (!FastLowerArguments())
     return false;
 
-  // Enter non-dead arguments into ValueMap for uses in non-entry BBs.
+  // Enter arguments into ValueMap for uses in non-entry BBs.
   for (Function::const_arg_iterator I = FuncInfo.Fn->arg_begin(),
          E = FuncInfo.Fn->arg_end(); I != E; ++I) {
-    if (!I->use_empty()) {
-      DenseMap<const Value *, unsigned>::iterator VI = LocalValueMap.find(I);
-      assert(VI != LocalValueMap.end() && "Missed an argument?");
-      FuncInfo.ValueMap[I] = VI->second;
-    }
+    DenseMap<const Value *, unsigned>::iterator VI = LocalValueMap.find(I);
+    assert(VI != LocalValueMap.end() && "Missed an argument?");
+    FuncInfo.ValueMap[I] = VI->second;
   }
   return true;
 }
diff --git a/lib/Target/ARM/ARMFastISel.cpp b/lib/Target/ARM/ARMFastISel.cpp
index 97dc63f..7f52749 100644
--- a/lib/Target/ARM/ARMFastISel.cpp
+++ b/lib/Target/ARM/ARMFastISel.cpp
@@ -3030,8 +3030,6 @@ bool ARMFastISel::FastLowerArguments() {
   Idx = 0;
   for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
        I != E; ++I, ++Idx) {
-    if (I->use_empty())
-      continue;
     unsigned SrcReg = GPRArgRegs[Idx];
     unsigned DstReg = FuncInfo.MF->addLiveIn(SrcReg, RC);
     // FIXME: Unfortunately it's necessary to emit a copy from the livein copy.
diff --git a/lib/Target/X86/X86FastISel.cpp b/lib/Target/X86/X86FastISel.cpp
index 295a577..669108f 100644
--- a/lib/Target/X86/X86FastISel.cpp
+++ b/lib/Target/X86/X86FastISel.cpp
@@ -1732,8 +1732,6 @@ bool X86FastISel::FastLowerArguments() {
   const TargetRegisterClass *RC64 = TLI.getRegClassFor(MVT::i64);
   for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
        I != E; ++I, ++Idx) {
-    if (I->use_empty())
-      continue;
     bool is32Bit = TLI.getValueType(I->getType()) == MVT::i32;
     const TargetRegisterClass *RC = is32Bit ? RC32 : RC64;
     unsigned SrcReg = is32Bit ? GPR32ArgRegs[Idx] : GPR64ArgRegs[Idx];