[DEBUG_INFO][NVPTX]Fix processing of DBG_VALUES.

Summary:
If the instruction in the eliminateFrameIndex function is a DBG_VALUE
instruction, it requires special processing. The frame register is set
to VRFrame and the offset is based on the object offset.
The code is similar to the code used in
lib/CodeGen/PrologEpilogInserter.cpp.

Reviewers: tra

Subscribers: jholewinski, llvm-commits

Differential Revision: https://reviews.llvm.org/D53657

llvm-svn: 345269

llvm/lib/Target/NVPTX/NVPTXPrologEpilogPass.cpp

@@ -20,6 +20,7 @@
 #include "llvm/CodeGen/TargetFrameLowering.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/CodeGen/TargetSubtargetInfo.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
@@ -60,6 +61,24 @@ bool NVPTXPrologEpilogPass::runOnMachineFunction(MachineFunction &MF) {
       for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
         if (!MI.getOperand(i).isFI())
           continue;
+
+        // Frame indices in debug values are encoded in a target independent
+        // way with simply the frame index and offset rather than any
+        // target-specific addressing mode.
+        if (MI.isDebugValue()) {
+          assert(i == 0 && "Frame indices can only appear as the first "
+                           "operand of a DBG_VALUE machine instruction");
+          unsigned Reg;
+          int64_t Offset =
+              TFI.getFrameIndexReference(MF, MI.getOperand(0).getIndex(), Reg);
+          MI.getOperand(0).ChangeToRegister(Reg, /*isDef=*/false);
+          MI.getOperand(0).setIsDebug();
+          auto *DIExpr = DIExpression::prepend(MI.getDebugExpression(),
+                                               DIExpression::NoDeref, Offset);
+          MI.getOperand(3).setMetadata(DIExpr);
+          continue;
+        }
+
         TRI.eliminateFrameIndex(MI, 0, i, nullptr);
         Modified = true;
       }

llvm/test/DebugInfo/NVPTX/dbg-value-const-byref.ll

@@ -0,0 +1,81 @@
+; RUN: llc -mtriple=nvptx64-nvidia-cuda < %s | FileCheck %s
+; Generated with -O1 from:
+; int f1();
+; void f2(int*);
+; int f3(int);
+;
+; int foo() {
+;   int i = 3;
+;   f3(i);
+;   i = 7;
+;   i = f1();
+;   f2(&i);
+;   return 0;
+; }
+;
+; Test that we generate valid debug info for optimized code,
+; particularly variables that are described as constants and passed
+; by reference.
+;
+; CHECK: DEBUG_VALUE: foo:i <- [DW_OP_deref] $vrdepot
+; CHECK: DEBUG_VALUE: foo:i <- 3
+; CHECK: DEBUG_VALUE: foo:i <- 7
+; CHECK: DEBUG_VALUE: foo:i <- %
+
+; Function Attrs: nounwind ssp uwtable
+define i32 @foo() #0 !dbg !4 {
+entry:
+  %i = alloca i32, align 4
+  call void @llvm.dbg.value(metadata i32 3, metadata !10, metadata !DIExpression()), !dbg !15
+  %call = call i32 @f3(i32 3) #3, !dbg !16
+  call void @llvm.dbg.value(metadata i32 7, metadata !10, metadata !DIExpression()), !dbg !18
+  %call1 = call i32 (...) @f1() #3, !dbg !19
+  call void @llvm.dbg.value(metadata i32 %call1, metadata !10, metadata !DIExpression()), !dbg !19
+  store i32 %call1, i32* %i, align 4, !dbg !19, !tbaa !20
+  call void @llvm.dbg.value(metadata i32* %i, metadata !10, metadata !DIExpression(DW_OP_deref)), !dbg !24
+  call void @f2(i32* %i) #3, !dbg !24
+  ret i32 0, !dbg !25
+}
+
+declare i32 @f3(i32)
+
+declare i32 @f1(...)
+
+declare void @f2(i32*)
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, metadata, metadata) #2
+
+attributes #0 = { nounwind ssp uwtable }
+attributes #2 = { nounwind readnone }
+attributes #3 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!11, !12}
+!llvm.ident = !{!13}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang version 3.5.0 ", isOptimized: true, emissionKind: FullDebug, file: !1, enums: !2, retainedTypes: !2, globals: !2, imports: !2)
+!1 = !DIFile(filename: "dbg-value-const-byref.c", directory: "")
+!2 = !{}
+!4 = distinct !DISubprogram(name: "foo", line: 5, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: true, unit: !0, scopeLine: 5, file: !1, scope: !5, type: !6, retainedNodes: !9)
+!5 = !DIFile(filename: "dbg-value-const-byref.c", directory: "")
+!6 = !DISubroutineType(types: !7)
+!7 = !{!8}
+!8 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!9 = !{!10}
+!10 = !DILocalVariable(name: "i", line: 6, scope: !4, file: !5, type: !8)
+!11 = !{i32 2, !"Dwarf Version", i32 2}
+!12 = !{i32 1, !"Debug Info Version", i32 3}
+!13 = !{!"clang version 3.5.0 "}
+!14 = !{i32 3}
+!15 = !DILocation(line: 6, scope: !4)
+!16 = !DILocation(line: 7, scope: !4)
+!17 = !{i32 7}
+!18 = !DILocation(line: 8, scope: !4)
+!19 = !DILocation(line: 9, scope: !4)
+!20 = !{!21, !21, i64 0}
+!21 = !{!"int", !22, i64 0}
+!22 = !{!"omnipotent char", !23, i64 0}
+!23 = !{!"Simple C/C++ TBAA"}
+!24 = !DILocation(line: 10, scope: !4)
+!25 = !DILocation(line: 11, scope: !4)