[DebugInfo] Stop changing labels for register-described parameter DBG…

…_VALUEs Summary: This is a follow-up to D57510. This patch stops DebugHandlerBase from changing the starting label for the first non-overlapping, register-described parameter DBG_VALUEs to the beginning of the function. That code did not consider what defined the registers, which could result in the ranges for the debug values starting before their defining instructions. We currently do not emit debug values for constant values directly at the start of the function, so this code is still useful for such values, but my intention is to remove the code from DebugHandlerBase completely when we get there. One reason for removing it is that the code violates the history map's ranges, which I think can make it quite confusing when troubleshooting. In D57510, PrologEpilogInserter was amended so that parameter DBG_VALUEs now are kept at the start of the entry block, even after emission of prologue code. That was done to reduce the degradation of debug completeness from this patch. PR40638 is another example, where the lexical-scope trimming that LDV does, in combination with scheduling, results in instructions after the prologue being left without locations. There might be other cases where the DBG_VALUEs are pushed further down, for which the DebugHandlerBase code may be helpful, but as it now quite often result in incorrect locations, even after the prologue, it seems better to remove that code, and try to work our way up with accurate locations. In the long run we should maybe not aim to provide accurate locations inside the prologue. Some single location descriptions, at least those referring to stack values, generate inaccurate values inside the epilogue, so we maybe should not aim to achieve accuracy for location lists. However, it seems that we now emit line number programs that can result in GDB and LLDB stopping inside the prologue when doing line number stepping into functions. See PR40188 for more information. A summary of some of the changed test cases is available in PR40188#c2. Reviewers: aprantl, dblaikie, rnk, jmorse Reviewed By: aprantl Subscribers: jdoerfert, jholewinski, jvesely, javed.absar, llvm-commits Tags: #debug-info, #llvm Differential Revision: https://reviews.llvm.org/D57511 llvm-svn: 353928
llvm · Feb 13, 2019 · 9dbeca3 · 9dbeca3
1 parent ab061d3
commit 9dbeca3
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Showing 12 changed files with 35 additions and 21 deletions.
diff --git a/llvm/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp b/llvm/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp
@@ -215,24 +215,36 @@ void DebugHandlerBase::beginFunction(const MachineFunction *MF) {
     if (Ranges.empty())
       continue;
 
-    // The first mention of a function argument gets the CurrentFnBegin
-    // label, so arguments are visible when breaking at function entry.
+    auto IsDescribedByReg = [](const MachineInstr *MI) {
+      return MI->getOperand(0).isReg() && MI->getOperand(0).getReg();
+    };
+
+    // The first mention of a function argument gets the CurrentFnBegin label,
+    // so arguments are visible when breaking at function entry.
+    //
+    // We do not change the label for values that are described by registers,
+    // as that could place them above their defining instructions. We should
+    // ideally not change the labels for constant debug values either, since
+    // doing that violates the ranges that are calculated in the history map.
+    // However, we currently do not emit debug values for constant arguments
+    // directly at the start of the function, so this code is still useful.
     const DILocalVariable *DIVar = Ranges.front().first->getDebugVariable();
     if (DIVar->isParameter() &&
         getDISubprogram(DIVar->getScope())->describes(&MF->getFunction())) {
-      LabelsBeforeInsn[Ranges.front().first] = Asm->getFunctionBegin();
+      if (!IsDescribedByReg(Ranges.front().first))
+        LabelsBeforeInsn[Ranges.front().first] = Asm->getFunctionBegin();
       if (Ranges.front().first->getDebugExpression()->isFragment()) {
         // Mark all non-overlapping initial fragments.
         for (auto I = Ranges.begin(); I != Ranges.end(); ++I) {
           const DIExpression *Fragment = I->first->getDebugExpression();
-          if (std::all_of(Ranges.begin(), I,
+          if (std::any_of(Ranges.begin(), I,
                           [&](DbgValueHistoryMap::InstrRange Pred) {
-                            return !Fragment->fragmentsOverlap(
+                            return Fragment->fragmentsOverlap(
                                 Pred.first->getDebugExpression());
                           }))
-            LabelsBeforeInsn[I->first] = Asm->getFunctionBegin();
-          else
             break;
+          if (!IsDescribedByReg(I->first))
+            LabelsBeforeInsn[I->first] = Asm->getFunctionBegin();
         }
       }
     }

diff --git a/llvm/test/CodeGen/AMDGPU/llvm.dbg.value.ll b/llvm/test/CodeGen/AMDGPU/llvm.dbg.value.ll
@@ -4,6 +4,7 @@
 ; GCN-LABEL: {{^}}test_debug_value:
 ; NOOPT: .loc	1 1 42 prologue_end     ; /tmp/test_debug_value.cl:1:42
 ; NOOPT-NEXT: s_load_dwordx2 s[4:5], s[4:5], 0x0
+; NOOPT-NEXT: .Ltmp
 ; NOOPT-NEXT: ;DEBUG_VALUE: test_debug_value:globalptr_arg <- $sgpr4_sgpr5
 
 ; GCN: flat_store_dword

diff --git a/llvm/test/DebugInfo/AArch64/asan-stack-vars.mir b/llvm/test/DebugInfo/AArch64/asan-stack-vars.mir
@@ -28,7 +28,7 @@
 # CHECK: "_cmd"
 # CHECK: DW_TAG_formal_parameter
 # CHECK-NEXT: DW_AT_location
-# CHECK-NEXT:   [0x{{0*}}, 0x{{.*}}):
+# CHECK-NEXT:   [0x{{.*}}, 0x{{.*}}):
 # CHECK-NOT:    DW_AT_
 # CHECK:        [0x{{.*}}, [[FN_END]]):
 # CHECK-NEXT: DW_AT_name {{.*}}"imageSize"

diff --git a/llvm/test/DebugInfo/ARM/partial-subreg.ll b/llvm/test/DebugInfo/ARM/partial-subreg.ll
@@ -9,6 +9,7 @@
 ; CHECK:   DW_AT_name {{.*}}"subscript.get"
 ; CHECK:  DW_TAG_formal_parameter
 ; CHECK-NEXT: DW_AT_location [DW_FORM_sec_offset]	({{.*}}
+; CHECK-NEXT:  [0x{{.*}}, 0x{{.*}}): DW_OP_regx D16, DW_OP_piece 0x8, DW_OP_regx D17, DW_OP_piece 0x4
 ; CHECK-NEXT:  [0x{{.*}}, 0x{{.*}}): DW_OP_regx D16, DW_OP_piece 0x8, DW_OP_regx D17, DW_OP_piece 0x4, DW_OP_regx D16, DW_OP_piece 0x8, DW_OP_regx D17, DW_OP_piece 0x4
 
 source_filename = "simd.ll"

diff --git a/llvm/test/DebugInfo/COFF/fp-stack.ll b/llvm/test/DebugInfo/COFF/fp-stack.ll
@@ -10,14 +10,14 @@ entry:
   ret double %sub
 }
 
-; ASM:         .cv_def_range    Lfunc_begin0 Lfunc_end0, "A\021\200\000\000\000"
+; ASM:         .cv_def_range    Ltmp1 Lfunc_end0, "A\021\200\000\000\000"
 ; OBJ:    DefRangeRegisterSym {
 ; OBJ:      Register: ST0 (0x80)
 ; OBJ:      MayHaveNoName: 0
 ; OBJ:      LocalVariableAddrRange {
-; OBJ:        OffsetStart: .text+0x0
+; OBJ:        OffsetStart: .text+0x6
 ; OBJ:        ISectStart: 0x0
-; OBJ:        Range: 0x7
+; OBJ:        Range: 0x1
 ; OBJ:      }
 ; OBJ:    }
 

diff --git a/llvm/test/DebugInfo/COFF/fpo-stack-protect.ll b/llvm/test/DebugInfo/COFF/fpo-stack-protect.ll
@@ -30,7 +30,7 @@
 ; CHECK:         addl    $20, %esp
 ; CHECK:         popl    %esi
 ; CHECK:         retl
-; CHECK: Ltmp2:
+; CHECK: Ltmp3:
 ; CHECK:         .cv_fpo_endproc
 
 ; ModuleID = 't.c'

diff --git a/llvm/test/DebugInfo/COFF/pieces.ll b/llvm/test/DebugInfo/COFF/pieces.ll
@@ -136,7 +136,7 @@
 ; ASM:        .asciz  "pad_right"             # Function name
 ; ASM:        .short  4414                    # Record kind: S_LOCAL
 ; ASM:        .asciz  "o"
-; ASM:        .cv_def_range    .Lfunc_begin1 .Ltmp8, "C\021\021\000\000\000\004\000\000\000"
+; ASM:        .cv_def_range    .Ltmp8 .Ltmp8, "C\021\021\000\000\000\004\000\000\000"
 
 ; OBJ-LABEL: GlobalProcIdSym {
 ; OBJ:         Kind: S_GPROC32_ID (0x1147)
@@ -159,7 +159,7 @@
 ; ASM:        .asciz  "pad_left"              # Function name
 ; ASM:        .short  4414                    # Record kind: S_LOCAL
 ; ASM:        .asciz  "o"
-; ASM:        .cv_def_range    .Lfunc_begin2 .Ltmp10, "C\021\021\000\000\000\000\000\000\000"
+; ASM:        .cv_def_range    .Ltmp10 .Ltmp10, "C\021\021\000\000\000\000\000\000\000"
 
 ; OBJ-LABEL: GlobalProcIdSym {
 ; OBJ:         Kind: S_GPROC32_ID (0x1147)

diff --git a/llvm/test/DebugInfo/MIR/AArch64/clobber-sp.mir b/llvm/test/DebugInfo/MIR/AArch64/clobber-sp.mir
@@ -4,7 +4,7 @@
 # CHECK: DW_TAG_formal_parameter
 # CHECK: DW_TAG_formal_parameter
 # CHECK-NEXT: DW_AT_location
-# CHECK-NEXT:   [0x0000000000000000, 0x0000000000000014): DW_OP_reg1 W1
+# CHECK-NEXT:   [0x0000000000000010, 0x0000000000000014): DW_OP_reg1 W1
 # CHECK-NEXT:   [0x0000000000000014, 0x0000000000000038): DW_OP_breg31 WSP+8
 # CHECK-NEXT: DW_AT_name {{.*}}"y"
 

diff --git a/llvm/test/DebugInfo/NVPTX/debug-info.ll b/llvm/test/DebugInfo/NVPTX/debug-info.ll
@@ -4781,8 +4781,8 @@ if.end:                                           ; preds = %if.then, %entry
 ; CHECK-NEXT: .b8 6                                // DW_AT_call_line
 ; CHECK-NEXT: .b8 43                               // Abbrev [43] 0x270e:0x22 DW_TAG_inlined_subroutine
 ; CHECK-NEXT: .b32 9791                            // DW_AT_abstract_origin
-; CHECK-NEXT: .b64 Ltmp9                           // DW_AT_low_pc
-; CHECK-NEXT: .b64 Ltmp10                          // DW_AT_high_pc
+; CHECK-NEXT: .b64 Ltmp10                          // DW_AT_low_pc
+; CHECK-NEXT: .b64 Ltmp11                          // DW_AT_high_pc
 ; CHECK-NEXT: .b8 12                               // DW_AT_call_file
 ; CHECK-NEXT: .b8 8                                // DW_AT_call_line
 ; CHECK-NEXT: .b8 44                               // Abbrev [44] 0x2725:0x5 DW_TAG_formal_parameter

diff --git a/llvm/test/DebugInfo/X86/debug-loc-asan.mir b/llvm/test/DebugInfo/X86/debug-loc-asan.mir
@@ -27,7 +27,7 @@
 # We expect two location ranges for the variable.
 #
 # First, its address is stored in %rcx:
-# CHECK:      .quad .Lfunc_begin0-.Lfunc_begin0
+# CHECK:      .quad .Ltmp0-.Lfunc_begin0
 # CHECK-NEXT: .quad [[START_LABEL]]-.Lfunc_begin0
 # CHECK: DW_OP_breg2
 # DWARF:       DW_TAG_formal_parameter

diff --git a/llvm/test/DebugInfo/X86/debug-loc-offset.mir b/llvm/test/DebugInfo/X86/debug-loc-offset.mir
@@ -42,7 +42,7 @@
 # CHECK: DW_TAG_formal_parameter
 # CHECK-NOT: DW_TAG
 # CHECK:       DW_AT_location [DW_FORM_sec_offset]   ({{.*}}
-# CHECK-NEXT:    [0x00000020, 0x00000037): DW_OP_breg0 EAX+0, DW_OP_deref
+# CHECK-NEXT:    [0x00000029, 0x00000037): DW_OP_breg0 EAX+0, DW_OP_deref
 # CHECK-NEXT:    [0x00000037, 0x00000063): DW_OP_breg5 EBP-8, DW_OP_deref, DW_OP_deref
 # CHECK-NEXT:  DW_AT_name [DW_FORM_strp]{{.*}}"a"
 #
@@ -70,7 +70,7 @@
 # CHECK-NEXT:    [0x00000000, 0x0000000a): DW_OP_consts +0, DW_OP_stack_value
 # CHECK-NEXT:    [0x0000000a, 0x00000017): DW_OP_consts +1, DW_OP_stack_value
 # CHECK:       0x00000022:
-# CHECK-NEXT:    [0x00000000, 0x00000017): DW_OP_breg0 EAX+0, DW_OP_deref
+# CHECK-NEXT:    [0x00000009, 0x00000017): DW_OP_breg0 EAX+0, DW_OP_deref
 # CHECK-NEXT:    [0x00000017, 0x00000043): DW_OP_breg5 EBP-8, DW_OP_deref, DW_OP_deref
 --- |
   target triple = "i386-unknown-linux-gnu"

diff --git a/llvm/test/DebugInfo/X86/dw_op_minus_direct.ll b/llvm/test/DebugInfo/X86/dw_op_minus_direct.ll
@@ -17,7 +17,7 @@
 
 ; CHECK: .debug_loc contents:
 ; CHECK: 0x00000000:
-; CHECK-NEXT:   [0x0000000000000000, 0x0000000000000004): DW_OP_breg0 RAX+0, DW_OP_constu 0xffffffff, DW_OP_and, DW_OP_lit1, DW_OP_minus, DW_OP_stack_value
+; CHECK-NEXT:   [0x0000000000000003, 0x0000000000000004): DW_OP_breg0 RAX+0, DW_OP_constu 0xffffffff, DW_OP_and, DW_OP_lit1, DW_OP_minus, DW_OP_stack_value
 ;        rax+0, constu 0xffffffff, and, constu 0x00000001, minus, stack-value
 
 source_filename = "minus.c"