[llvm-branch-commits] [llvm] 8d75d90 - [DebugInfo] Don't use DW_OP_implicit_value for fragments
Pavel Labath via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Tue Dec 22 01:12:42 PST 2020
Author: Pavel Labath
Date: 2020-12-22T10:07:47+01:00
New Revision: 8d75d902a955602feb7e2501e34f814ff5630415
URL: https://github.com/llvm/llvm-project/commit/8d75d902a955602feb7e2501e34f814ff5630415
DIFF: https://github.com/llvm/llvm-project/commit/8d75d902a955602feb7e2501e34f814ff5630415.diff
LOG: [DebugInfo] Don't use DW_OP_implicit_value for fragments
Currently using DW_OP_implicit_value in fragments produces invalid DWARF
expressions. (Such a case can occur in complex floats, for example.)
This problem manifests itself as a missing DW_OP_piece operation after
the last fragment. This happens because the function for printing
constant float value skips printing the accompanying DWARF expression,
as that would also print DW_OP_stack_value (which is not desirable in
this case). However, this also results in DW_OP_piece being skipped.
The reason that DW_OP_piece is missing only for the last piece is that
the act of printing the next fragment corrects this. However, it does
that for the wrong reason -- the code emitting this DW_OP_piece thinks
that the previous fragment was missing, and so it thinks that it needs
to skip over it in order to be able to print itself.
In a simple scenario this works out, but it's likely that in a more
complex setup (where some pieces are in fact missing), this logic would
go badly wrong. In a simple setup gdb also seems to not mind the fact
that the DW_OP_piece is missing, but it would also likely not handle
more complex use cases.
For this reason, this patch disables the usage of DW_OP_implicit_value
in the frament scenario (we will use DW_OP_const*** instead), until we
figure out the right way to deal with this. This guarantees that we
produce valid expressions, and gdb can handle both kinds of inputs
anyway.
Differential Revision: https://reviews.llvm.org/D92013
Added:
Modified:
llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
llvm/test/DebugInfo/X86/implicit_value-double.ll
Removed:
################################################################################
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 75b4a2831b0f..6127c503404f 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -2477,13 +2477,13 @@ void DwarfDebug::emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
DwarfExpr.addExpression(std::move(ExprCursor));
return;
} else if (Value.isConstantFP()) {
- if (AP.getDwarfVersion() >= 4 && !AP.getDwarfDebug()->tuneForSCE()) {
+ if (AP.getDwarfVersion() >= 4 && !AP.getDwarfDebug()->tuneForSCE() &&
+ !ExprCursor) {
DwarfExpr.addConstantFP(Value.getConstantFP()->getValueAPF(), AP);
return;
- } else if (Value.getConstantFP()
- ->getValueAPF()
- .bitcastToAPInt()
- .getBitWidth() <= 64 /*bits*/)
+ }
+ if (Value.getConstantFP()->getValueAPF().bitcastToAPInt().getBitWidth() <=
+ 64 /*bits*/)
DwarfExpr.addUnsignedConstant(
Value.getConstantFP()->getValueAPF().bitcastToAPInt());
else
diff --git a/llvm/test/DebugInfo/X86/implicit_value-double.ll b/llvm/test/DebugInfo/X86/implicit_value-double.ll
index f205cb9a68ee..956c896b8d34 100644
--- a/llvm/test/DebugInfo/X86/implicit_value-double.ll
+++ b/llvm/test/DebugInfo/X86/implicit_value-double.ll
@@ -1,8 +1,8 @@
;; This test checks for emission of DW_OP_implicit_value operation
;; for double type.
-; RUN: llc -debugger-tune=gdb -filetype=obj %s -o - | llvm-dwarfdump - | FileCheck %s
-; RUN: llc -debugger-tune=lldb -filetype=obj %s -o - | llvm-dwarfdump - | FileCheck %s
+; RUN: llc -O0 -debugger-tune=gdb -filetype=obj %s -o - | llvm-dwarfdump - | FileCheck %s --check-prefixes=CHECK,BOTH
+; RUN: llc -O0 -debugger-tune=lldb -filetype=obj %s -o - | llvm-dwarfdump - | FileCheck %s --check-prefixes=CHECK,BOTH
; CHECK: .debug_info contents:
; CHECK: DW_TAG_variable
@@ -10,7 +10,7 @@
; CHECK-NEXT: [{{.*}}): DW_OP_implicit_value 0x8 0x1f 0x85 0xeb 0x51 0xb8 0x1e 0x09 0x40)
; CHECK-NEXT: DW_AT_name ("d")
-; RUN: llc -debugger-tune=sce -filetype=obj %s -o - | llvm-dwarfdump - | FileCheck %s -check-prefix=SCE-CHECK
+; RUN: llc -O0 -debugger-tune=sce -filetype=obj %s -o - | llvm-dwarfdump - | FileCheck %s -check-prefixes=SCE-CHECK,BOTH
; SCE-CHECK: .debug_info contents:
; SCE-CHECK: DW_TAG_variable
@@ -18,13 +18,11 @@
; SCE-CHECK-NEXT: [{{.*}}): DW_OP_constu 0x40091eb851eb851f, DW_OP_stack_value)
; SCE-CHECK-NEXT: DW_AT_name ("d")
-;; Generated from: clang -ggdb -O1
-;;int main() {
-;; double d = 3.14;
-;; printf("dummy\n");
-;; d *= d;
-;; return 0;
-;;}
+;; Using DW_OP_implicit_value for fragments is not currently supported.
+; BOTH: DW_TAG_variable
+; BOTH-NEXT: DW_AT_location ({{.*}}
+; BOTH-NEXT: [{{.*}}): DW_OP_constu 0x4047800000000000, DW_OP_stack_value, DW_OP_piece 0x8, DW_OP_constu 0x4052800000000000, DW_OP_stack_value, DW_OP_piece 0x8)
+; BOTH-NEXT: DW_AT_name ("c")
; ModuleID = 'implicit_value-double.c'
source_filename = "implicit_value-double.c"
@@ -37,6 +35,8 @@ target triple = "x86_64-unknown-linux-gnu"
define dso_local i32 @main() local_unnamed_addr #0 !dbg !7 {
entry:
call void @llvm.dbg.value(metadata double 3.140000e+00, metadata !12, metadata !DIExpression()), !dbg !14
+ call void @llvm.dbg.value(metadata double 4.700000e+01, metadata !17, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 64)), !dbg !14
+ call void @llvm.dbg.value(metadata double 7.400000e+01, metadata !17, metadata !DIExpression(DW_OP_LLVM_fragment, 64, 64)), !dbg !14
%puts = call i32 @puts(i8* nonnull dereferenceable(1) getelementptr inbounds ([6 x i8], [6 x i8]* @str, i64 0, i64 0)), !dbg !15
call void @llvm.dbg.value(metadata double undef, metadata !12, metadata !DIExpression()), !dbg !14
ret i32 0, !dbg !16
@@ -67,9 +67,11 @@ attributes #2 = { nofree nounwind }
!8 = !DISubroutineType(types: !9)
!9 = !{!10}
!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
-!11 = !{!12}
+!11 = !{!12, !17}
!12 = !DILocalVariable(name: "d", scope: !7, file: !1, line: 2, type: !13)
!13 = !DIBasicType(name: "double", size: 64, encoding: DW_ATE_float)
!14 = !DILocation(line: 0, scope: !7)
!15 = !DILocation(line: 3, column: 2, scope: !7)
!16 = !DILocation(line: 5, column: 2, scope: !7)
+!17 = !DILocalVariable(name: "c", scope: !7, file: !1, line: 2, type: !18)
+!18 = !DIBasicType(name: "complex", size: 128, encoding: DW_ATE_complex_float)
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