vsk created this revision.
vsk added reviewers: aprantl, djtodoro, dblaikie.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.
Currently, clang emits subprograms for declared functions when the
target debugger or DWARF standard is known to support entry values
(DW_OP_entry_value & the GNU equivalent).
Treat DW_AT_tail_call the same way to allow debuggers to follow cross-TU
tail calls.
Pre-patch debug session with a cross-TU tail call:
* frame #0: 0x0000000100000fa4 main`target at b.c:4:3 [opt]
frame #1: 0x0000000100000f99 main`main at a.c:8:10 [opt]
Post-patch (note that the tail-calling frame, "helper", is visible):
* frame #0: 0x0000000100000fa4 main`target at b.c:4:3 [opt]
frame #1: 0x0000000100000f80 main`helper [opt] [artificial]
frame #2: 0x0000000100000f99 main`main at a.c:8:10 [opt]
This was reverted in 5b9a072c
<https://reviews.llvm.org/rG5b9a072c39c0c34a290abd19e4aca8208a9afae6> because
it attached declaration
subprograms to inlinable builtin calls, which interacted badly with the
MergeICmps pass. The fix is to not attach declarations to builtins.
rdar://46577651
Previous review: https://reviews.llvm.org/D69743
https://reviews.llvm.org/D69970
Files:
clang/lib/CodeGen/CGDebugInfo.cpp
clang/test/CodeGen/debug-info-extern-call.c
clang/test/CodeGenCXX/dbg-info-all-calls-described.cpp
llvm/test/DebugInfo/X86/dwarf-callsite-related-attrs.ll
Index: llvm/test/DebugInfo/X86/dwarf-callsite-related-attrs.ll
===================================================================
--- llvm/test/DebugInfo/X86/dwarf-callsite-related-attrs.ll
+++ llvm/test/DebugInfo/X86/dwarf-callsite-related-attrs.ll
@@ -25,6 +25,14 @@
@sink = global i32 0, align 4, !dbg !0
+define void @__has_no_subprogram() {
+entry:
+ %0 = load volatile i32, i32* @sink, align 4
+ %inc = add nsw i32 %0, 1
+ store volatile i32 %inc, i32* @sink, align 4
+ ret void
+}
+
; ASM: DW_TAG_subprogram
; ASM: DW_AT_call_all_calls
; OBJ: [[bat_sp:.*]]: DW_TAG_subprogram
@@ -70,6 +78,7 @@
; OBJ: DW_AT_call_tail_call
define void @_Z3foov() !dbg !25 {
entry:
+ tail call void @__has_no_subprogram()
tail call void @_Z3barv(), !dbg !26
tail call void @_Z3batv(), !dbg !27
tail call void @_Z3barv(), !dbg !26
Index: clang/test/CodeGenCXX/dbg-info-all-calls-described.cpp
===================================================================
--- clang/test/CodeGenCXX/dbg-info-all-calls-described.cpp
+++ clang/test/CodeGenCXX/dbg-info-all-calls-described.cpp
@@ -56,6 +56,7 @@
// NO-ATTR-NOT: FlagAllCallsDescribed
+// HAS-ATTR-DAG: DISubprogram(name: "declaration1", {{.*}}, flags: DIFlagPrototyped
// HAS-ATTR-DAG: DISubprogram(name: "declaration2", {{.*}}, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition
// HAS-ATTR-DAG: DISubprogram(name: "struct1", {{.*}}, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized)
// HAS-ATTR-DAG: DISubprogram(name: "struct1", {{.*}}, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition
Index: clang/test/CodeGen/debug-info-extern-call.c
===================================================================
--- clang/test/CodeGen/debug-info-extern-call.c
+++ clang/test/CodeGen/debug-info-extern-call.c
@@ -1,15 +1,32 @@
-// RUN: %clang -Xclang -femit-debug-entry-values -g -O2 -target x86_64-none-linux-gnu -S -emit-llvm %s -o - | FileCheck %s -check-prefix=CHECK-EXT
-// CHECK-EXT: !DISubprogram(name: "fn1"
+// When entry values are emitted, expect a subprogram for extern decls so that
+// the dwarf generator can describe call site parameters at extern call sites.
+//
+// RUN: %clang -Xclang -femit-debug-entry-values -g -O2 -target x86_64-none-linux-gnu -S -emit-llvm %s -o - \
+// RUN: | FileCheck %s -check-prefix=ENTRY-VAL -implicit-check-not='DISubprogram(name: "memcmp"'
+// ENTRY-VAL: !DISubprogram(name: "fn1"
-// RUN: %clang -g -O2 -target x86_64-none-linux-gnu -S -emit-llvm %s -o - | FileCheck %s
-// CHECK-NOT: !DISubprogram(name: "fn1"
+// Similarly, when the debugger tuning is gdb, expect a subprogram for extern
+// decls so that the dwarf generator can describe information needed for tail
+// call frame reconstrution.
+//
+// RUN: %clang -g -O2 -target x86_64-none-linux-gnu -ggdb -S -emit-llvm %s -o - \
+// RUN: | FileCheck %s -check-prefix=GDB -implicit-check-not='DISubprogram(name: "memcmp"'
+// GDB: !DISubprogram(name: "fn1"
+//
+// Do not emit a subprogram for extern decls when entry values are disabled and
+// the tuning is not set to gdb.
+//
+// RUN: %clang -g -O2 -target x86_64-none-linux-gnu -gsce -S -emit-llvm %s -o - \
+// RUN: | FileCheck %s -check-prefix=SCE -implicit-check-not='DISubprogram(name: "memcmp"'
+// SCE-NOT: !DISubprogram(name: "fn1"
extern int fn1(int a, int b);
+extern int memcmp(const void *s1, const void *s2, unsigned long n);
-int fn2 () {
+int fn2 (int *src, int *dst) {
int x = 4, y = 5;
int res = fn1(x, y);
-
- return res;
+ int res2 = memcmp(dst, src, res);
+ return res + res2;
}
Index: clang/lib/CodeGen/CGDebugInfo.cpp
===================================================================
--- clang/lib/CodeGen/CGDebugInfo.cpp
+++ clang/lib/CodeGen/CGDebugInfo.cpp
@@ -3748,9 +3748,10 @@
void CGDebugInfo::EmitFuncDeclForCallSite(llvm::CallBase *CallOrInvoke,
QualType CalleeType,
const FunctionDecl *CalleeDecl) {
- auto &CGOpts = CGM.getCodeGenOpts();
- if (!CGOpts.EnableDebugEntryValues || !CGM.getLangOpts().Optimize ||
- !CallOrInvoke)
+ // Do not emit a declaration subprogram for a builtin, or if call site info
+ // isn't required.
+ if (!CallOrInvoke || CalleeDecl->getBuiltinID() != 0 ||
+ getCallSiteRelatedAttrs() == llvm::DINode::FlagZero)
return;
auto *Func = CallOrInvoke->getCalledFunction();
@@ -4824,10 +4825,10 @@
bool SupportsDWARFv4Ext =
CGM.getCodeGenOpts().DwarfVersion == 4 &&
(CGM.getCodeGenOpts().getDebuggerTuning() == llvm::DebuggerKind::LLDB ||
- (CGM.getCodeGenOpts().EnableDebugEntryValues &&
- CGM.getCodeGenOpts().getDebuggerTuning() == llvm::DebuggerKind::GDB));
+ CGM.getCodeGenOpts().getDebuggerTuning() == llvm::DebuggerKind::GDB);
- if (!SupportsDWARFv4Ext && CGM.getCodeGenOpts().DwarfVersion < 5)
+ if (!SupportsDWARFv4Ext && CGM.getCodeGenOpts().DwarfVersion < 5 &&
+ !CGM.getCodeGenOpts().EnableDebugEntryValues)
return llvm::DINode::FlagZero;
return llvm::DINode::FlagAllCallsDescribed;
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