[llvm] 340b0ca - [llvm] Add DW_CC_nocall to function debug metadata when either return values or arguments are removed
Venkata Ramanaiah Nalamothu via llvm-commits
llvm-commits at lists.llvm.org
Tue Jun 14 15:00:22 PDT 2022
Author: Venkata Ramanaiah Nalamothu
Date: 2022-06-15T03:30:15+05:30
New Revision: 340b0ca90095d838f095271aaa1098fa1bd5ecbe
URL: https://github.com/llvm/llvm-project/commit/340b0ca90095d838f095271aaa1098fa1bd5ecbe
DIFF: https://github.com/llvm/llvm-project/commit/340b0ca90095d838f095271aaa1098fa1bd5ecbe.diff
LOG: [llvm] Add DW_CC_nocall to function debug metadata when either return values or arguments are removed
Adding the `DW_CC_nocall` calling convention to the function debug metadata is needed when either the return values or the arguments of a function are removed as this helps in informing debugger that it may not be safe to call this function or try to interpret the return value.
This translates to setting `DW_AT_calling_convention` with `DW_CC_nocall` for appropriate DWARF DIEs.
The DWARF5 spec (section 3.3.1.1 Calling Convention Information) says:
If the `DW_AT_calling_convention` attribute is not present, or its value is the constant `DW_CC_normal`, then the subroutine may be safely called by obeying the `standard` calling conventions of the target architecture. If the value of the calling convention attribute is the constant `DW_CC_nocall`, the subroutine does not obey standard calling conventions, and it may not be safe for the debugger to call this subroutine.
Reviewed By: dblaikie
Differential Revision: https://reviews.llvm.org/D127134
Added:
Modified:
llvm/include/llvm/IR/DebugInfoMetadata.h
llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
llvm/test/Transforms/DeadArgElim/2010-04-30-DbgInfo.ll
Removed:
################################################################################
diff --git a/llvm/include/llvm/IR/DebugInfoMetadata.h b/llvm/include/llvm/IR/DebugInfoMetadata.h
index bc916fe677b1c..0eb96d2343a0c 100644
--- a/llvm/include/llvm/IR/DebugInfoMetadata.h
+++ b/llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -1298,6 +1298,12 @@ class DISubroutineType : public DIType {
(Flags, CC, TypeArray))
TempDISubroutineType clone() const { return cloneImpl(); }
+ // Returns a new temporary DISubroutineType with updated CC
+ TempDISubroutineType cloneWithCC(uint8_t CC) const {
+ auto NewTy = clone();
+ NewTy->CC = CC;
+ return NewTy;
+ }
uint8_t getCC() const { return CC; }
@@ -1996,6 +2002,10 @@ class DISubprogram : public DILocalScope {
DIType *getContainingType() const {
return cast_or_null<DIType>(getRawContainingType());
}
+ void replaceType(DISubroutineType *Ty) {
+ assert(isDistinct() && "Only distinct nodes can mutate");
+ replaceOperandWith(4, Ty);
+ }
DICompileUnit *getUnit() const {
return cast_or_null<DICompileUnit>(getRawUnit());
diff --git a/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp b/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
index ddc2d5b63de0f..5ba8fe9ddf4e8 100644
--- a/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
+++ b/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
@@ -23,6 +23,7 @@
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constants.h"
+#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
@@ -1073,6 +1074,16 @@ bool DeadArgumentEliminationPass::RemoveDeadStuffFromFunction(Function *F) {
for (auto MD : MDs)
NF->addMetadata(MD.first, *MD.second);
+ // If either the return value(s) or argument(s) are removed, then probably the
+ // function does not follow standard calling conventions anymore. Hence add
+ // DW_CC_nocall to DISubroutineType to inform debugger that it may not safe to
+ // call this function or try to interpret the return value.
+ if (NFTy != FTy && NF->getSubprogram()) {
+ DISubprogram *SP = NF->getSubprogram();
+ auto Temp = SP->getType()->cloneWithCC(llvm::dwarf::DW_CC_nocall);
+ SP->replaceType(MDNode::replaceWithPermanent(std::move(Temp)));
+ }
+
// Now that the old function is dead, delete it.
F->eraseFromParent();
diff --git a/llvm/test/Transforms/DeadArgElim/2010-04-30-DbgInfo.ll b/llvm/test/Transforms/DeadArgElim/2010-04-30-DbgInfo.ll
index 0056962d02f06..047545a8115a1 100644
--- a/llvm/test/Transforms/DeadArgElim/2010-04-30-DbgInfo.ll
+++ b/llvm/test/Transforms/DeadArgElim/2010-04-30-DbgInfo.ll
@@ -1,9 +1,12 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature
; RUN: opt -S -passes=deadargelim < %s | FileCheck %s
+; Apart from checking if debug metadata is correctly propagated, this also tests whether DW_CC_nocall
+; calling convention is added when either return values or arguments are removed.
+
@.str = private constant [1 x i8] zeroinitializer, align 1 ; <[1 x i8]*> [#uses=1]
-define i8* @vfs_addname(i8* %name, i32 %len, i32 %hash, i32 %flags) nounwind ssp {
+define i8* @vfs_addname(i8* %name, i32 %len, i32 %hash, i32 %flags) nounwind ssp !dbg !1 {
;
entry:
call void @llvm.dbg.value(metadata i8* %name, metadata !0, metadata !DIExpression()), !dbg !DILocation(scope: !1)
@@ -17,7 +20,7 @@ entry:
declare void @llvm.dbg.declare(metadata, metadata, metadata) nounwind readnone
-define internal fastcc i8* @add_name_internal(i8* %name, i32 %len, i32 %hash, i8 zeroext %extra, i32 %flags) noinline nounwind ssp {
+define internal fastcc i8* @add_name_internal(i8* %name, i32 %len, i32 %hash, i8 zeroext %extra, i32 %flags) noinline nounwind ssp !dbg !16 {
;
entry:
call void @llvm.dbg.value(metadata i8* %name, metadata !15, metadata !DIExpression()), !dbg !DILocation(scope: !16)
@@ -64,7 +67,10 @@ declare void @llvm.dbg.value(metadata, metadata, metadata) nounwind readnone
!13 = !DILocation(line: 13, scope: !14)
!14 = distinct !DILexicalBlock(line: 12, column: 0, file: !28, scope: !1)
!15 = !DILocalVariable(name: "name", line: 17, arg: 1, scope: !16, file: !2, type: !6)
+; CHECK: !DISubprogram(name: "add_name_internal"
+; CHECK-SAME: type: ![[MD:[0-9]+]]
!16 = distinct !DISubprogram(name: "add_name_internal", linkageName: "add_name_internal", line: 22, isLocal: true, isDefinition: true, virtualIndex: 6, isOptimized: false, unit: !3, file: !28, scope: !2, type: !17)
+; CHECK: ![[MD]] = !DISubroutineType(cc: DW_CC_nocall, types: !{{[0-9]+}})
!17 = !DISubroutineType(types: !18)
!18 = !{!6, !6, !9, !9, !19, !9}
!19 = !DIBasicType(tag: DW_TAG_base_type, name: "unsigned char", size: 8, align: 8, encoding: DW_ATE_unsigned_char)
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