http://llvm.org/bugs/show_bug.cgi?id=14023
Bug #: 14023
Summary: Loop unroller and other passes fail to update Debugger
information for register-mapped variables
Product: libraries
Version: trunk
Platform: All
OS/Version: All
Status: NEW
Severity: normal
Priority: P
Component: Core LLVM classes
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Classification: Unclassified
The loop unroller fails to update the "call @llvm.dbg.value" instructions as it
unrolls the body of a loop. Thus, the generated dwarf does not properly track
the value of any register-based variable that is updated on each iteration of
the loop.
Test case:
int sum(int *vector){
int result = 0;
for (int i = 0; i < 8; i++){
result += vector[i];
}
return result;
}
Bitcode output at -O3 (x86 target):
define i32 @sum(i32* nocapture %vector) nounwind readonly {
entry:
tail call void @llvm.dbg.value(metadata !{i32* %vector}, i64 0, metadata !13),
!dbg !18
tail call void @llvm.dbg.value(metadata !2, i64 0, metadata !14), !dbg !19
tail call void @llvm.dbg.value(metadata !2, i64 0, metadata !16), !dbg !20
%0 = load i32* %vector, align 4, !dbg !21, !tbaa !23
tail call void @llvm.dbg.value(metadata !{i32 %0}, i64 0, metadata !14), !dbg
!21
tail call void @llvm.dbg.value(metadata !26, i64 0, metadata !16), !dbg !27
%arrayidx.1 = getelementptr inbounds i32* %vector, i32 1, !dbg !21
%1 = load i32* %arrayidx.1, align 4, !dbg !21, !tbaa !23
%add.1 = add nsw i32 %1, %0, !dbg !21
>>>WRONG: the following should be "!{i32 %add.1}"
tail call void @llvm.dbg.value(metadata !{i32 %0}, i64 0, metadata !14), !dbg
!21
>>>WRONG: below !26 is !{i32 1} Should be !{i32 2}
tail call void @llvm.dbg.value(metadata !26, i64 0, metadata !16), !dbg !27
%arrayidx.2 = getelementptr inbounds i32* %vector, i32 2, !dbg !21
%2 = load i32* %arrayidx.2, align 4, !dbg !21, !tbaa !23
%add.2 = add nsw i32 %2, %add.1, !dbg !21
>>>WRONG:the following should be "!{i32 %add.2}"
tail call void @llvm.dbg.value(metadata !{i32 %0}, i64 0, metadata !14), !dbg
!21
>>>WRONG: below !26 is !{i32 1}. Should be !{i32 3}
tail call void @llvm.dbg.value(metadata !26, i64 0, metadata !16), !dbg !27
... etc.
The problem appears to be systemic with metadata references to virtual
registers. Such registers do not appear as "uses"; therefore, they don't get
updated as optimizations occur. Not only does the loop unroller exhibit this
problem, but so does the Loop Rotate pass, the Loop Strength Reduce pass, and
any other pass that remaps virtual registers that correspond to local
variables.
--
Configure bugmail: http://llvm.org/bugs/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.
_______________________________________________
LLVMbugs mailing list
[email protected]
http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs
