| Issue |
132934
|
| Summary |
[X64] Inst combine Pass bug - Incorrect combining lost memory de-reference
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
IshwaraK
|
The inst-combine is doing incorrect combining for the below code. Instead of de-referencing and then accessing the memory, it did offset addition and accessed wrong memory address.
The CE link is here https://godbolt.org/z/G8e6GrKW8
```
typedef unsigned char ub1;
typedef unsigned short ub2;
typedef unsigned int ub4;
typedef int boolean;
struct spStruct
{
ub4 phySize;
void *hSize;
};
typedef struct spStruct spStruct;
struct kccStruct {
ub4 kfhdbi;
ub4 kfhcsq;
ub4 kfhfsz; // till here size = 12 bytes
ub4 kbsz;
}; // Size = 16 bytes
typedef struct kccStruct kccStruct;
struct kBlkStruct
{
kccStruct fh_blk;
ub4 offset;
ub4 amount;
ub4 modtime;
};
typedef struct kBlkStruct kBlkStruct;
struct kStruct {
ub1 tVar1;
ub1 tVar2;
ub2 tVar3;
ub4 tVar4;
}; // size = 8 bytes
typedef struct kStruct kStruct;
void foo(spStruct *spPointer) {
spPointer->phySize =
((kBlkStruct *)((ub1 *)spPointer->hSize + sizeof(kStruct)))
->fh_blk.kbsz;
}
```
```
define dso_local void @foo(spStruct*)(ptr nocapture noundef initializes((0, 4)) %0) local_unnamed_addr #0 !dbg !32 {
#dbg_value(ptr %0, !43, !DIExpression(), !44)
%2 = getelementptr inbounds nuw i8, ptr %0, i64 8, !dbg !45
%3 = load ptr, ptr %2, align 8, !dbg !45
%4 = getelementptr inbounds nuw i8, ptr %3, i64 20, !dbg !52 ; <---- Wrong, lost de-referencing via (kBlkStruct *); instead combined offset addition as 8 + 12 = 20 bytes. This lead to wrong memory slot
%5 = load i32, ptr %4, align 4, !dbg !52
store i32 %5, ptr %0, align 8, !dbg !56
ret void, !dbg !58
}
```
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