https://bugs.llvm.org/show_bug.cgi?id=49446
Bug ID: 49446
Summary: Backward copy propagation failed w/ -g
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Common Code Generator Code
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Created attachment 24590
--> https://bugs.llvm.org/attachment.cgi?id=24590&action=edit
The hot.cc is generated by creduce
To reproduce
> clang++ -c hot.cc -o dbg.o -O3 -g
> clang++ -c hot.cc -o rel.o -O3
Then diff the objdump outputs.
- c2: 48 8d 6c 24 28 lea 0x28(%rsp),%rbp
- c7: 48 89 eb mov %rbp,%rbx
- ca: 0f 11 45 00 movups %xmm0,0x0(%rbp)
+ c2: 48 8d 5c 24 28 lea 0x28(%rsp),%rbx
+ c7: 0f 11 03 movups %xmm0,(%rbx)
+ ca: 8b 44 24 20 mov 0x20(%rsp),%eax
For those two instructions:
lea 0x28(%rsp), %rbp
mov %rbp, %rbx
can be applied with backward copy propagation to eliminate the rbp register.
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