https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71428
Bug ID: 71428
Summary: [7 Regression] wrong code with -Os -fno-tree-forwprop
(breaks in the .bswap dump)
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: zsojka at seznam dot cz
Target Milestone: ---
Compiler output:
$ x86_64-pc-linux-gnu-gcc -Os -fno-tree-forwprop testcase.c -Wno-psabi
$ ./a.out
Aborted
Diffing 6-branch and trunk assembly output shows:
@@ -7,10 +7,10 @@
.LFB0:
.cfi_startproc
mov dx, WORD PTR [rsp+10]
- or WORD PTR [rsp+70], dx
mov rax, rdi
lea rsi, [rsp+8]
mov ecx, 16
+ mov WORD PTR [rsp+70], dx
rep movsd
ret
.cfi_endproc
The "or" seems to disappear in the .bswap dump in trunk.
6-branch .bswap doesn't perform any transformation, but trunk's one does.
