[llvm-bugs] [Bug 31319] New: codegen difference at -O0 depending on whether -g is specified

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=31319

            Bug ID: 31319
           Summary: codegen difference at -O0 depending on whether -g is
                    specified
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: X86
          Assignee: unassignedb...@nondot.org
          Reporter: greg_bedw...@sn.scee.net
                CC: florian.h...@arm.com, llvm-bugs@lists.llvm.org
    Classification: Unclassified

Since "r288794 - [framelowering] Improve tracking of first CS pop instruction."
we've spotted the following codegen difference depending on whether -g is
specified or not using the tools/clang/utils/check_cfc tool:

$ clang --version
clang version 4.0.0 (http://llvm.org/git/clang.git
45e06a61601c5455359b9a4810b0c26937417bac) (http://llvm.org/git/llvm.git
c153f037fe7028dc845c23c93056ef89ec7074f0)
Target: x86_64-scei-ps4
Thread model: posix
InstalledDir:
c:\work\public-git\upstream-llvm\build-vs2015-ps4-master\Release\bin

$ cat test.c
struct Buffer {
  char flags;
} __attribute__((aligned(64)));
void fn1(struct Buffer p1) {}

$ cat test.sh
#!/bin/bash -xe
CFLAGS=-O0
clang -c $CFLAGS test.c -o test.o
llvm-objdump -d test.o > test.od
clang -c $CFLAGS test.c -o test.o -g
llvm-objdump -d test.o > testg.od
diff test.od testg.od

$ sh test.sh
9,11c9,12
<        8:     48 89 ec        movq    %rbp, %rsp
<        b:     5d      popq    %rbp
<        c:     c3      retq
---
>        8:     48 83 ec 40     subq    $64, %rsp
>        c:     48 89 ec        movq    %rbp, %rsp
>        f:     5d      popq    %rbp
>       10:     c3      retq

$

~~

With the previous revision:

$ clang --version
clang version 4.0.0 (http://llvm.org/git/clang.git
45e06a61601c5455359b9a4810b0c26937417bac) (http://llvm.org/git/llvm.git
ec5ae20d531eef4431e99534f68813980836220e)
Target: x86_64-scei-ps4
Thread model: posix
InstalledDir:
c:\work\public-git\upstream-llvm\build-vs2015-ps4-master\Release\bin

$ sh test.sh

$

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