https://bugs.llvm.org/show_bug.cgi?id=39019
Bug ID: 39019
Summary: [DebugInfo@O2][Dexter] Return value unprintable in
func with vectorized loop
Product: new-bugs
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Keywords: wrong-debug
Severity: normal
Priority: P
Component: new bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected],
[email protected],
[email protected]
Blocks: 38768
The vectorized-and-reduced summation below in variable 'sum' is reported as
optimized out on the return line, according to debug info. Given the value is
available in $rax we can almost certainly do better. My test setup is using
clang/llvm r342527, compiling "-O2 -g -fno-inline" targeting x86_64, and
running under gdb or lldb.
If you change BUFSZ to be 193 then the vectorized loop gets a scalar tail,
which contains the original body with dbg.value's, and the 'sum' variable is
printable on the return line.
(This is the same code as in bug 39018, but a different issue).
-------->8--------
#include <string.h>
#define BUFSZ 192
int
main()
{
int foo[BUFSZ];
int bar[BUFSZ];
memset(foo, 0, sizeof(foo));
memset(bar, 1, sizeof(bar));
for (int i = 0; i < BUFSZ; i++)
foo[i] += bar[i];
unsigned int sum = 0;
for (int j = 0; j < BUFSZ; j++)
sum += foo[j];
return sum;
}
--------8<--------
Referenced Bugs:
https://bugs.llvm.org/show_bug.cgi?id=38768
[Bug 38768] [meta][DebugInfo] Umbrella bug for poor debug experiences
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