https://llvm.org/bugs/show_bug.cgi?id=30309
Bug ID: 30309
Summary: [KNL] Wrong instruction generated in while-condition
Product: clang
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: LLVM Codegen
Assignee: unassignedclangb...@nondot.org
Reporter: ilia.tara...@intel.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
==============test.c=================
#include "stdio.h"
int main(){
int k = 0, x = 1;
while((k > 0) && (x > 0))
{
printf("4\n");
}
return 0;
}
======================================
>>>clang -v
clang version 4.0.0 (cfe/trunk 280679)
...
>>>clang test.c
>>>./a.out
no output
>>>clang -march=knl test.c
>>>sde -knl -- ./a.out
>>>4
>>>4
>>>4
....
=======generated-while-assembler========
40051d: 31 c0 xor %eax,%eax
40051f: 88 c1 mov %al,%cl <- moving
zero to cl
400521: 83 7d f8 00 cmpl $0x0,-0x8(%rbp)
400525: c5 f8 92 c1 kmovw %ecx,%k0 <- coping
full cx to k0, not only zero
400529: c5 f8 91 45 f2 kmovw %k0,-0xe(%rbp)
40052e: 0f 8e 16 00 00 00 jle 40054a <main+0x4a>
400534: 8b 45 f4 mov -0xc(%rbp),%eax
400537: 85 c0 test %eax,%eax
400539: 0f 9f c1 setg %cl
40053c: 88 c8 mov %cl,%al
40053e: 83 e0 01 and $0x1,%eax
400541: c5 f8 92 c0 kmovw %eax,%k0
400545: c5 f8 91 45 f2 kmovw %k0,-0xe(%rbp)
40054a: c5 f8 90 45 f2 kmovw -0xe(%rbp),%k0
40054f: c5 f8 98 c0 kortestw %k0,%k0 <- as
result, no zero in k0
400553: 0f 85 05 00 00 00 jne 40055e <main+0x5e>
400559: e9 19 00 00 00 jmpq 400577 <main+0x77>
=========================================
------------------------
Intel Software Engineer
Ilia Taraban
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