[Bug 227723] clang 6.0 breaks php56/opcache

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=227723

--- Comment #4 from lampa at fit.vutbr.cz ---
test case was for constant, which was optimized to immediate, here is another
with variable:

#include <stdio.h>
#include <stdlib.h>

#define EX_TMP_VAR(ex, n)         ((temp_variable*)(((char*)(ex)) +
((int)(n))))
#define EX_TMP_VAR_NUM(ex, n)  (EX_TMP_VAR(ex, 0) - (1 + (n)))
#define VAR_NUM(v) ((unsigned int)(EX_TMP_VAR_NUM(0, 0) - EX_TMP_VAR(0, v)))

typedef struct TV {
        long tmp;
        char tmp3[30];
} temp_variable;

int num = -1000;

int main()
{
        printf("%x\n", VAR_NUM(num));
        return 0;
}

clang50 result is 18
clang60 result is 60000018

The only difference in generated code (clang50 first, clang60 second):

<       movslq  num(%rip), %rax
---
>       movl    num(%rip), %eax
        movq    $-40, %rcx
        subq    %rax, %rcx
        shrq    $3, %rcx


It looks like num is not sign extended before pointer arithmetic.

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