https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89523
Bug ID: 89523
Summary: Incorrect AVX instructions with VSIB address
Product: gcc
Version: 7.4.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: hjl.tools at gmail dot com
CC: ubizjak at gmail dot com
Target Milestone: ---
Target: x32
32-bit indices in VSIB address are sign-extended to 64 bits. In x32,
when 32-bit indices are used as addresses, like
%ymm7, 0(,%ymm6,1), %ymm0
0xf7fa3010 is sign-extended to 0xfffffffff7fa3010 which leads to
invalid address in x32.
Testcase:
[hjl@gnu-4 00000001]$ cat foo.i
void foo (void);
extern float *ncost;
float
bar (int type, int num)
{
int i;
float cost;
cost = 0;
for (i = 0; i < num; i++)
if (type)
cost += ncost[i];
else
foo ();
return (cost);
}
[hjl@gnu-4 00000001]$ gcc -S -mx32 -Ofast -funroll-loops -march=haswell foo.i
[hjl@gnu-4 00000001]$ grep gather foo.s
vgatherdps %ymm7, 0(,%ymm6,1), %ymm0
vgatherdps %ymm11, 0(,%ymm10,1), %ymm12
vgatherdps %ymm15, 0(,%ymm14,1), %ymm5
vgatherdps %ymm7, 0(,%ymm9,1), %ymm6
vgatherdps %ymm12, 0(,%ymm11,1), %ymm13
vgatherdps %ymm5, 0(,%ymm15,1), %ymm2
vgatherdps %ymm7, 0(,%ymm10,1), %ymm6
vgatherdps %ymm14, 0(,%ymm13,1), %ymm15
vgatherdps %ymm7, 0(,%ymm10,1), %ymm6
vgatherdps %ymm13, 0(,%ymm12,1), %ymm14
vgatherdps %ymm10, 0(,%ymm9,1), %ymm7
vgatherdps %ymm12, 0(,%ymm11,1), %ymm13
vgatherdps %ymm9, 0(,%ymm2,1), %ymm10
vgatherdps %ymm12, 0(,%ymm11,1), %ymm6
vgatherdps %ymm5, 0(,%ymm15,1), %ymm2
[hjl@gnu-4 00000001]$
