http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60856
Bug ID: 60856
Summary: GCC4.9 inline-asm has wrong register allocation for
MIPS64r2
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: qiuji at loongson dot cn
Created attachment 32612
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32612&action=edit
preprocessed file of the wrong case
In test.c piece of inline assemmble instructions are written to work as the c
code above them.
the C code is :
if (a < b) {
x = a;
y = b - a + 1;
} else {
x = b;
y = a - b + 1;
}
the inline asm is:
asm(
" .set mips64r2 \r\n"
" .set noreorder \r\n"
" slt $8, %2, %3 \r\n"
" move %0, %2 \r\n"
" sub $9, %3, %2 \r\n"
" addi %1,$9, 1 \r\n"
" movz %0, %3, $8 \r\n"
" sub $10, %2, %3 \r\n"
" addi $10, 1 \r\n"
" movz %1, $10, $8 \r\n"
" .set reorder \r\n"
:"=r"(x), "=r"(y)
:"r"(a), "r"(b)
:"$8","$9", "$10"
);
And the final code I got from the GCC4.9 in the .s file is:
.set mips64r2
.set noreorder
slt $8, $2, $3
move $4, $2
sub $9, $3, $2
addi $3,$9, 1
movz $4, $3, $8
sub $10, $2, $3
addi $10, 1
movz $3, $10, $8
.set reorder
the "r"(b) variable is allocated to $3 while "=r"(y) variable is also allocated
to $3. That makes wrong result.
