https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64895
Bug ID: 64895
Summary: [5 Regression] RA picks the wrong register for
-fipa-ra
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: hjl.tools at gmail dot com
CC: vmakarov at redhat dot com
'-fipa-ra'
Use caller save registers for allocation if those registers are not
used by any called function. In that case it is not necessary to
save and restore them around calls. This is only possible if
called functions are part of same compilation unit as current
function and they are compiled before it.
But in this case testcase
[hjl@gnu-tools-1 gcc]$ cat /tmp/x.c
static int __attribute__((noinline))
bar (int x)
{
if (x > 4)
return bar (x - 3);
return 0;
}
int __attribute__((noinline))
foo (int y)
{
return y + bar (y);
}
[hjl@gnu-tools-1 gcc]$ ./xgcc -B./ -m32 -fpic -O2 -fipa-ra -fomit-frame-pointer
-fno-optimize-sibling-calls -mregparm=1 /tmp/x.c -S
-fno-asynchronous-unwind-tables
[hjl@gnu-tools-1 gcc]$ cat x.s
.file "x.c"
.section .text.unlikely,"ax",@progbits
.LCOLDB0:
.text
.LHOTB0:
.p2align 4,,15
.type bar, @function
bar:
cmpl $4, %eax
jg .L7
xorl %eax, %eax
ret
.p2align 4,,10
.p2align 3
.L7:
subl $12, %esp
subl $3, %eax
call bar
addl $12, %esp
ret
.size bar, .-bar
.section .text.unlikely
.LCOLDE0:
.text
.LHOTE0:
.section .text.unlikely
.LCOLDB1:
.text
.LHOTB1:
.p2align 4,,15
.globl foo
.type foo, @function
foo:
pushl %ebx
movl %eax, %ebx
subl $8, %esp
call bar
addl $8, %esp
addl %ebx, %eax
popl %ebx
ret
.size foo, .-foo
.section .text.unlikely
.LCOLDE1:
.text
.LHOTE1:
.ident "GCC: (GNU) 5.0.0 20150201 (experimental)"
.section .note.GNU-stack,"",@progbits
[hjl@gnu-tools-1 gcc]$
Pick EBX instead of EDX to save EAX in foo.
