http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56114
Bug #: 56114
Summary: x86_64-linux-gnu-gcc generate wrong asm instruction
MOVABS for intel syntax
Classification: Unclassified
Product: gcc
Version: 4.7.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: [email protected]
ReportedBy: [email protected]
For example file l.c
long foo2 (void)
{
return *(volatile long*)0xFEE00000;
}
x86_64-linux-gnu-gcc -c -save-temps l.c -O2 -masm=intel
cat l.s
.file "l.c"
.intel_syntax noprefix
.text
.p2align 4,,15
.globl foo2
.type foo2, @function
foo2:
.LFB0:
.cfi_startproc
movabs rax, 4276092928
ret
This is erroneous instruction, because movabs rax, 4276092928 loads immediate
data. This code must be
movabs rax, [4276092928]
with square brackets.
When we try to read 32-bit data from memory, then we get error message
long foo2 (void)
{
return *(volatile int*)0xFEE00000;
}
x86_64-linux-gnu-gcc -c -save-temps l.c -O2 -masm=intel
cat l.s
.file "l.c"
.intel_syntax noprefix
.text
.p2align 4,,15
.globl foo2
.type foo2, @function
foo2:
.LFB0:
.cfi_startproc
movabs eax, 4276092928
cdqe
ret
Because movabs allows load 64-bit only immediate data. Here is GCC loose square
brackets.
