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Fix sub-int returns on x86-64 and i386

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the ABIs (and other compilers) extend sub-int return values in the
caller.  TCC extends them in the callee.  For compatibility with
those other compilers we have extend them in the caller as well.
That introduces a useless double extension in pure TCC-compiled code,
but fixing that generally requires that the code generator of TCC would
understand sub-int types.  For the time being bite the bullet.
This commit is contained in:
Michael Matz 2019-02-10 18:27:41 +01:00
parent 5f737fb4d3
commit 749d19d70b
2 changed files with 18 additions and 2 deletions
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1
i386-gen.c
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@ -369,6 +369,7 @@ static void gcall_or_jmp(int is_jmp)
rt = vtop->type.ref->type.t;
switch (rt & VT_BTYPE) {
case VT_BYTE:
case VT_BOOL:
if (rt & VT_UNSIGNED) {
o(0xc0b60f); /* movzx %al, %eax */
}

19
x86_64-gen.c
View File

@ -920,7 +920,7 @@ void gfunc_call(int nb_args)
/* other compilers don't clear the upper bits when returning char/short */
bt = vtop->type.ref->type.t & (VT_BTYPE | VT_UNSIGNED);
if (bt == (VT_BYTE | VT_UNSIGNED))
if (bt == (VT_BYTE | VT_UNSIGNED) || (bt & VT_TYPE) == VT_BOOL)
o(0xc0b60f); /* movzbl %al, %eax */
else if (bt == VT_BYTE)
o(0xc0be0f); /* movsbl %al, %eax */
@ -1230,7 +1230,7 @@ void gfunc_call(int nb_args)
{
X86_64_Mode mode;
CType type;
int size, align, r, args_size, stack_adjust, i, reg_count;
int size, align, r, args_size, stack_adjust, i, reg_count, bt;
int nb_reg_args = 0;
int nb_sse_args = 0;
int sse_reg, gen_reg;
@ -1413,6 +1413,21 @@ void gfunc_call(int nb_args)
gcall_or_jmp(0);
if (args_size)
gadd_sp(args_size);
/* other compilers don't clear the upper bits when returning char/short,
TCC does so for convenience. When we'd stay purely within TCC compiled
code we wouldn't need this, but for compatibility we have to extend.
Ideally TCC wouldn't extend at return statements to not do double
extensions, or would understand sub-int types during expression
evaluation. */
bt = vtop->type.ref->type.t & (VT_BTYPE | VT_UNSIGNED);
if (bt == (VT_BYTE | VT_UNSIGNED) || (bt & VT_TYPE) == VT_BOOL)
o(0xc0b60f); /* movzbl %al, %eax */
else if (bt == VT_BYTE)
o(0xc0be0f); /* movsbl %al, %eax */
else if (bt == VT_SHORT)
o(0x98); /* cwtl */
else if (bt == (VT_SHORT | VT_UNSIGNED))
o(0xc0b70f); /* movzwl %al, %eax */
vtop--;
}