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Issue
8479017:
Add a compatibility function attribute (and flag) for nacl-gcc to (Closed)
DescriptionAdd a compatibility function attribute (and flag) for nacl-gcc to
be ABI compatible with llvm/PNaCl.
Due to the fact that llvm bitcode loses information about the original source,
(unions, alignment) it is hard to match the ABI (see notes for known issues:
https://docs.google.com/a/google.com/document/d/1P3WrT_LHwN20gbs75LnHuMrbd804fSdSHKGK7Q3B20k/edit?hl=en_US#bookmark=id.sb20hms96tga).
Thus, for now, we make an attribute (and flag) to pass and return
structures and unions on the stack. Vectors and scalars can still use registers. This is calling convention is easy
to match. With this nacl-gcc is calling convention compatible with
pnacl. If at some point in the future we get richer type information
in bitcode we could do without this.
*****
Example uses of the attribute:
typedef struct {int x; float y; } s1;
typedef void (__attribute__((pnaclcall)) *pnacl_fp)(int, s1, int);
typedef s1 (__attribute__((pnaclcall)) *pnacl_ret_fp)(int, int) ;
extern void foo(int x, s1 y, int z);
__attribute__((pnaclcall)) void bar(int x, s1 y, int z)
{
foo(x, y, z);
if (x > 0)
bar(x - 1, y, z);
}
void bar_fp_casted(void) {
s1 s = { 80, 81.0f };
void (__attribute__((pnaclcall)) *temp_fp)(int, s1, int) ;
temp_fp = (pnacl_fp)&foo;
(*temp_fp)(79, s, 82);
}
void bar_fp_casted2(void) {
s1 s = { 80, 81.0f };
void (*temp_fp)(int, s1, int) = &foo;
(*(pnacl_fp)temp_fp)(79, s, 82);
}
*****
BUG= http://code.google.com/p/nativeclient/issues/detail?id=1819
BUG= http://code.google.com/p/nativeclient/issues/detail?id=2413
TEST= http://codereview.chromium.org/8502006/
and toolchain trybots
Committed: http://git.chromium.org/gitweb?p=native_client/nacl-gcc.git;a=commit;h=82ea71e
Patch Set 1 #Patch Set 2 : remove debug printf #Patch Set 3 : Hack for propagating attributes from a function pointer, when determining how structs are returned. #Patch Set 4 : indent #Patch Set 5 : Fix var-args #
Total comments: 10
Patch Set 6 : style changes #Patch Set 7 : more spacing #Patch Set 8 : braces #Patch Set 9 : period #
Messages
Total messages: 7 (0 generated)
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