Trying your sample with mod on Windows -m64/-m32 I get: c: >tcc -m32 foo.c && foo 5.000000
c:>tcc -m64 foo.c && foo 5.000000 It only return 3.0000 on Linux x64 (I've not tested your code on Linux x86). C. -----Original Message----- From: Tinycc-devel [mailto:tinycc-devel-bounces+eligis=orange...@nongnu.org] On Behalf Of Shachaf Ben-Kiki Sent: Saturday, October 26, 2019 12:59 To: tinycc-devel@nongnu.org Subject: [Tinycc-devel] SSE calling convention bug Hello, I ran into a bug in the SSE function call code in x86_64-gen.c. It's in the following lines, in gfunc_call: if (sse_reg) { /* avoid redundant movaps %xmm0, %xmm0 */ /* movaps %xmm0, %xmmN */ o(0x280f); o(0xc0 + (sse_reg << 3)); /* movaps %xmm1, %xmmN */ o(0x280f); o(0xc1 + ((sse_reg+1) << 3)); } When sse_reg is %xmm1, this generates 0f 28 c8 movaps %xmm0,%xmm1 0f 28 d1 movaps %xmm1,%xmm2 Such that the first mov overwrites xmm1 before the second mov uses it. Since the registers are used in reverse order and only one or two at a time, I think swapping the order of the movs should be sufficient to fix it. Here's a test case: #include <stdio.h> struct Point { float x; float y; }; struct Rect { struct Point top_left; struct Point size; }; float foo(struct Point p, struct Rect r) { return r.size.x; } int main(int argc, char **argv) { struct Point p = {1, 2}; struct Rect r = {{3, 4}, {5, 6}}; printf("%f\n", foo(p, r)); return 0; } This program should print 5, but it prints 3 in tcc. Is this the right place to post this? I can post it elsewhere, or send a patch (it took a while to track this down but I think the fix should be easy). Thanks, Shachaf _______________________________________________ Tinycc-devel mailing list Tinycc-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/tinycc-devel _______________________________________________ Tinycc-devel mailing list Tinycc-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/tinycc-devel
