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/* bug-3406.c
A bug in z80 code generation for pointer writes. Hard to trigger, since it requires specific registers to be in use for particular operands, and multiple others to be in use.
*/
#include <testfwk.h>
typedef unsigned char u8;
typedef unsigned short u16;
struct VDP_Command {
u16 DX, DY, NX;
u8 CLR;
};
struct VDP_Command g_VDP_Command;
u16 words[8];
u16* pwords = words;
void my_VPD_CommandSetupR36( void ) {
*pwords++ = g_VDP_Command.NX;
}
// HERE: VDP_CommandLMMV(x, y, pixelWidth_FAILS, src->Red );
inline void VDP_CommandLMMV(u16 dx, u16 dy, u16 nx, u8 col)
{
g_VDP_Command.DX = dx;
g_VDP_Command.DY = dy; // For this line, the order of register saves to stack is incompatible with restoring them.
g_VDP_Command.NX = nx;
g_VDP_Command.CLR = col;
my_VPD_CommandSetupR36();
}
struct ScreenSetting {
u16 Width;
u8 Red;
};
const struct ScreenSetting g_Settings[] = { {
256, // <===== WIDTH
17
},
};
void InitScreen( void ) {
const struct ScreenSetting* src = &g_Settings[0];
u8 pixelWidth = src->Width / 256;
VDP_CommandLMMV(0, 0, src->Width, 0);
for(u8 i = 0; i < 2; ++i) {
u16 x = 19 % src->Width;
u16 y = x & 1;
VDP_CommandLMMV(x, y, pixelWidth, src->Red);
VDP_CommandLMMV(x, y, pixelWidth, src->Red);
}
}
void testBug( void ) {
InitScreen();
ASSERT(words[0] == 0x0100);
ASSERT(words[1] == 1); // 0x1110 when bug is present
ASSERT(words[2] == 1);
ASSERT(words[3] == 1); // 0x1110 when bug is present
ASSERT(words[4] == 1);
}
extern void VDP_CommandLMMV(u16 dx, u16 dy, u16 nx, u8 col);
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