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Added Opt_a_tossub for 8-bit subtraction.

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acqn 2021-02-05 17:29:49 +08:00
parent bb1b5c363e
commit 6617a017fa
1 changed files with 53 additions and 0 deletions
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53
src/cc65/coptstop.c
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@ -1292,6 +1292,58 @@ static unsigned Opt_a_tosne (StackOpData* D)
static unsigned Opt_a_tossub (StackOpData* D)
/* Optimize the tossubax sequence. */
{
CodeEntry* X;
/* Inline the sbc */
D->IP = D->OpIndex+1;
/* Must be true because of OP_RHS_LOAD */
CHECK ((D->Rhs.A.Flags & D->Rhs.X.Flags & LI_DIRECT) != 0);
/* sec */
X = NewCodeEntry (OP65_SEC, AM65_IMP, 0, 0, D->OpEntry->LI);
InsertEntry (D, X, D->IP++);
/* Add code for low operand */
AddOpLow (D, OP65_SBC, &D->Rhs);
/* Do sign-extension as high-byte operation only when its result is used */
if ((GetRegInfo (D->Code, D->IP, REG_X) & REG_X) != 0) {
CodeLabel* L;
CodeEntry* N;
X = NewCodeEntry (OP65_LDX, AM65_IMM, MakeHexArg (0), 0, D->OpEntry->LI);
InsertEntry (D, X, D->IP++);
/* Add sign extension - N is unused now */
N = CS_GetEntry (D->Code, D->IP);
CHECK (N != 0);
L = CS_GenLabel (D->Code, N);
X = NewCodeEntry (OP65_BCS, AM65_BRA, L->Name, L, D->OpEntry->LI);
InsertEntry (D, X, D->IP++);
X = NewCodeEntry (OP65_DEX, AM65_IMP, 0, 0, D->OpEntry->LI);
InsertEntry (D, X, D->IP++);
}
/* Rhs load entries must be removed */
D->Rhs.X.Flags |= LI_REMOVE;
D->Rhs.A.Flags |= LI_REMOVE;
/* Remove the push and the call to the tossubax function */
RemoveRemainders (D);
/* We changed the sequence */
return 1;
}
static unsigned Opt_a_tosuge (StackOpData* D)
/* Optimize the tosgeax and tosugeax sequences */
{
@ -1363,6 +1415,7 @@ static const OptFuncDesc FuncRegATable[] = {
{ "tosleax", Opt_a_tosule, REG_NONE, OP_NONE },
{ "tosltax", Opt_a_tosult, REG_NONE, OP_NONE },
{ "tosneax", Opt_a_tosne, REG_NONE, OP_NONE },
{ "tossubax", Opt_a_tossub, REG_NONE, OP_RHS_REMOVE_DIRECT | OP_RHS_LOAD_DIRECT },
{ "tosugeax", Opt_a_tosuge, REG_NONE, OP_NONE },
{ "tosugtax", Opt_a_tosugt, REG_NONE, OP_NONE },
{ "tosuleax", Opt_a_tosule, REG_NONE, OP_NONE },