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* on i8086 with regvars on, do not notify the register allocator of moves to BX.

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This fixes compilation of unit math (and the whole RTL) with regvars enabled.

git-svn-id: trunk@26282 -
This commit is contained in:
nickysn 2013-12-25 12:19:21 +00:00
parent e6a9bfdc1d
commit fdd36b4603
1 changed files with 68 additions and 0 deletions
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68
compiler/i8086/cgcpu.pas
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@ -89,6 +89,8 @@ unit cgcpu;
procedure g_intf_wrapper(list: TAsmList; procdef: tprocdef; const labelname: string; ioffset: longint);override;
procedure get_32bit_ops(op: TOpCG; out op1,op2: TAsmOp);
procedure add_move_instruction(instr:Taicpu);override;
end;
tcg64f8086 = class(tcg64f32)
@ -1630,6 +1632,72 @@ unit cgcpu;
end;
procedure tcg8086.add_move_instruction(instr: Taicpu);
begin
{ HACK: when regvars are on, don't notify the register allocator of any
direct moves to BX, so it doesn't try to coalesce them. Currently,
direct moves to BX are only used when returning an int64 value in
AX:BX:CX:DX. This hack fixes a common issue with functions, returning
int64, for example:
function RandomFrom(const AValues: array of Int64): Int64;
begin
result:=AValues[random(High(AValues)+1)];
end;
push bp
mov bp,sp
; Var AValues located in register ireg20w
; Var $highAVALUES located in register ireg21w
; Var $result located in register ireg33w:ireg32w:ireg31w:ireg30w
mov ireg20w,word [bp+6]
mov ireg21w,word [bp+4]
; [3] result:=AValues[random(High(AValues)+1)];
mov ireg22w,ireg21w
inc ireg22w
mov ax,ireg22w
cwd
mov ireg23w,ax
mov ireg24w,dx
push ireg24w
push ireg23w
call SYSTEM_$$_RANDOM$LONGINT$$LONGINT
mov ireg25w,ax
mov ireg26w,dx
mov ireg27w,ireg25w
mov ireg28w,ireg27w
mov ireg29w,ireg28w
mov cl,3
shl ireg29w,cl
; Var $result located in register ireg32w:ireg30w
mov ireg30w,word [ireg20w+ireg29w]
mov ireg31w,word [ireg20w+ireg29w+2]
mov ireg32w,word [ireg20w+ireg29w+4] ; problematic section start
mov ireg33w,word [ireg20w+ireg29w+6]
; [4] end;
mov bx,ireg32w ; problematic section end
mov ax,ireg33w
mov dx,ireg30w
mov cx,ireg31w
mov sp,bp
pop bp
ret 4
the problem arises, because the register allocator tries to coalesce
mov bx,ireg32w
however, in the references [ireg20w+ireg29w+const], due to the
constraints of i8086, ireg20w can only be BX (or BP, which isn't available
to the register allocator, because it's used as a base pointer) }
if (cs_opt_regvar in current_settings.optimizerswitches) and
(instr.opcode=A_MOV) and (instr.ops=2) and
(instr.oper[1]^.typ=top_reg) and (getsupreg(instr.oper[1]^.reg)=RS_BX) then
exit
else
inherited add_move_instruction(instr);
end;
procedure tcg8086.g_adjust_self_value(list:TAsmList;procdef: tprocdef;ioffset: tcgint);
var
hsym : tsym;