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x86: Avoid using DX register as divisor #175

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8 changes: 4 additions & 4 deletions src/cowbe/arch8086.cow.ng
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Original file line number Diff line number Diff line change
Expand Up @@ -748,10 +748,10 @@ gen al := REMU1(al, mem1|bl|cl|dl:rhs) { E("\txor ah, ah\n"); E_insn("di
gen al := DIVS1(al, mem1|bl|cl|dl:rhs) { E("\tcbw\n"); E_insn("idiv"); E_op0($rhs, &$@rhs.operand); E_nl(); }
gen al := REMS1(al, mem1|bl|cl|dl:rhs) { E("\tcbw\n"); E_insn("idiv"); E_op0($rhs, &$@rhs.operand); E_nl(); E("\tmov al, ah\n"); }

gen ax := DIVU2(ax, mem2|bx|cx|dx:rhs) uses dx { E("\txor dx, dx\n"); E_insn("div"); E_op0($rhs, &$@rhs.operand); E_nl(); }
gen dx := REMU2(ax, mem2|bx|cx|dx:rhs) { E("\txor dx, dx\n"); E_insn("div"); E_op0($rhs, &$@rhs.operand); E_nl(); }
gen ax := DIVS2(ax, mem2|bx|cx|dx:rhs) uses dx { E("\tcwd\n"); E_insn("idiv"); E_op0($rhs, &$@rhs.operand); E_nl(); }
gen dx := REMS2(ax, mem2|bx|cx|dx:rhs) { E("\tcwd\n"); E_insn("idiv"); E_op0($rhs, &$@rhs.operand); E_nl(); }
gen ax := DIVU2(ax, mem2|bx|cx|di|si:rhs) uses dx { E("\txor dx,dx\n"); E_insn("div"); E_op0($rhs, &$@rhs.operand); E_nl(); }
gen dx := REMU2(ax, mem2|bx|cx|di|si:rhs) { E("\txor dx,dx\n"); E_insn("div"); E_op0($rhs, &$@rhs.operand); E_nl(); }
gen ax := DIVS2(ax, mem2|bx|cx|di|si:rhs) uses dx { E("\tcwd\n"); E_insn("idiv"); E_op0($rhs, &$@rhs.operand); E_nl(); }
gen dx := REMS2(ax, mem2|bx|cx|di|si:rhs) { E("\tcwd\n"); E_insn("idiv"); E_op0($rhs, &$@rhs.operand); E_nl(); }

gen al|bl|dl := LSHIFT1($$:lhs, cl:rhs) { E_insn("shl"); E_reg($lhs); E(", cl\n"); }
gen ax|bx|dx|si|di := LSHIFT2($$:lhs, cl:rhs) { E_insn("shl"); E_reg($lhs); E(", cl\n"); }
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4 changes: 4 additions & 0 deletions tests/divrem-16bit-s.good
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Expand Up @@ -2,6 +2,10 @@
-7/3=-2: yes
7/-3=-2: yes
-7/-3=2: yes
7/THREE=2: yes
-7/THREE=-2: yes
7/-THREE=-2: yes
-7/-THREE=2: yes
7%3=1: yes
-7%3=-1: yes
7%-3=1: yes
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5 changes: 5 additions & 0 deletions tests/divrem-16bit-s.test.cow
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Expand Up @@ -11,6 +11,11 @@ print("-7/3=-2"); if mseven/three == -2 then yes(); else no(); end if;
print("7/-3=-2"); if seven/mthree == -2 then yes(); else no(); end if;
print("-7/-3=2"); if mseven/mthree == 2 then yes(); else no(); end if;

print("7/THREE=2");if (seven/3) == 2 then yes(); else no(); end if;
print("-7/THREE=-2");if (mseven/3) == -2 then yes(); else no(); end if;
print("7/-THREE=-2");if (seven/-3) == -2 then yes(); else no(); end if;
print("-7/-THREE=2");if (mseven/-3) == 2 then yes(); else no(); end if;

print("7%3=1"); if seven%three == 1 then yes(); else no(); end if;
print("-7%3=-1"); if mseven%three == -1 then yes(); else no(); end if;
print("7%-3=1"); if seven%mthree == 1 then yes(); else no(); end if;
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