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* x86: TEST/Jcc/TEST optimisations can now look beyond the next instruction under -O3
This commit is contained in:
J. Gareth "Curious Kit" Moreton
FPK
parent
d372286159
commit
3f25438d35
@ -5223,7 +5223,7 @@ unit aoptx86;
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function TX86AsmOptimizer.OptPass1Test(var p: tai) : boolean;
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var
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hp1, p_label, p_dist, hp1_dist: tai;
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hp1, p_label, p_dist, hp1_dist, hp1_last: tai;
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JumpLabel, JumpLabel_dist: TAsmLabel;
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FirstValue, SecondValue: TCGInt;
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TempBool: Boolean;
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@ -5313,6 +5313,7 @@ unit aoptx86;
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{ Search for:
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test $x,(reg/ref)
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jne @lbl1
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...
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test $y,(reg/ref) (same register or reference)
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jne @lbl1
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@ -5327,6 +5328,7 @@ unit aoptx86;
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Also search for:
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test $x,(reg/ref)
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je @lbl1
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...
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test $y,(reg/ref)
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je/jne @lbl2
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@ -5355,106 +5357,167 @@ unit aoptx86;
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after it might (e.g. test; jne @lbl1; test; jne @lbl2; test @lbl1),
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so accommodate for this with a while loop.
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}
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hp1_dist := hp1;
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hp1_last := hp1;
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if GetNextInstruction(hp1, p_dist) and
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(p_dist.typ = ait_instruction) and
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(
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while (
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(
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(taicpu(p_dist).opcode = A_TEST) and
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(
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(taicpu(p_dist).oper[0]^.typ = top_const) or
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{ test %reg,%reg can be considered equivalent to test, -1,%reg }
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MatchOperand(taicpu(p_dist).oper[1]^, taicpu(p_dist).oper[0]^)
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)
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) or
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(
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{ cmp 0,%reg = test %reg,%reg }
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(taicpu(p_dist).opcode = A_CMP) and
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MatchOperand(taicpu(p_dist).oper[0]^, 0)
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)
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) and
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{ Make sure the destination operands are actually the same }
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MatchOperand(taicpu(p_dist).oper[1]^, taicpu(p).oper[1]^) and
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GetNextInstruction(p_dist, hp1_dist) and
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MatchInstruction(hp1_dist, A_JCC, []) then
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(taicpu(p).oper[1]^.typ = top_reg) and
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GetNextInstructionUsingReg(hp1_last, p_dist, taicpu(p).oper[1]^.reg)
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) or GetNextInstruction(hp1_last, p_dist)
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) and (p_dist.typ = ait_instruction) do
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begin
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if
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(taicpu(p_dist).opcode = A_CMP) { constant will be zero } or
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(
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(taicpu(p_dist).oper[0]^.typ = top_reg) and
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MatchOperand(taicpu(p_dist).oper[1]^, taicpu(p_dist).oper[0]^.reg)
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) then
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SecondValue := -1
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else
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SecondValue := taicpu(p_dist).oper[0]^.val;
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{ If both of the TEST constants are identical, delete the second
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TEST that is unnecessary. }
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if (FirstValue = SecondValue) then
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if (
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(
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(taicpu(p_dist).opcode = A_TEST) and
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(
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(taicpu(p_dist).oper[0]^.typ = top_const) or
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{ test %reg,%reg can be considered equivalent to test, -1,%reg }
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MatchOperand(taicpu(p_dist).oper[1]^, taicpu(p_dist).oper[0]^)
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)
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) or
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(
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{ cmp 0,%reg = test %reg,%reg }
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(taicpu(p_dist).opcode = A_CMP) and
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MatchOperand(taicpu(p_dist).oper[0]^, 0)
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)
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) and
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{ Make sure the destination operands are actually the same }
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MatchOperand(taicpu(p_dist).oper[1]^, taicpu(p).oper[1]^) and
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GetNextInstruction(p_dist, hp1_dist) and
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MatchInstruction(hp1_dist, A_JCC, []) then
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begin
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DebugMsg(SPeepholeOptimization + 'TEST/Jcc/TEST; removed superfluous TEST', p_dist);
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RemoveInstruction(p_dist);
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{ Don't let the flags register become deallocated and reallocated between the jumps }
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AllocRegBetween(NR_DEFAULTFLAGS, hp1, hp1_dist, UsedRegs);
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Result := True;
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if condition_in(taicpu(hp1_dist).condition, taicpu(hp1).condition) then
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if
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(taicpu(p_dist).opcode = A_CMP) { constant will be zero } or
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(
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(taicpu(p_dist).oper[0]^.typ = top_reg) and
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MatchOperand(taicpu(p_dist).oper[1]^, taicpu(p_dist).oper[0]^.reg)
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) then
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SecondValue := -1
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else
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SecondValue := taicpu(p_dist).oper[0]^.val;
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{ If both of the TEST constants are identical, delete the
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second TEST that is unnecessary (be careful though, just
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in case the flags are modified in between) }
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if (FirstValue = SecondValue) then
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begin
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{ Since the second jump's condition is a subset of the first, we
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know it will never branch because the first jump dominates it.
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Get it out of the way now rather than wait for the jump
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optimisations for a speed boost. }
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{ We have to check the entire range }
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TempBool := not RegModifiedBetween(NR_DEFAULTFLAGS, hp1, p_dist);
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if condition_in(taicpu(hp1_dist).condition, taicpu(hp1).condition) then
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begin
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{ Since the second jump's condition is a subset of the first, we
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know it will never branch because the first jump dominates it.
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Get it out of the way now rather than wait for the jump
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optimisations for a speed boost. }
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if IsJumpToLabel(taicpu(hp1_dist)) then
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TAsmLabel(taicpu(hp1_dist).oper[0]^.ref^.symbol).DecRefs;
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DebugMsg(SPeepholeOptimization + 'Removed dominated jump (via TEST/Jcc/TEST)', hp1_dist);
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RemoveInstruction(hp1_dist);
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Result := True;
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end
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else if condition_in(inverse_cond(taicpu(hp1).condition), taicpu(hp1_dist).condition) then
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begin
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{ If the inverse of the first condition is a subset of the second,
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the second one will definitely branch if the first one doesn't }
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DebugMsg(SPeepholeOptimization + 'Conditional jump will always branch (via TEST/Jcc/TEST)', hp1_dist);
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{ We can remove the TEST instruction too }
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DebugMsg(SPeepholeOptimization + 'TEST/Jcc/TEST; removed superfluous TEST', p_dist);
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RemoveInstruction(p_dist);
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MakeUnconditional(taicpu(hp1_dist));
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RemoveDeadCodeAfterJump(hp1_dist);
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{ Since the jump is now unconditional, we can't
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continue any further with this particular
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optimisation. The original TEST is still intact
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though, so there might be something else we can
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do }
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Include(OptsToCheck, aoc_ForceNewIteration);
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Break;
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end;
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if Result or
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{ If a jump wasn't removed or made unconditional, only
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remove the identical TEST instruction if the flags
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weren't modified }
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TempBool then
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begin
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DebugMsg(SPeepholeOptimization + 'TEST/Jcc/TEST; removed superfluous TEST', p_dist);
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RemoveInstruction(p_dist);
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{ If the jump was removed or made unconditional, we
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don't need to allocate NR_DEFAULTFLAGS over the
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entire range }
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if not Result then
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begin
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{ Mark the flags as 'in use' over the entire range }
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AllocRegBetween(NR_DEFAULTFLAGS, hp1, hp1_dist, UsedRegs);
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{ Speed gain - continue search from the Jcc instruction }
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hp1_last := hp1_dist;
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{ Only the TEST instruction was removed, and the
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original was unchanged, so we can safely do
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another iteration of the while loop }
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Include(OptsToCheck, aoc_ForceNewIteration);
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Continue;
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end;
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Exit;
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end;
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end;
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if (taicpu(hp1).condition in [C_NE, C_NZ]) and
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(taicpu(hp1_dist).condition in [C_NE, C_NZ]) and
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{ If the first instruction is test %reg,%reg or test $-1,%reg,
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then the second jump will never branch, so it can also be
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removed regardless of where it goes }
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(
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(FirstValue = -1) or
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(SecondValue = -1) or
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MatchOperand(taicpu(hp1_dist).oper[0]^, taicpu(hp1).oper[0]^)
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) then
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begin
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{ Same jump location... can be a register since nothing's changed }
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{ If any of the entries are equivalent to test %reg,%reg, then the
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merged $(x or y) is also test %reg,%reg / test $-1,%reg }
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taicpu(p).loadconst(0, FirstValue or SecondValue);
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if IsJumpToLabel(taicpu(hp1_dist)) then
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TAsmLabel(taicpu(hp1_dist).oper[0]^.ref^.symbol).DecRefs;
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DebugMsg(SPeepholeOptimization + 'Removed dominated jump (via TEST/Jcc/TEST)', hp1_dist);
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DebugMsg(SPeepholeOptimization + 'TEST/JNE/TEST/JNE merged', p);
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RemoveInstruction(hp1_dist);
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end
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else if condition_in(inverse_cond(taicpu(hp1).condition), taicpu(hp1_dist).condition) then
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begin
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{ If the inverse of the first condition is a subset of the second,
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the second one will definitely branch if the first one doesn't }
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DebugMsg(SPeepholeOptimization + 'Conditional jump will always branch (via TEST/Jcc/TEST)', hp1_dist);
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MakeUnconditional(taicpu(hp1_dist));
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RemoveDeadCodeAfterJump(hp1_dist);
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{ Only remove the second test if no jumps or other conditional instructions follow }
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TransferUsedRegs(TmpUsedRegs);
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UpdateUsedRegs(TmpUsedRegs, tai(p.Next));
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UpdateUsedRegs(TmpUsedRegs, tai(hp1.Next));
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if not RegUsedAfterInstruction(NR_DEFAULTFLAGS, p_dist, TmpUsedRegs) then
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RemoveInstruction(p_dist);
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Result := True;
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Exit;
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end;
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Exit;
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end;
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if (taicpu(hp1).condition in [C_NE, C_NZ]) and
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(taicpu(hp1_dist).condition in [C_NE, C_NZ]) and
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{ If the first instruction is test %reg,%reg or test $-1,%reg,
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then the second jump will never branch, so it can also be
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removed regardless of where it goes }
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(
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(FirstValue = -1) or
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(SecondValue = -1) or
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MatchOperand(taicpu(hp1_dist).oper[0]^, taicpu(hp1).oper[0]^)
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) then
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if { If -O2 and under, it may stop on any old instruction }
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(cs_opt_level3 in current_settings.optimizerswitches) and
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(taicpu(p).oper[1]^.typ = top_reg) and
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not RegModifiedByInstruction(taicpu(p).oper[1]^.reg, p_dist) then
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begin
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{ Same jump location... can be a register since nothing's changed }
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{ If any of the entries are equivalent to test %reg,%reg, then the
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merged $(x or y) is also test %reg,%reg / test $-1,%reg }
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taicpu(p).loadconst(0, FirstValue or SecondValue);
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if IsJumpToLabel(taicpu(hp1_dist)) then
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TAsmLabel(taicpu(hp1_dist).oper[0]^.ref^.symbol).DecRefs;
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DebugMsg(SPeepholeOptimization + 'TEST/JNE/TEST/JNE merged', p);
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RemoveInstruction(hp1_dist);
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{ Only remove the second test if no jumps or other conditional instructions follow }
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TransferUsedRegs(TmpUsedRegs);
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UpdateUsedRegs(TmpUsedRegs, tai(p.Next));
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UpdateUsedRegs(TmpUsedRegs, tai(hp1.Next));
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if not RegUsedAfterInstruction(NR_DEFAULTFLAGS, p_dist, TmpUsedRegs) then
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RemoveInstruction(p_dist);
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Result := True;
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Exit;
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hp1_last := p_dist;
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Continue;
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end;
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Break;
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end;
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end;
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@ -6285,8 +6348,6 @@ unit aoptx86;
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function TX86AsmOptimizer.DoMovCmpMemOpt(var p : tai; const hp1: tai) : Boolean;
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var
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hp2: tai;
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begin
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Result := False;
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if MatchOpType(taicpu(p),top_ref,top_reg) and
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@ -6334,13 +6395,8 @@ unit aoptx86;
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RemoveCurrentP(p);
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if (p <> hp1) then
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begin
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{ Correctly update TmpUsedRegs if p and hp1 aren't adjacent }
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hp2 := p;
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repeat
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UpdateUsedRegs(TmpUsedRegs, tai(hp2.Next));
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until not GetNextInstruction(hp2, hp2) or (hp2 = hp1);
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end;
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{ Correctly update TmpUsedRegs if p and hp1 aren't adjacent }
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UpdateUsedRegsBetween(TmpUsedRegs, p, hp1);
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{ Make sure the flags are allocated across the CMP instruction }
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if not RegInUsedRegs(NR_DEFAULTFLAGS, TmpUsedRegs) then
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