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Improve shader BRX instruction code generation (#3759)

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* Improve shader BRX instruction code generation

* Shader cache version bump, add some comments and asserts
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gdkchan 2022-10-15 20:20:16 -03:00 • committed by GitHub
parent e43390c723
commit 2df16ded9b
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5 changed files with 140 additions and 24 deletions
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82
Ryujinx.Graphics.Shader/Instructions/InstEmitFlowControl.cs
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@ -41,24 +41,82 @@ namespace Ryujinx.Graphics.Shader.Instructions
Operand address = context.IAdd(Register(op.SrcA, RegisterType.Gpr), Const(offset));
// Sorting the target addresses in descending order improves the code,
// since it will always check the most distant targets first, then the
// near ones. This can be easily transformed into if/else statements.
var sortedTargets = context.CurrBlock.Successors.Skip(startIndex).OrderByDescending(x => x.Address);
var targets = context.CurrBlock.Successors.Skip(startIndex);
Block lastTarget = sortedTargets.LastOrDefault();
bool allTargetsSinglePred = true;
int total = context.CurrBlock.Successors.Count - startIndex;
int count = 0;
foreach (Block possibleTarget in sortedTargets)
foreach (var target in targets.OrderBy(x => x.Address))
{
Operand label = context.GetLabel(possibleTarget.Address);
if (possibleTarget != lastTarget)
if (++count < total && (target.Predecessors.Count > 1 || target.Address <= context.CurrBlock.Address))
{
context.BranchIfTrue(label, context.ICompareEqual(address, Const((int)possibleTarget.Address)));
allTargetsSinglePred = false;
break;
}
else
}
if (allTargetsSinglePred)
{
// Chain blocks, each target block will check if the BRX target address
// matches its own address, if not, it jumps to the next target which will do the same check,
// until it reaches the last possible target, which executed unconditionally.
// We can only do this if the BRX block is the only predecessor of all target blocks.
// Additionally, this is not supported for blocks located before the current block,
// since it will be too late to insert a label, but this is something that can be improved
// in the future if necessary.
var sortedTargets = targets.OrderBy(x => x.Address);
Block currentTarget = null;
ulong firstTargetAddress = 0;
foreach (Block nextTarget in sortedTargets)
{
context.Branch(label);
if (currentTarget != null)
{
if (currentTarget.Address != nextTarget.Address)
{
context.SetBrxTarget(currentTarget.Address, address, (int)currentTarget.Address, nextTarget.Address);
}
}
else
{
firstTargetAddress = nextTarget.Address;
}
currentTarget = nextTarget;
}
context.Branch(context.GetLabel(firstTargetAddress));
}
else
{
// Emit the branches sequentially.
// This generates slightly worse code, but should work for all cases.
var sortedTargets = targets.OrderByDescending(x => x.Address);
ulong lastTargetAddress = ulong.MaxValue;
count = 0;
foreach (Block target in sortedTargets)
{
Operand label = context.GetLabel(target.Address);
if (++count < total)
{
if (target.Address != lastTargetAddress)
{
context.BranchIfTrue(label, context.ICompareEqual(address, Const((int)target.Address)));
}
lastTargetAddress = target.Address;
}
else
{
context.Branch(label);
}
}
}
}