From 2df16ded9ba06a874b58132cc2c78175631a3b8d Mon Sep 17 00:00:00 2001
From: gdkchan <gab.dark.100@gmail.com>
Date: Sat, 15 Oct 2022 20:20:16 -0300
Subject: Improve shader BRX instruction code generation (#3759)
* Improve shader BRX instruction code generation
* Shader cache version bump, add some comments and asserts
---
.../Instructions/InstEmitFlowControl.cs | 80 +++++++++++++++++++---
1 file changed, 69 insertions(+), 11 deletions(-)
(limited to 'Ryujinx.Graphics.Shader/Instructions/InstEmitFlowControl.cs')
diff --git a/Ryujinx.Graphics.Shader/Instructions/InstEmitFlowControl.cs b/Ryujinx.Graphics.Shader/Instructions/InstEmitFlowControl.cs
index aee52c51..f1dd279c 100644
--- a/Ryujinx.Graphics.Shader/Instructions/InstEmitFlowControl.cs
+++ b/Ryujinx.Graphics.Shader/Instructions/InstEmitFlowControl.cs
@@ -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 (++count < total && (target.Predecessors.Count > 1 || target.Address <= context.CurrBlock.Address))
+ {
+ allTargetsSinglePred = false;
+ break;
+ }
+ }
+
+ 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);
- if (possibleTarget != lastTarget)
+ Block currentTarget = null;
+ ulong firstTargetAddress = 0;
+
+ foreach (Block nextTarget in sortedTargets)
{
- context.BranchIfTrue(label, context.ICompareEqual(address, Const((int)possibleTarget.Address)));
+ if (currentTarget != null)
+ {
+ if (currentTarget.Address != nextTarget.Address)
+ {
+ context.SetBrxTarget(currentTarget.Address, address, (int)currentTarget.Address, nextTarget.Address);
+ }
+ }
+ else
+ {
+ firstTargetAddress = nextTarget.Address;
+ }
+
+ currentTarget = nextTarget;
}
- else
+
+ 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)
{
- context.Branch(label);
+ 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);
+ }
}
}
}
--
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