From 32b6c63485626f10b3bc8efb0239064cc781115e Mon Sep 17 00:00:00 2001
From: ReinUsesLisp <reinuseslisp@airmail.cc>
Date: Wed, 17 Mar 2021 01:33:25 -0300
Subject: shader: Reorder phi nodes when redefined as undefined opcodes
---
src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
(limited to 'src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp')
diff --git a/src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp b/src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp
index f89fd51c8a..d09bcec366 100644
--- a/src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp
+++ b/src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp
@@ -181,8 +181,16 @@ private:
}
if (same.IsEmpty()) {
// The phi is unreachable or in the start block
- const auto first_not_phi{std::ranges::find_if_not(block->Instructions(), IsPhi)};
+ // First remove the phi node from the block, it will be reinserted
+ IR::Block::InstructionList& list{block->Instructions()};
+ list.erase(IR::Block::InstructionList::s_iterator_to(phi));
+
+ // Insert an undef instruction after all phi nodes (to keep phi instructions on top)
+ const auto first_not_phi{std::ranges::find_if_not(list, IsPhi)};
same = IR::Value{&*block->PrependNewInst(first_not_phi, undef_opcode)};
+
+ // Insert the phi node after the undef opcode, this will be replaced with an identity
+ list.insert(first_not_phi, phi);
}
// Reroute all uses of phi to same and remove phi
phi.ReplaceUsesWith(same);
--
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