From 8d557d4103507ed1e3f408449ee6b83638827bde Mon Sep 17 00:00:00 2001 From: Hans-Kristian Arntzen Date: Thu, 8 Mar 2018 14:01:10 +0100 Subject: [PATCH] Handle cases where merge selects as also loop merge or continue blocks. --- spirv_cross.hpp | 5 ++ spirv_glsl.cpp | 150 +++++++++++++++++++++++++++++------------------- spirv_glsl.hpp | 1 + 3 files changed, 98 insertions(+), 58 deletions(-) diff --git a/spirv_cross.hpp b/spirv_cross.hpp index 714a067..ef0776b 100644 --- a/spirv_cross.hpp +++ b/spirv_cross.hpp @@ -585,6 +585,11 @@ protected: multiselect_merge_targets.find(next) != end(multiselect_merge_targets); } + inline bool is_loop_break(uint32_t next) const + { + return loop_merge_targets.find(next) != end(loop_merge_targets); + } + inline bool is_conditional(uint32_t next) const { return selection_merge_targets.find(next) != end(selection_merge_targets) && diff --git a/spirv_glsl.cpp b/spirv_glsl.cpp index 2abd99d..5fb4cea 100644 --- a/spirv_glsl.cpp +++ b/spirv_glsl.cpp @@ -8316,6 +8316,63 @@ void CompilerGLSL::flush_phi(uint32_t from, uint32_t to) } } +void CompilerGLSL::branch_to_continue(uint32_t from, uint32_t to) +{ + assert(is_continue(to)); + + auto &to_block = get(to); + if (to_block.complex_continue) + { + // Just emit the whole block chain as is. + auto usage_counts = expression_usage_counts; + auto invalid = invalid_expressions; + + emit_block_chain(to_block); + + // Expression usage counts and invalid expressions + // are moot after returning from the continue block. + // Since we emit the same block multiple times, + // we don't want to invalidate ourselves. + expression_usage_counts = usage_counts; + invalid_expressions = invalid; + } + else + { + auto &from_block = get(from); + bool outside_control_flow = false; + uint32_t loop_dominator = 0; + + // FIXME: Refactor this to not use the old loop_dominator tracking. + if (from_block.merge_block) + { + // If we are a loop header, we don't set the loop dominator, + // so just use "self" here. + loop_dominator = from; + } + else if (from_block.loop_dominator != SPIRBlock::NoDominator) + { + loop_dominator = from_block.loop_dominator; + } + + if (loop_dominator != 0) + { + auto &dominator = get(loop_dominator); + + // For non-complex continue blocks, we implicitly branch to the continue block + // by having the continue block be part of the loop header in for (; ; continue-block). + outside_control_flow = block_is_outside_flow_control_from_block(dominator, from_block); + } + + // Some simplification for for-loops. We always end up with a useless continue; + // statement since we branch to a loop block. + // Walk the CFG, if we uncoditionally execute the block calling continue assuming we're in the loop block, + // we can avoid writing out an explicit continue statement. + // Similar optimization to return statements if we know we're outside flow control. + if (!outside_control_flow) + statement("continue;"); + } +} + void CompilerGLSL::branch(uint32_t from, uint32_t to) { flush_phi(from, to); @@ -8329,64 +8386,17 @@ void CompilerGLSL::branch(uint32_t from, uint32_t to) // and end the chain here. statement("continue;"); } - else if (is_continue(to)) - { - auto &to_block = get(to); - if (to_block.complex_continue) - { - // Just emit the whole block chain as is. - auto usage_counts = expression_usage_counts; - auto invalid = invalid_expressions; - - emit_block_chain(to_block); - - // Expression usage counts and invalid expressions - // are moot after returning from the continue block. - // Since we emit the same block multiple times, - // we don't want to invalidate ourselves. - expression_usage_counts = usage_counts; - invalid_expressions = invalid; - } - else - { - auto &from_block = get(from); - bool outside_control_flow = false; - uint32_t loop_dominator = 0; - - // FIXME: Refactor this to not use the old loop_dominator tracking. - if (from_block.merge_block) - { - // If we are a loop header, we don't set the loop dominator, - // so just use "self" here. - loop_dominator = from; - } - else if (from_block.loop_dominator != SPIRBlock::NoDominator) - { - loop_dominator = from_block.loop_dominator; - } - - if (loop_dominator != 0) - { - auto &dominator = get(loop_dominator); - - // For non-complex continue blocks, we implicitly branch to the continue block - // by having the continue block be part of the loop header in for (; ; continue-block). - outside_control_flow = block_is_outside_flow_control_from_block(dominator, from_block); - } - - // Some simplification for for-loops. We always end up with a useless continue; - // statement since we branch to a loop block. - // Walk the CFG, if we uncoditionally execute the block calling continue assuming we're in the loop block, - // we can avoid writing out an explicit continue statement. - // Similar optimization to return statements if we know we're outside flow control. - if (!outside_control_flow) - statement("continue;"); - } - } else if (is_break(to)) statement("break;"); + else if (is_continue(to)) + branch_to_continue(from, to); else if (!is_conditional(to)) emit_block_chain(get(to)); + + // It is important that we check for break before continue. + // A block might serve two purposes, a break block for the inner scope, and + // a continue block in the outer scope. + // Inner scope always takes precedence. } void CompilerGLSL::branch(uint32_t from, uint32_t cond, uint32_t true_block, uint32_t false_block) @@ -8395,6 +8405,9 @@ void CompilerGLSL::branch(uint32_t from, uint32_t cond, uint32_t true_block, uin bool true_sub = !is_conditional(true_block); bool false_sub = !is_conditional(false_block); + // It is possible that a selection merge target also serves as a break/continue block. + // We will not emit break or continue here, but defer that to the outer scope. + if (true_sub) { statement("if (", to_expression(cond), ")"); @@ -8420,7 +8433,7 @@ void CompilerGLSL::branch(uint32_t from, uint32_t cond, uint32_t true_block, uin else if (false_sub && !true_sub) { // Only need false path, use negative conditional. - statement("if (!", to_expression(cond), ")"); + statement("if (!", to_enclosed_expression(cond), ")"); begin_scope(); branch(from, false_block); end_scope(); @@ -8959,7 +8972,23 @@ void CompilerGLSL::emit_block_chain(SPIRBlock &block) // that block after this. If we had selection merge, we already flushed phi variables. if (block.merge != SPIRBlock::MergeSelection) flush_phi(block.self, block.next_block); - emit_block_chain(get(block.next_block)); + + // For merge selects we might have ignored the fact that a merge target + // could have been a break; or continue; + // We will need to deal with it here. + if (is_loop_break(block.next_block)) + { + // Cannot check for just break, because switch statements will also use break. + assert(block.merge == SPIRBlock::MergeSelection); + statement("break;"); + } + else if (is_continue(block.next_block)) + { + assert(block.merge == SPIRBlock::MergeSelection); + branch_to_continue(block.self, block.next_block); + } + else + emit_block_chain(get(block.next_block)); } if (block.merge == SPIRBlock::MergeLoop) @@ -8982,8 +9011,13 @@ void CompilerGLSL::emit_block_chain(SPIRBlock &block) else end_scope(); - flush_phi(block.self, block.merge_block); - emit_block_chain(get(block.merge_block)); + // We cannot break out of two loops at once, so don't check for break; here. + // Using block.self as the "from" block isn't quite right, but it has the same scope + // and dominance structure, so it's fine. + if (is_continue(block.merge_block)) + branch_to_continue(block.self, block.merge_block); + else + emit_block_chain(get(block.merge_block)); } } diff --git a/spirv_glsl.hpp b/spirv_glsl.hpp index db870b7..d04654c 100644 --- a/spirv_glsl.hpp +++ b/spirv_glsl.hpp @@ -356,6 +356,7 @@ protected: void propagate_loop_dominators(const SPIRBlock &block); void branch(uint32_t from, uint32_t to); + void branch_to_continue(uint32_t from, uint32_t to); void branch(uint32_t from, uint32_t cond, uint32_t true_block, uint32_t false_block); void flush_phi(uint32_t from, uint32_t to); bool flush_phi_required(uint32_t from, uint32_t to);