Skip line directives when emitting loop condition blocks.

Avoids problem where enabling line directives breaks loop optimizations
since it thinks there are legitimate statements in the block.

2 files changed, 20 insertions, 2 deletions

diff --git a/spirv_glsl.cpp b/spirv_glsl.cpp
index f2104ff8..d7ee9356 100644
--- a/spirv_glsl.cpp
+++ b/spirv_glsl.cpp
@@ -16426,6 +16426,17 @@ bool CompilerGLSL::for_loop_initializers_are_same_type(const SPIRBlock &block)
 	return true;
 }
 
+void CompilerGLSL::emit_block_instructions_with_masked_debug(SPIRBlock &block)
+{
+	// Have to block debug instructions such as OpLine here, since it will be treated as a statement otherwise,
+	// which breaks loop optimizations.
+	// Any line directive would be declared outside the loop body, which would just be confusing either way.
+	bool old_block_debug_directives = block_debug_directives;
+	block_debug_directives = true;
+	emit_block_instructions(block);
+	block_debug_directives = old_block_debug_directives;
+}
+
 bool CompilerGLSL::attempt_emit_loop_header(SPIRBlock &block, SPIRBlock::Method method)
 {
 	SPIRBlock::ContinueBlockType continue_type = continue_block_type(get<SPIRBlock>(block.continue_block));
@@ -16436,7 +16447,7 @@ bool CompilerGLSL::attempt_emit_loop_header(SPIRBlock &block, SPIRBlock::Method
 		// If we're trying to create a true for loop,
 		// we need to make sure that all opcodes before branch statement do not actually emit any code.
 		// We can then take the condition expression and create a for (; cond ; ) { body; } structure instead.
-		emit_block_instructions(block);
+		emit_block_instructions_with_masked_debug(block);
 
 		bool condition_is_temporary = forced_temporaries.find(block.condition) == end(forced_temporaries);
 
@@ -16516,7 +16527,7 @@ bool CompilerGLSL::attempt_emit_loop_header(SPIRBlock &block, SPIRBlock::Method
 		// If we're trying to create a true for loop,
 		// we need to make sure that all opcodes before branch statement do not actually emit any code.
 		// We can then take the condition expression and create a for (; cond ; ) { body; } structure instead.
-		emit_block_instructions(child);
+		emit_block_instructions_with_masked_debug(child);
 
 		bool condition_is_temporary = forced_temporaries.find(child.condition) == end(forced_temporaries);
 
@@ -17895,6 +17906,11 @@ void CompilerGLSL::emit_line_directive(uint32_t file_id, uint32_t line_literal)
 	if (redirect_statement)
 		return;
 
+	// If we're emitting code in a sensitive context such as condition blocks in for loops, don't emit
+	// any line directives, because it's not possible.
+	if (block_debug_directives)
+		return;
+
 	if (options.emit_line_directives)
 	{
 		require_extension_internal("GL_GOOGLE_cpp_style_line_directive");
diff --git a/spirv_glsl.hpp b/spirv_glsl.hpp
index 66b23cbe..8a841f34 100644
--- a/spirv_glsl.hpp
+++ b/spirv_glsl.hpp
@@ -397,6 +397,7 @@ protected:
 	};
 	TemporaryCopy handle_instruction_precision(const Instruction &instr);
 	void emit_block_instructions(SPIRBlock &block);
+	void emit_block_instructions_with_masked_debug(SPIRBlock &block);
 
 	// For relax_nan_checks.
 	GLSLstd450 get_remapped_glsl_op(GLSLstd450 std450_op) const;
@@ -545,6 +546,7 @@ protected:
 	SmallVector<std::string> *redirect_statement = nullptr;
 	const SPIRBlock *current_continue_block = nullptr;
 	bool block_temporary_hoisting = false;
+	bool block_debug_directives = false;
 
 	void begin_scope();
 	void end_scope();