Reduce superfluous move instructions #32
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This commit reduces superfluous move instructions in the object code (at least for x86_64) by changing internal representation of HSA registers in gccbrig. Instead representing HSA's untyped registers as unsigned int the gccbrig analyzes brig code and builds the register variables as a type used in tree expressions at most. This gives better chance to optimize CONVERT_VIEW_EXPRs away.
| else | ||
| element = convert (operand_type, element); | ||
| } | ||
| element = build_reinterpret_cast (operand_type, element); |
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Is this correct? Don't we need proper casting (via the convert call) when the integer sizes differ to ensure no garbage is left to the upper bits?
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I changed build_reinterpret_cast to do unsigned convert (zero extend or clip out upper bits when sizes differ). Signedness does not seem to matter here in the tests I have run but I check couple more cases for this.
| @@ -1141,6 +1138,23 @@ brig_code_entry_handler::build_h2f_conversion (tree source) | |||
| tree_stl_vec | |||
| brig_code_entry_handler::build_operands (const BrigInstBase &brig_inst) | |||
| { | |||
| return build_or_analyze_operands (brig_inst, /* analyze = */ false); | |||
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Please drop the comment, why it's there? Also below?
| } | ||
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| /* Implements both the build_operands () and analyze_operands () call | ||
| so changes goes in tandem. Performs build_operands () when ANALYZE |
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Also briefly explain what is being analyzed.
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| /* Implements both the build_operands () and analyze_operands () call | ||
| so changes goes in tandem. Performs build_operands () when ANALYZE | ||
| is false. Otherwise, analyze operands and return empty list. */ |
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-> "only analyze the operands and return an empty list."
| operand = build_reinterpret_cast (operand_type, operand); | ||
| else if (reg_width > instr_width) | ||
| { | ||
| /* Clip the operand because the instruction's bitwidth |
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Again, is this really safe to replace with an interpret cast?
gcc/brig/brigfrontend/brig-util.cc
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| for (regs_use_index::const_iterator it = begin_it; it != end_it; it++) | ||
| { | ||
| std::string hsa_reg = gccbrig_hsa_reg_name_from_hash (it->first); | ||
| printf ("%s:\n", hsa_reg.c_str ()); |
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Is it correct to always output to 'stdout' with the verbose output, or is there some stream variable for it in GCC?
gcc/brig/brigfrontend/brig-util.h
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| @@ -76,4 +86,25 @@ bool gccbrig_might_be_host_defined_var_p (const BrigDirectiveVariable *brigVar); | |||
| /* From hsa.h. */ | |||
| bool hsa_type_packed_p (BrigType16_t type); | |||
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| struct reg_use_info | |||
| { | |||
| /* The generic tree types as the registers is interpreted and their | |||
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This comment is a bit unclear. Also GCC style requires two spaces after dots.
Something like this would be clearer:
"This vector keeps count of the times an HSAIL register is used for storing data of a given type..."
| /* Test for casting from/to representation of HSA registers. */ | ||
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| /* HSA registers are untyped but in gccbrig they are presented as */ | ||
| /* variables with a type selected by analysis. Currently, each */ |
| /* HSA registers are untyped but in gccbrig they are presented as */ | ||
| /* variables with a type selected by analysis. Currently, each */ | ||
| /* register variable, per function, has a type as it is used at */ | ||
| /* most. Therefore, register variable can be nearly any type. The */ |
| { | ||
| private_u64 %foo; | ||
| private_u64 %bar; | ||
| private_b128 %baz; |
* Style fixes. * Remove reg use info printing. * Rename build_reinterpret_cast to build_resize_convert_view to reflect the new semantics better.
This commit reduces superfluous move instructions in the object code
(at least for x86_64) by changing internal representation of HSA
registers in gccbrig. Instead representing HSA's untyped registers as
unsigned int the gccbrig analyzes brig code and builds the register
variables as a type used in tree expressions at most. This gives
better chance to optimize CONVERT_VIEW_EXPRs away.