Hi,
On 26 August 2017 at 18:10, Pinski, Andrew Andrew.Pinski@cavium.com wrote:
However there might be pushback from upstream maintainers as this makes the structure bigger by adding a field. This could have implications for memory usage of the compiler.
I looked into the structure, adding this field is not going to make the structure bigger for either ILP32 or LP64 targets. If you want, you use bit-fields; there is one bool already there which means you can fit 8 bits in the same area as currently taken up by that one.
Yes. I should have checked the mem_attrs structure. This does have at least a byte left unlike some other tightly packed structures (gimple and some tree structures in gcc).
Thanks, Kugan
Alternatively, we maybe able to get this info from dwarf info when we compile with -g ?
I doubt you can. He wants to know if an instruction is a spill location. The location of a variable might be recorded in -g (if it was an user variable) but not that does present the data for all temps being spilled.
I think the patch is actually a good one in general just needs some cleanup.
As for these comments:
For example, GCC calls `output_asm_insn' directly from the `define_insn' definition in the aarch64.md file without an insn object(`output_asm_insn' calls `output_asm_operand_names'). This occurs in "*cb<optab><mode>1" and "*aarch64_fcvt<su_optab>GPF:modeGPI:mode2_mult".
Spills in GCC will always be via the mov* patterns (they are special). Now really *aarch64_fcvt<su_optab>GPF:modeGPI:mode2_mult should be fixed for a different reason; it does unneeded work. The fix would be something like (untested): { operands[2] = GEN_INT (aarch64_fpconst_pow_of_2 (operands[2])); return "fcvtz<su>\t%GPI:w0, %GPF:s1, %2"; }
Thanks, Andrew
-----Original Message----- From: linaro-toolchain [mailto:linaro-toolchain-bounces@lists.linaro.org] On Behalf Of Kugan Vivekanandarajah Sent: Saturday, August 26, 2017 12:40 AM To: Renato Golin renato.golin@linaro.org Cc: Jim Wilson jim.wilson@linaro.org; hpc-sig-devel@linaro.org; Linaro Toolchain linaro-toolchain@lists.linaro.org Subject: Re: [hpc-sig-devel] GCC extensions for `hcqc'
Hi,
On 26 August 2017 at 04:04, Renato Golin renato.golin@linaro.org wrote:
+linaro-toolchain, hoping to get more eyes into it.
cheers, --renato
On 25 August 2017 at 17:59, Masaki Arai masaki.arai@linaro.org wrote:
Hi,
I extended GCC 7.1(or GCC 7.2) for `hcqc'. I would be grateful if you could give me a comment about whether this extension is acceptable and whether this extension should be pushed upstream.
I think this is a useful info. However there might be pushback from upstream maintainers as this makes the structure bigger by adding a field. This could have implications for memory usage of the compiler. Alternatively, we maybe able to get this info from dwarf info when we compile with -g ? Jim may have some input here (cc ing him).
Thanks, Kugan
The extended GCC's output using the option ` -fverbose-asm' is as follows:
ldr w0, [x29,48] // tmp433, j(8-byte Folded Spill) ^^^^^^^^^^^^^^^^^^^ This code shows that this instruction accesses a memory area for spill codes. I made the following changes to GCC 7.1(or GCC 7.2). The related files are under `hcqc/patch/gcc-7.1.0-add'.
(1) rtl.h
I added flag information to `struct mem_attrs' that means whether it is a spill memory area or not.
- /* True if the MEM is for spill. */
- bool for_spill_p;
Also, I added an access macro for this additional field.
- /* For a MEM rtx, true if its MEM is for spill. */ #define
- MEM_FOR_SPILL_P(RTX) (get_mem_attrs (RTX)->for_spill_p)
(2) emit-rtl.c
I added a code to turn on flags for spill memory area in function `set_mem_attrs_for_spill'.
- attrs.for_spill_p = true;
(3) final.c
I added code to print that information in function `output_asm_operand_names' if the memory is a spill memory area,
if (MEM_P (op) && MEM_FOR_SPILL_P (op)){HOST_WIDE_INT size = MEM_SIZE (op);fprintf (asm_out_file, " (" HOST_WIDE_INT_PRINT_DEC "-byte- Folded
Spill)", size);
}The above changes are implemented similarly as Clang/LLVM. Unfortunately, it is difficult for GCC to print the above "(?-byte Folded Spill)" for memory access instructions only in the same manner as Clang/LLVM. The reason is that GCC executes the above `output_asm_operand_names' even in situations where any instruction object(insn) does not exist when outputting assembly code. For example, GCC calls `output_asm_insn' directly from the `define_insn' definition in the aarch64.md file without an insn object(`output_asm_insn' calls `output_asm_operand_names'). This occurs in "*cb<optab><mode>1" and "*aarch64_fcvt<su_optab>GPF:modeGPI:mode2_mult".
From this fact, `hcqc' extracts and accumulates memory access instructions from the assembly code with the comment "(?-byte Folded Spill)".
The above extensions are commonly available on almost any architecture. Also, these extensions do not affect the execution of the resulting assembly code since additional outputs are only in comments.
Best regards,
Masaki Arai
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