[PATCH] RISC-V: improve codegen for large constants with same 32-bit lo and hi parts [2]

[PATCH] RISC-V: improve codegen for large constants with same 32-bit lo and hi parts [2]

[Vineet Gupta]

[part #2 of PR/109279]

SPEC2017 deepsjeng uses large constants which currently generates less than
ideal code. This fix improves codegen for large constants which have
same low and hi parts: e.g.

	long long f(void) { return 0x0101010101010101ull; }

Before
        li      a5,0x1010000
        addi    a5,a5,0x101
        mv      a0,a5
        slli    a5,a5,32
        add     a0,a5,a0
        ret

With patch
	li	a5,0x1010000
	addi	a5,a5,0x101
	slli	a0,a5,32
	add	a0,a0,a5
	ret

This is testsuite clean.

gcc/ChangeLog:

	* config/riscv/riscv.cc (riscv_split_integer): if loval is equal
	  to hival, ASHIFT the corresponding regs.

Signed-off-by: Vineet Gupta <vineetg@rivosinc.com>
---
 gcc/config/riscv/riscv.cc | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 79122699b6f5..4e1bb2f14cf8 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -703,13 +703,18 @@ riscv_split_integer (HOST_WIDE_INT val, machine_mode mode)
   unsigned HOST_WIDE_INT hival = sext_hwi ((val - loval) >> 32, 32);
   rtx hi = gen_reg_rtx (mode), lo = gen_reg_rtx (mode);
 
-  riscv_move_integer (hi, hi, hival, mode);
   riscv_move_integer (lo, lo, loval, mode);
 
-  hi = gen_rtx_fmt_ee (ASHIFT, mode, hi, GEN_INT (32));
-  hi = force_reg (mode, hi);
+  if (loval == hival)
+      hi = gen_rtx_ASHIFT (mode, lo, GEN_INT (32));
+  else
+    {
+      riscv_move_integer (hi, hi, hival, mode);
+      hi = gen_rtx_ASHIFT (mode, hi, GEN_INT (32));
+    }
 
-  return gen_rtx_fmt_ee (PLUS, mode, hi, lo);
+  hi = force_reg (mode, hi);
+  return gen_rtx_PLUS (mode, hi, lo);
 }
 
 /* Return true if X is a thread-local symbol.  */
-- 
2.34.1

Re: [PATCH] RISC-V: improve codegen for large constants with same 32-bit lo and hi parts [2]

[Jeff Law]

On 5/18/23 14:57, Vineet Gupta wrote:
> [part #2 of PR/109279]
> 
> SPEC2017 deepsjeng uses large constants which currently generates less than
> ideal code. This fix improves codegen for large constants which have
> same low and hi parts: e.g.
> 
> 	long long f(void) { return 0x0101010101010101ull; }
> 
> Before
>          li      a5,0x1010000
>          addi    a5,a5,0x101
>          mv      a0,a5
>          slli    a5,a5,32
>          add     a0,a5,a0
>          ret
> 
> With patch
> 	li	a5,0x1010000
> 	addi	a5,a5,0x101
> 	slli	a0,a5,32
> 	add	a0,a0,a5
> 	ret
> 
> This is testsuite clean.
> 
> gcc/ChangeLog:
> 
> 	* config/riscv/riscv.cc (riscv_split_integer): if loval is equal
> 	  to hival, ASHIFT the corresponding regs.
LGTM.  Please install.  Thanks for taking care of this!  The updated 
sequence looks good.

Jeff

Re: [PATCH] RISC-V: improve codegen for large constants with same 32-bit lo and hi parts [2]

[Palmer Dabbelt]

On Fri, 19 May 2023 09:33:34 PDT (-0700), jeffreyalaw@gmail.com wrote:
>
>
> On 5/18/23 14:57, Vineet Gupta wrote:
>> [part #2 of PR/109279]
>>
>> SPEC2017 deepsjeng uses large constants which currently generates less than
>> ideal code. This fix improves codegen for large constants which have
>> same low and hi parts: e.g.
>>
>> 	long long f(void) { return 0x0101010101010101ull; }
>>
>> Before
>>          li      a5,0x1010000
>>          addi    a5,a5,0x101
>>          mv      a0,a5
>>          slli    a5,a5,32
>>          add     a0,a5,a0
>>          ret
>>
>> With patch
>> 	li	a5,0x1010000
>> 	addi	a5,a5,0x101
>> 	slli	a0,a5,32
>> 	add	a0,a0,a5
>> 	ret
>>
>> This is testsuite clean.
>>
>> gcc/ChangeLog:
>>
>> 	* config/riscv/riscv.cc (riscv_split_integer): if loval is equal
>> 	  to hival, ASHIFT the corresponding regs.
> LGTM.  Please install.  Thanks for taking care of this!  The updated
> sequence looks good.

Works for me.  Did you start that performance backports branch?  Either 
way, I think this should go on it.

Re: [PATCH] RISC-V: improve codegen for large constants with same 32-bit lo and hi parts [2]

[Vineet Gupta]

On 5/19/23 09:36, Palmer Dabbelt wrote:
> Works for me.  Did you start that performance backports branch?  
> Either way, I think this should go on it. 

Please note that there is a bit of dependency chain. Assuming the 
aforementioned branch is gcc 13.1 based, this change also needs my 
splitter relaxation fix g0530254413f8 to ensure incremental improvements 
to large const codegen.

[Committed] RISC-V: improve codegen for large constants with same 32-bit lo and hi parts [2]

[Vineet Gupta]

On 5/19/23 09:33, Jeff Law wrote:
>
>
> On 5/18/23 14:57, Vineet Gupta wrote:
>> [part #2 of PR/109279]
>>
>> SPEC2017 deepsjeng uses large constants which currently generates 
>> less than
>> ideal code. This fix improves codegen for large constants which have
>> same low and hi parts: e.g.
>>
>>     long long f(void) { return 0x0101010101010101ull; }
>>
>> Before
>>          li      a5,0x1010000
>>          addi    a5,a5,0x101
>>          mv      a0,a5
>>          slli    a5,a5,32
>>          add     a0,a5,a0
>>          ret
>>
>> With patch
>>     li    a5,0x1010000
>>     addi    a5,a5,0x101
>>     slli    a0,a5,32
>>     add    a0,a0,a5
>>     ret
>>
>> This is testsuite clean.
>>
>> gcc/ChangeLog:
>>
>>     * config/riscv/riscv.cc (riscv_split_integer): if loval is equal
>>       to hival, ASHIFT the corresponding regs.
> LGTM.  Please install.  Thanks for taking care of this!  The updated 
> sequence looks good.
>
> Jeff