[MSP430,3/4] Disable performance optimal library code shifts when optimizing for size

Message ID 20190604141421.40fdd98d@jozef-kubuntu
State New
Headers show
Series
  • Reduce code size when performing bit shifts
Related show

Commit Message

Jozef Lawrynowicz June 4, 2019, 1:14 p.m.
This patch reduces code size by disabling the performance optimized,
"const_variant" of shift library functions when optimization for size is
enabled.

For the following program, the below code size reduction is observed:
  long a;

  int
  main (void)
  {
    a = a >> 4;
    return 0;
  }

With shift patch 2:
   text    data     bss     dec     hex filename
    522      12      22     556     22c a.out
New patch:
   text    data     bss     dec     hex filename
    474      12      22     508     1fc a.out

Ok for trunk?

Comments

Jeff Law June 5, 2019, 10:22 p.m. | #1
On 6/4/19 7:14 AM, Jozef Lawrynowicz wrote:
> This patch reduces code size by disabling the performance optimized,

> "const_variant" of shift library functions when optimization for size is

> enabled.

> 

> For the following program, the below code size reduction is observed:

>   long a;

> 

>   int

>   main (void)

>   {

>     a = a >> 4;

>     return 0;

>   }

> 

> With shift patch 2:

>    text    data     bss     dec     hex filename

>     522      12      22     556     22c a.out

> New patch:

>    text    data     bss     dec     hex filename

>     474      12      22     508     1fc a.out

> 

> Ok for trunk?

> 

> 

> 0003-MSP430-Do-not-use-the-performance-optimized-variant-.patch

> 

> From 894b6809822ba3a3a1bab3750abe29e03f2a3ad6 Mon Sep 17 00:00:00 2001

> From: Jozef Lawrynowicz <jozef.l@mittosystems.com>

> Date: Mon, 13 May 2019 17:52:19 +0100

> Subject: [PATCH 3/4] MSP430: Do not use the performance optimized variant of a

>  shift by constant amount when optimizing for size

> 

> gcc/ChangeLog

> 

> 2019-06-04  Jozef Lawrynowicz  <jozef.l@mittosystems.com>

> 

> 	* config/msp430/msp430.md (ashlhi3): Use the const_variant of shift

> 	library functions only when not optimizing for size.

> 	(ashlsi3): Likewise.

> 	(ashrhi3): Likewise.

> 	(ashrsi3): Likewise.

> 	(lshrhi3): Likewise.

> 	(lshrsi3): Likewise.

> 

> gcc/testsuite/ChangeLog

> 

> 2019-06-04  Jozef Lawrynowicz  <jozef.l@mittosystems.com>

> 

> 	* gcc.target/msp430/size-optimized-shifts.c: New test.

OK
jeff

Patch

From 894b6809822ba3a3a1bab3750abe29e03f2a3ad6 Mon Sep 17 00:00:00 2001
From: Jozef Lawrynowicz <jozef.l@mittosystems.com>
Date: Mon, 13 May 2019 17:52:19 +0100
Subject: [PATCH 3/4] MSP430: Do not use the performance optimized variant of a
 shift by constant amount when optimizing for size

gcc/ChangeLog

2019-06-04  Jozef Lawrynowicz  <jozef.l@mittosystems.com>

	* config/msp430/msp430.md (ashlhi3): Use the const_variant of shift
	library functions only when not optimizing for size.
	(ashlsi3): Likewise.
	(ashrhi3): Likewise.
	(ashrsi3): Likewise.
	(lshrhi3): Likewise.
	(lshrsi3): Likewise.

gcc/testsuite/ChangeLog

2019-06-04  Jozef Lawrynowicz  <jozef.l@mittosystems.com>

	* gcc.target/msp430/size-optimized-shifts.c: New test.
---
 gcc/config/msp430/msp430.md                   | 15 ++++++-----
 .../gcc.target/msp430/size-optimized-shifts.c | 26 +++++++++++++++++++
 2 files changed, 35 insertions(+), 6 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/msp430/size-optimized-shifts.c

diff --git a/gcc/config/msp430/msp430.md b/gcc/config/msp430/msp430.md
index 58c1f4edc9c..76296a2f317 100644
--- a/gcc/config/msp430/msp430.md
+++ b/gcc/config/msp430/msp430.md
@@ -769,7 +769,10 @@ 
 	     && INTVAL (operands[2]) == 1)
       emit_insn (gen_slli_1 (operands[0], operands[1]));
     else		 
-      msp430_expand_helper (operands, \"__mspabi_slli\", true);
+      /* The const variants of mspabi shifts have larger code size than the
+	 generic version, so use the generic version if optimizing for
+	 size.  */
+      msp430_expand_helper (operands, \"__mspabi_slli\", !optimize_size);
     DONE;
   }
 )
@@ -815,7 +818,7 @@ 
 	(ashift:SI (match_operand:SI 1 "general_operand")
 		   (match_operand:SI 2 "general_operand")))]
   ""
-  "msp430_expand_helper (operands, \"__mspabi_slll\", true);
+  "msp430_expand_helper (operands, \"__mspabi_slll\", !optimize_size);
    DONE;"
 )
 
@@ -842,7 +845,7 @@ 
 	     && INTVAL (operands[2]) == 1)
       emit_insn (gen_srai_1 (operands[0], operands[1]));
     else		 
-       msp430_expand_helper (operands, \"__mspabi_srai\", true);
+       msp430_expand_helper (operands, \"__mspabi_srai\", !optimize_size);
    DONE;
    }
 )
@@ -904,7 +907,7 @@ 
 	(ashiftrt:SI (match_operand:SI 1 "general_operand")
 		     (match_operand:SI 2 "general_operand")))]
   ""
-  "msp430_expand_helper (operands, \"__mspabi_sral\", true);
+  "msp430_expand_helper (operands, \"__mspabi_sral\", !optimize_size);
    DONE;"
 )
 
@@ -931,7 +934,7 @@ 
 	     && INTVAL (operands[2]) == 1)
       emit_insn (gen_srli_1 (operands[0], operands[1]));
     else		 
-      msp430_expand_helper (operands, \"__mspabi_srli\", true);
+      msp430_expand_helper (operands, \"__mspabi_srli\", !optimize_size);
     DONE;
   }
 )
@@ -983,7 +986,7 @@ 
 	(lshiftrt:SI (match_operand:SI 1 "general_operand")
 		     (match_operand:SI 2 "general_operand")))]
   ""
-  "msp430_expand_helper (operands, \"__mspabi_srll\", true);
+  "msp430_expand_helper (operands, \"__mspabi_srll\", !optimize_size);
    DONE;"
 )
 
diff --git a/gcc/testsuite/gcc.target/msp430/size-optimized-shifts.c b/gcc/testsuite/gcc.target/msp430/size-optimized-shifts.c
new file mode 100644
index 00000000000..be9509b86cc
--- /dev/null
+++ b/gcc/testsuite/gcc.target/msp430/size-optimized-shifts.c
@@ -0,0 +1,26 @@ 
+/* { dg-do compile } */
+/* { dg-options "-Os" } */
+/* { dg-final { scan-assembler-not "__mspabi_sral_4" } } */
+/* { dg-final { scan-assembler-not "__mspabi_srll_4" } } */
+/* { dg-final { scan-assembler-not "__mspabi_slll_4" } } */
+/* { dg-final { scan-assembler "__mspabi_sral" } } */
+/* { dg-final { scan-assembler "__mspabi_srll" } } */
+/* { dg-final { scan-assembler "__mspabi_slll" } } */
+
+/* Ensure that SImode shifts by a constant amount do not use the const_variant
+   of the shift library code when optimizing for size.  */
+
+long a;
+long b;
+long c;
+long d;
+unsigned long e;
+unsigned long f;
+
+void
+foo (void)
+{
+  a = b >> 4;
+  c = d << 4;
+  e = f >> 4;
+}
-- 
2.17.1