[MSP430,2/4] Emulate 16-bit shifts with rotate insn when src operand is originally in memory

Message ID 20190604141138.061f7e8f@jozef-kubuntu
State New
Headers show
Series
  • Reduce code size when performing bit shifts
Related show

Commit Message

Jozef Lawrynowicz June 4, 2019, 1:11 p.m.
This patch reduces code size by enabling the emulation of some 16-bit shift
instructions with the native rotate instructions, when the source operand is in
memory. This is achieved by forcing the source operand into a register.

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

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

With shift patch 1:
   text    data     bss     dec     hex filename
    484      12      20     516     204 a.out
With new patch:
   text    data     bss     dec     hex filename
    452      12      20     484     1e4 a.out

Ok for trunk?

Comments

Jeff Law June 5, 2019, 10:21 p.m. | #1
On 6/4/19 7:11 AM, Jozef Lawrynowicz wrote:
> This patch reduces code size by enabling the emulation of some 16-bit shift

> instructions with the native rotate instructions, when the source operand is in

> memory. This is achieved by forcing the source operand into a register.

> 

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

>   int a;

> 

>   int

>   main (void)

>   {

>     a = a << 4;

>     return 0;

>   }

> 

> With shift patch 1:

>    text    data     bss     dec     hex filename

>     484      12      20     516     204 a.out

> With new patch:

>    text    data     bss     dec     hex filename

>     452      12      20     484     1e4 a.out

> 

> Ok for trunk?

> 

> 

> 0002-MSP430-Force-the-src-operand-of-a-HImode-shift-into-.patch

> 

> From e609f63d49227ce385316896dde6a476f5f27db7 Mon Sep 17 00:00:00 2001

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

> Date: Mon, 13 May 2019 17:48:00 +0100

> Subject: [PATCH 2/4] MSP430: Force the src operand of a HImode shift into a

>  register if it is in memory

> 

> gcc/ChangeLog

> 

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

> 

> 	* config/msp430/msp430.md (ashlhi3): Force shift src operand into a

> 	register if it is in memory, so the shift can be emulated with a rotate

> 	instruction.

> 	(ashrhi3): Likewise.

> 	(lshrhi3): Likewise.

> 

> gcc/testsuite/ChangeLog

> 

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

> 

> 	* gcc.target/msp430/emulate-slli.c: New test.

> 	* gcc.target/msp430/emulate-srai.c: New test.

> 	* gcc.target/msp430/emulate-srli.c: New test.

OK
jeff
> ---

Patch

From e609f63d49227ce385316896dde6a476f5f27db7 Mon Sep 17 00:00:00 2001
From: Jozef Lawrynowicz <jozef.l@mittosystems.com>
Date: Mon, 13 May 2019 17:48:00 +0100
Subject: [PATCH 2/4] MSP430: Force the src operand of a HImode shift into a
 register if it is in memory

gcc/ChangeLog

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

	* config/msp430/msp430.md (ashlhi3): Force shift src operand into a
	register if it is in memory, so the shift can be emulated with a rotate
	instruction.
	(ashrhi3): Likewise.
	(lshrhi3): Likewise.

gcc/testsuite/ChangeLog

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

	* gcc.target/msp430/emulate-slli.c: New test.
	* gcc.target/msp430/emulate-srai.c: New test.
	* gcc.target/msp430/emulate-srli.c: New test.
---
 gcc/config/msp430/msp430.md                    | 15 +++++++++------
 gcc/testsuite/gcc.target/msp430/emulate-slli.c | 15 +++++++++++++++
 gcc/testsuite/gcc.target/msp430/emulate-srai.c | 15 +++++++++++++++
 gcc/testsuite/gcc.target/msp430/emulate-srli.c | 15 +++++++++++++++
 4 files changed, 54 insertions(+), 6 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/msp430/emulate-slli.c
 create mode 100644 gcc/testsuite/gcc.target/msp430/emulate-srai.c
 create mode 100644 gcc/testsuite/gcc.target/msp430/emulate-srli.c

diff --git a/gcc/config/msp430/msp430.md b/gcc/config/msp430/msp430.md
index 344d21d9378..58c1f4edc9c 100644
--- a/gcc/config/msp430/msp430.md
+++ b/gcc/config/msp430/msp430.md
@@ -756,8 +756,9 @@ 
 		   (match_operand:HI 2 "general_operand")))]
   ""
   {
-    if (GET_CODE (operands[1]) == SUBREG
-        && REG_P (XEXP (operands[1], 0)))
+    if ((GET_CODE (operands[1]) == SUBREG
+	 && REG_P (XEXP (operands[1], 0)))
+	|| MEM_P (operands[1]))
       operands[1] = force_reg (HImode, operands[1]);
     if (msp430x
         && REG_P (operands[0])
@@ -828,8 +829,9 @@ 
 		     (match_operand:HI 2 "general_operand")))]
   ""
   {
-    if (GET_CODE (operands[1]) == SUBREG
-        && REG_P (XEXP (operands[1], 0)))
+    if ((GET_CODE (operands[1]) == SUBREG
+	 && REG_P (XEXP (operands[1], 0)))
+	|| MEM_P (operands[1]))
       operands[1] = force_reg (HImode, operands[1]);
     if (msp430x
         && REG_P (operands[0])
@@ -916,8 +918,9 @@ 
 		     (match_operand:HI 2 "general_operand")))]
   ""
   {
-    if (GET_CODE (operands[1]) == SUBREG
-        && REG_P (XEXP (operands[1], 0)))
+    if ((GET_CODE (operands[1]) == SUBREG
+	 && REG_P (XEXP (operands[1], 0)))
+	|| MEM_P (operands[1]))
       operands[1] = force_reg (HImode, operands[1]);
     if (msp430x
         && REG_P (operands[0])
diff --git a/gcc/testsuite/gcc.target/msp430/emulate-slli.c b/gcc/testsuite/gcc.target/msp430/emulate-slli.c
new file mode 100644
index 00000000000..0ed09d55d8c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/msp430/emulate-slli.c
@@ -0,0 +1,15 @@ 
+/* { dg-do compile } */
+/* { dg-options "-Os" } */
+/* { dg-final { scan-assembler-not "mspabi_slli" } } */
+/* { dg-final { scan-assembler "rlax" } } */
+
+/* Ensure that HImode shifts with source operand in memory are emulated with a
+   rotate instructions.  */
+
+int a;
+
+void
+foo (void)
+{
+  a = a << 4;
+}
diff --git a/gcc/testsuite/gcc.target/msp430/emulate-srai.c b/gcc/testsuite/gcc.target/msp430/emulate-srai.c
new file mode 100644
index 00000000000..66291717a02
--- /dev/null
+++ b/gcc/testsuite/gcc.target/msp430/emulate-srai.c
@@ -0,0 +1,15 @@ 
+/* { dg-do compile } */
+/* { dg-options "-Os" } */
+/* { dg-final { scan-assembler-not "mspabi_srai" } } */
+/* { dg-final { scan-assembler "rrax" } } */
+
+/* Ensure that HImode shifts with source operand in memory are emulated with a
+   rotate instructions.  */
+
+int a;
+
+void
+foo (void)
+{
+  a = a >> 4;
+}
diff --git a/gcc/testsuite/gcc.target/msp430/emulate-srli.c b/gcc/testsuite/gcc.target/msp430/emulate-srli.c
new file mode 100644
index 00000000000..c10f30b2779
--- /dev/null
+++ b/gcc/testsuite/gcc.target/msp430/emulate-srli.c
@@ -0,0 +1,15 @@ 
+/* { dg-do compile } */
+/* { dg-options "-Os" } */
+/* { dg-final { scan-assembler-not "mspabi_srli" } } */
+/* { dg-final { scan-assembler "rrum" } } */
+
+/* Ensure that HImode shifts with source operand in memory are emulated with a
+   rotate instructions.  */
+
+unsigned int a;
+
+void
+foo (void)
+{
+  a = a >> 4;
+}
-- 
2.17.1