[PATCH][PR target/19201] Peephole to improve clearing items in structure for m68k

[PATCH][PR target/19201] Peephole to improve clearing items in structure for m68k

[Jeff Law]

[-- Attachment #1: Type: text/plain, Size: 1263 bytes --]


Every release I try to dig through some old bug reports and clear them 
out of the system.  This release is no different.

I'm a bit surprised I didn't tackle bz19201 in prior releases given that 
Kazu had an almost correct patch attached to the BZ.

I suspect this could be generalized to more than just clearing bytes. 
But I doubt it's worth any real effort as this is ultimately m68k specific.

Essentially Kazu's patch rewrites a load+store sequence where the load 
feeds the store's address computation.  He was missing a check to verify 
the that the target of the load was an address register.  That in turn 
causes failures such as reported by Mikael Pettersson in c#15 when he 
tried including the patch in his builds.

I was able to trigger the same kind of failure as Mikael using Kazu's 
patch and was able to confirm that adding the ADDRESS_REG_P check avoids 
those problems.

I've got a bootstrap running, but it'll be, umm, a long time before it 
finishes (both for the control build and the build with the updated 
patch).  The control build is into stage2 while the build with the patch 
is still building libraries for stage1.  But it's well past the point 
where it failed with the incorrect initial patch.

Installed on the trunk.

jeff




[-- Attachment #2: patch --]
[-- Type: text/plain, Size: 2817 bytes --]

commit 42582e91448c6afcc162d95229e14aac23a950ed
Author: Jeff Law <law@redhat.com>
Date:   Sun Dec 13 06:05:03 2015 -0700

    [PATCH][PR target/19201] Peephole to improve clearing items in structure for m68k
    	* config/m68k/m68k.md (load feeding clear byte): New peephole2.
    
    	* gcc.target/m68k/pr19201.c: New test.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index eee44a7..730c79f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2015-12-13  Kazu Kirata  <kazu@gcc.gnu.org>
+
+	* config/m68k/m68k.md (load feeding clear byte): New peephole2.
+
 2015-12-13  Tom de Vries  <tom@codesourcery.com>
 
 	* tree-ssa-structalias.c (find_func_clobbers): Handle sizes and kinds
diff --git a/gcc/config/m68k/m68k.md b/gcc/config/m68k/m68k.md
index 1eaf58f..444515a 100644
--- a/gcc/config/m68k/m68k.md
+++ b/gcc/config/m68k/m68k.md
@@ -7601,3 +7601,36 @@
 
 (include "cf.md")
 (include "sync.md")
+
+;; Convert
+;;
+;; 	move.l 4(%a0),%a0
+;; 	clr.b (%a0,%a1.l)
+;;
+;; into
+;;
+;; 	add.l 4(%a0),%a1
+;; 	clr.b (%a1)
+;;
+;; The latter is smaller.  It is faster on all models except m68060.
+
+(define_peephole2
+  [(set (match_operand:SI 0 "register_operand" "")
+	(mem:SI (plus:SI (match_operand:SI 1 "register_operand" "")
+			 (match_operand:SI 2 "const_int_operand" ""))))
+   (set (mem:QI (plus:SI (match_operand:SI 3 "register_operand" "")
+			 (match_operand:SI 4 "register_operand" "")))
+	(const_int 0))]
+  "(optimize_size || !TUNE_68060)
+   && (operands[0] == operands[3] || operands[0] == operands[4])
+   && ADDRESS_REG_P (operands[1])
+   && ADDRESS_REG_P ((operands[0] == operands[3]) ? operands[4] : operands[3])
+   && peep2_reg_dead_p (2, operands[3])
+   && peep2_reg_dead_p (2, operands[4])"
+  [(set (match_dup 5)
+	(plus:SI (match_dup 5)
+		 (mem:SI (plus:SI (match_dup 1)
+				  (match_dup 2)))))
+   (set (mem:QI (match_dup 5))
+	(const_int 0))]
+  "operands[5] = (operands[0] == operands[3]) ? operands[4] : operands[3];")
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 38d1dbe..3f0862e 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,7 @@
 2015-12-13  Jeff Law  <law@redhat.com>
 
+	* gcc.target/m68k/pr19201.c: New test.
+
 	* gcc.target/m68k/pr63347.c: Remove #include <stdlib> add -w to
 	command line options.
 	* gcc.target/m68k/20090709-1.c: Adjust expected output.
diff --git a/gcc/testsuite/gcc.target/m68k/pr19201.c b/gcc/testsuite/gcc.target/m68k/pr19201.c
new file mode 100644
index 0000000..dd81857
--- /dev/null
+++ b/gcc/testsuite/gcc.target/m68k/pr19201.c
@@ -0,0 +1,13 @@
+/* { dg-options "-w -O2 -fomit-frame-pointer" } */
+/* { dg-final { scan-assembler-not "%a.,%\[ad\]..l" } } */
+
+struct X { 
+  char *a; 
+  /* other members */ 
+  int b; 
+}; 
+ 
+void f (struct X *x) 
+{ 
+  x->a[x->b] = 0; 
+}

Re: [PATCH][PR target/19201] Peephole to improve clearing items in structure for m68k

[Andreas Schwab]

On Dez 13 2015, Jeff Law <law@redhat.com> wrote:

> diff --git a/gcc/config/m68k/m68k.md b/gcc/config/m68k/m68k.md
> index 1eaf58f..444515a 100644
> --- a/gcc/config/m68k/m68k.md
> +++ b/gcc/config/m68k/m68k.md
> @@ -7601,3 +7601,36 @@
>  
>  (include "cf.md")
>  (include "sync.md")
> +
> +;; Convert
> +;;
> +;; 	move.l 4(%a0),%a0
> +;; 	clr.b (%a0,%a1.l)
> +;;
> +;; into
> +;;
> +;; 	add.l 4(%a0),%a1
> +;; 	clr.b (%a1)
> +;;
> +;; The latter is smaller.  It is faster on all models except m68060.
> +
> +(define_peephole2
> +  [(set (match_operand:SI 0 "register_operand" "")
> +	(mem:SI (plus:SI (match_operand:SI 1 "register_operand" "")
> +			 (match_operand:SI 2 "const_int_operand" ""))))
> +   (set (mem:QI (plus:SI (match_operand:SI 3 "register_operand" "")
> +			 (match_operand:SI 4 "register_operand" "")))
> +	(const_int 0))]
> +  "(optimize_size || !TUNE_68060)
> +   && (operands[0] == operands[3] || operands[0] == operands[4])
> +   && ADDRESS_REG_P (operands[1])
> +   && ADDRESS_REG_P ((operands[0] == operands[3]) ? operands[4] : operands[3])

Shouldn't that use rtx_equal_p?

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."