diff mbox

Simplify further in combine

Message ID 4D80D0B6.5090408@codesourcery.com
State New
Headers show

Commit Message

Chung-Lin Tang March 16, 2011, 3:01 p.m. UTC 
Hi,
this patch adds slightly more simplification in try_combine(), under
-fexpensive-optimizations, by calling subst() to both i2 and i1.
Supplied is an ARM testcase where this resulted in one less redundant
ZERO_EXTEND insn under ARMv6 and above.

Bootstrapped and tested on i686 and x86_64, cross-tested on ARM-Linux
using QEMU, all with no regressions. Okay for trunk?

Thanks,
Chung-Lin

2011-03-16  Chung-Lin Tang  <cltang@codesourcery.com>

	* combine.c (try_combine): Do simplification only call of
	subst() on i2 even when i1 is present. Update comments.

	testsuite/
	* gcc.target/arm/unsigned-extend-1.c: New testcase.

Comments

Richard Henderson March 16, 2011, 4:37 p.m. UTC | #1 
On 03/16/2011 08:01 AM, Chung-Lin Tang wrote:
> 	* combine.c (try_combine): Do simplification only call of
> 	subst() on i2 even when i1 is present. Update comments.
> 
> 	testsuite/
> 	* gcc.target/arm/unsigned-extend-1.c: New testcase.

Ok.


r~
diff mbox

Patch

Index: combine.c
===================================================================
--- combine.c	(revision 170996)
+++ combine.c	(working copy)
@@ -3063,7 +3063,7 @@ 
       /* It is possible that the source of I2 or I1 may be performing
 	 an unneeded operation, such as a ZERO_EXTEND of something
 	 that is known to have the high part zero.  Handle that case
-	 by letting subst look at the innermost one of them.
+	 by letting subst look at the inner insns.
 
 	 Another way to do this would be to have a function that tries
 	 to simplify a single insn instead of merging two or more
@@ -3088,11 +3088,9 @@ 
 	      subst_low_luid = DF_INSN_LUID (i1);
 	      i1src = subst (i1src, pc_rtx, pc_rtx, 0, 0);
 	    }
-	  else
-	    {
-	      subst_low_luid = DF_INSN_LUID (i2);
-	      i2src = subst (i2src, pc_rtx, pc_rtx, 0, 0);
-	    }
+
+	  subst_low_luid = DF_INSN_LUID (i2);
+	  i2src = subst (i2src, pc_rtx, pc_rtx, 0, 0);
 	}
 
       n_occurrences = 0;		/* `subst' counts here */
Index: testsuite/gcc.target/arm/unsigned-extend-1.c
===================================================================
--- testsuite/gcc.target/arm/unsigned-extend-1.c	(revision 0)
+++ testsuite/gcc.target/arm/unsigned-extend-1.c	(revision 0)
@@ -0,0 +1,9 @@ 
+/* { dg-do compile } */
+/* { dg-options "-O2 -march=armv6" } */
+
+unsigned char foo (unsigned char c)
+{
+  return (c >= '0') && (c <= '9');
+}
+
+/* { dg-final { scan-assembler-not "uxtb" } } */