On AArch64 the UXTB and UXTH instructions are aliases of UBFM,

which does a shift as part of its operation. An AND immediate is a
simpler operation, and might be faster on some implementations, so
it is better to emit this this instead of UBFM.

Benchmarking showed no difference on implementations where UBFM has
the same performance as AND, and minor speedups across several
benchmarks on an implementation where UBFM is slower than AND.

Bootstrapped and tested on aarch64-none-elf.

    gcc/
	* config/aarch64/aarch64.md
	(zero_extend<SHORT:mode><GPI:mode>2_aarch64): Change output
	statement and type.
	(<optab>qihi2_aarch64): Likewise, and split into two.
	(extendqihi2_aarch64): New.
	(zero_extendqihi2_aarch64): New.
	* config/aarch64/iterators.md (ldrxt): Remove.
	* config/aarch64/aarch64.c (aarch64_rtx_costs): Change cost of
	uxtb/uxth.

From-SVN: r238821

gcc/ChangeLog

 2016-07-28  Kristina Martsenko  <kristina.martsenko@arm.com>
+2016-07-28  Wilco Dijkstra  <wdijkstr@arm.com>
+
+	 * config/aarch64/aarch64.md
+	(zero_extend<SHORT:mode><GPI:mode>2_aarch64): Change output
+	statement and type.
+	(<optab>qihi2_aarch64): Likewise, and split into two.
+	(extendqihi2_aarch64): New.
+	(zero_extendqihi2_aarch64): New.
+	* config/aarch64/iterators.md (ldrxt): Remove.
+	* config/aarch64/aarch64.c (aarch64_rtx_costs): Change cost of
+	uxtb/uxth.
+
+2016-07-28  Kristina Martsenko  <kristina.martsenko@arm.com>
 
 	* config/aarch64/aarch64.c (aarch64_rtx_costs): Fix cost of zero extend.
 

gcc/config/aarch64/aarch64.c

@@ -6838,8 +6838,8 @@ cost_plus:
 	    }
 	  else
 	    {
-	      /* UXTB/UXTH.  */
-	      *cost += extra_cost->alu.extend;
+	      /* We generate an AND instead of UXTB/UXTH.  */
+	      *cost += extra_cost->alu.logical;
 	    }
 	}
       return false;

gcc/config/aarch64/aarch64.md

@@ -1577,10 +1577,10 @@
         (zero_extend:GPI (match_operand:SHORT 1 "nonimmediate_operand" "r,m,m")))]
   ""
   "@
-   uxt<SHORT:size>\t%<GPI:w>0, %w1
+   and\t%<GPI:w>0, %<GPI:w>1, <SHORT:short_mask>
    ldr<SHORT:size>\t%w0, %1
    ldr\t%<SHORT:size>0, %1"
-  [(set_attr "type" "extend,load1,load1")]
+  [(set_attr "type" "logic_imm,load1,load1")]
 )
 
 (define_expand "<optab>qihi2"
@@ -1589,16 +1589,26 @@
   ""
 )
 
-(define_insn "*<optab>qihi2_aarch64"
+(define_insn "*extendqihi2_aarch64"
   [(set (match_operand:HI 0 "register_operand" "=r,r")
-        (ANY_EXTEND:HI (match_operand:QI 1 "nonimmediate_operand" "r,m")))]
+	(sign_extend:HI (match_operand:QI 1 "nonimmediate_operand" "r,m")))]
   ""
   "@
-   <su>xtb\t%w0, %w1
-   <ldrxt>b\t%w0, %1"
+   sxtb\t%w0, %w1
+   ldrsb\t%w0, %1"
   [(set_attr "type" "extend,load1")]
 )
 
+(define_insn "*zero_extendqihi2_aarch64"
+  [(set (match_operand:HI 0 "register_operand" "=r,r")
+	(zero_extend:HI (match_operand:QI 1 "nonimmediate_operand" "r,m")))]
+  ""
+  "@
+   and\t%w0, %w1, 255
+   ldrb\t%w0, %1"
+  [(set_attr "type" "logic_imm,load1")]
+)
+
 ;; -------------------------------------------------------------------
 ;; Simple arithmetic
 ;; -------------------------------------------------------------------

gcc/config/aarch64/iterators.md

@@ -942,9 +942,6 @@
 ;; Similar, but when not(op)
 (define_code_attr nlogical [(and "bic") (ior "orn") (xor "eon")])
 
-;; Sign- or zero-extending load
-(define_code_attr ldrxt [(sign_extend "ldrs") (zero_extend "ldr")])
-
 ;; Sign- or zero-extending data-op
 (define_code_attr su [(sign_extend "s") (zero_extend "u")
 		      (sign_extract "s") (zero_extract "u")