More optimiser idioms (by Joris Huizer)

diff --git a/NEWS.txt b/NEWS.txt
index cb7b4d961309fe773298f7d0b7c5945faace3f99..4abc48e329f6339aed8bcf92da76cb323711689e 100644 (file)
--- a/NEWS.txt
+++ b/NEWS.txt
@@ -60,8 +60,9 @@ Changes by Joris Huizer
 11. The -g option now causes optimisation of the output compiled C to be
     turned off, and adds comments to the output file the same way -c does.
 
-12. Added new optimiser idioms [cxorand16] and [cxorand32] for situations
-    where AND and XOR together are used to simulate AND and bitwise-not;
+
+12. Added more optimiser idioms: [cxorand16], [cxorand32], [cfoldintoorinand],
+    [or16and], [xor16and], [lshift32half], [rshiftoutofneg], [andoutofneg];
     also generalised the idiom-matching code to compare 16-bit and 32-bit
     constants as equal if they have the same value, and fixed some typos in
     the current 16-bit complement idioms.

diff --git a/src/idiotism.oil b/src/idiotism.oil
index 4af6f7b788336bb379e3c3608403a5408230263d..5ab8997f1c52430af7719614b506937929e8ebb3 100644 (file)
--- a/src/idiotism.oil
+++ b/src/idiotism.oil
@@ -66,6 +66,9 @@
 (#{1}1 == #{1}2)->(#{x1 == x2}0)
 (#{1}1 != #{1}2)->(#{x1 != x2}0)
 
+; Reducing constants inside a C or operation can help to recognize idioms
+[cfoldintoorinand]
+(((_1) | #{1}2) & #{1}3)->(((_1) | #{x2 & x3}0) & _3)
 
 ; Binary bitwise optimizations
 [cbinand]
@@ -135,7 +138,7 @@
 ((?32(_{!(c&1431655765LU)}2|_{!(c&2863311530LU)}1))&
  #{!(x&2863311530LU)&&iselect(x,1431655765LU)==xselx(iselect(x,1431655765LU))}3
 )->(((_2 >> #1) ^ _1) & _3)
-  
+
 ; Bitwise complements. (The INTERCAL which ultimately leads to cases 3 and 4
 ; is not the most efficient way to do this, by the way.)
 [cnot1]
@@ -198,6 +201,16 @@
 ((_1~#1431655765)$_2)->(((_1&#1431655765)<<#1)|(#0$_2))
 [selectmingle4]
 (_1$(_2~#2863311530))->(((_2&#2863311530)>>#1)|(_1$#0))
+[selectmingle5]
+((_{!(c&4294901760UL)}1$_{!(c&4294901760UL)}2)~#3579139412)
+->((_1&#32768)|(_2>>#1))
+
+; special cases of V16/?16; the top bit was 0, so becomes equal to the
+; bottom bit
+[or16and]
+((V16 _{!(c&4294934528UL)}1)&#32768)->((_1&#1)<<#15)
+[xor16and]
+((?16 _{!(c&4294934528UL)}1)&#32768)->((_1&#1)<<#15)
 
 ; Shifts
 
@@ -238,6 +251,8 @@
 ->((((_1>>#{r}0)~#{iselect(x3>>(r*2+1),1431655765LU)}0)
     <<#{setbitcount(x3&((2LU<<(r*2))-1))}0)|#{iselect(mingle(x4,x2),x3)}0)
 >
+
+
 ; 32-bit leftshift by 1; there are 8 ways to write this.
 [lshift32by1]
 (((_1&#1431655765)<<#1)|((_1&#715827882)<<#1))->((_1&#2147483647)<<#1)
@@ -248,6 +263,19 @@
 (((_1&#715827882)<<#1)|((#1431655765&_1)<<#1))->((_1&#2147483647)<<#1)
 (((#715827882&_1)<<#1)|((_1&#1431655765)<<#1))->((_1&#2147483647)<<#1)
 (((#715827882&_1)<<#1)|((#1431655765&_1)<<#1))->((_1&#2147483647)<<#1)
+
+; a weird part of a leftshift
+[lshift32half]
+(#0$((:1&#2863311530)~#715827883))->((:1&#2863311530)<<#1)
+
+; Move rshift, AND out of neg
+[rshiftoutofneg]
+(~16 (.1 >> #{1}2))->(((~16 .1) >> _2) | #32768)
+(~32 (:1 >> #{1}2))->(((~32 :1) >> _2) | #2147483648)
+[andoutofneg]
+(~16 (.1 & #{1}2))->(((~16 .1) & _2) | #{(~x2)&65535}0)
+(~32 (:1 & #{1}2))->(((~32 :1) & _2) | #{~x2}0)
+
 ; Move AND inside shifts, and OR and XOR outside shifts
 [andintoshift]
 ((_1 << #{1}2) & #{1}3)->((_1 & #{x3>>x2}0) << _2)
@@ -548,4 +576,4 @@
 ; Thanks to Joris Huizer for suggesting the idea behind the next one;
 ; this is a more general idiom than the suggested [triplenot].
 [redundantdoublenot]
-(!(!(_{c==1}1)))->(_1)
\ No newline at end of file
+(!(!(_{c==1}1)))->(_1)