From 2676acdd33957fe60f54ff9ec73fac8b7a6ed705 Mon Sep 17 00:00:00 2001
From: dos-reis <gdr@axiomatics.org>
Date: Mon, 26 Jul 2010 06:54:30 +0000
Subject: 	* algebra/si.spad.pamphlet (SingleInteger): Tidy. 	*
 interp/g-opt.boot (simplifyVMForm): Expand %icst0 and %icst1. 	(optIlt): Fold
 more configurations.

---
 src/interp/g-opt.boot | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'src/interp')

diff --git a/src/interp/g-opt.boot b/src/interp/g-opt.boot
index 85bee73c..2a2f5a60 100644
--- a/src/interp/g-opt.boot
+++ b/src/interp/g-opt.boot
@@ -147,6 +147,8 @@ resetTo(x,y) ==
 
 ++ Simplify the VM form `x'
 simplifyVMForm x ==
+  x = '%icst0 => 0
+  x = '%icst1 => 1
   isAtomicForm x => x
   x.op = 'CLOSEDFN => x
   atom x.op =>
@@ -440,6 +442,7 @@ $VMsideEffectFreeOperators ==
        CGREATERP GGREATERP CHAR GET BVEC_-GREATER %false %true
         %and %or %not %peq %ieq %ilt %ile %igt %ige %head %tail %integer?
          %beq %blt %ble %bgt %bge %bitand %bitior %bitnot %bcompl
+         %icst0 %icst1
           %imul %iadd %isub %igcd %ilcm %ipow %imin %imax %ieven? %iodd? %iinc
            %feq %flt %fle %fgt %fge %fmul %fadd %fsub %fexp %fmin %fmax %float?
             %fpow %fdiv %fneg %i2f %fminval %fmaxval %fbase %fprec %ftrunc
@@ -673,9 +676,14 @@ optIeq(x is ['%ieq,a,b]) ==
   x
 
 optIlt(x is ['%ilt,a,b]) ==
+  -- 1. Don't delay if both operands are literals.
   integer? a and integer? b =>
     a < b => '%true
     '%false
+  -- 2. max(a,b) cannot be negative if either a or b is zero.
+  b = 0 and a is ['%imax,:.] and (second a = 0 or third a = 0) => '%false
+  -- 3. min(a,b) cannot be positive if either a or b is zero.
+  a = 0 and b is ['%imin,:.] and (second b = 0 or third b = 0) => '%false
   x
 
 optIle(x is ['%ile,a,b]) ==
-- 
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