From e0de662f8e376461befdb57333a51d00cb5a6713 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Tue, 16 Jan 2024 01:08:16 +0100
Subject: [PATCH] fix signed word bitshift right (>8 shifts)

---
 .../prog8/optimizer/ExpressionSimplifier.kt   |  7 ++-
 compiler/test/arithmetic/bitshift.p8          | 16 -----
 examples/test.p8                              | 59 ++++---------------
 3 files changed, 16 insertions(+), 66 deletions(-)

diff --git a/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt b/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt
index f54d86283..b864cf1e4 100644
--- a/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt
+++ b/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt
@@ -836,14 +836,15 @@ class ExpressionSimplifier(private val program: Program,
                     return null
                 }
                 else if(amount == 8) {
-                    // shift right by 8 bits is just a byte operation: msb(X) as byte
+                    // shift right by 8 bits is just a byte operation: msb(X) as byte  (will get converted to word later)
                     val msb = FunctionCallExpression(IdentifierReference(listOf("msb"), expr.position), mutableListOf(expr.left), expr.position)
                     return TypecastExpression(msb, DataType.BYTE, true, expr.position)
                 }
                 else if(amount > 8) {
-                    // same as above but with residual shifts.
+                    // same as above but with residual shifts. Take care to do signed shift.
                     val msb = FunctionCallExpression(IdentifierReference(listOf("msb"), expr.position), mutableListOf(expr.left), expr.position)
-                    return TypecastExpression(BinaryExpression(msb, ">>", NumericLiteral.optimalInteger(amount - 8, expr.position), expr.position), DataType.BYTE, true, expr.position)
+                    val signed = TypecastExpression(msb, DataType.BYTE, true, expr.position)
+                    return BinaryExpression(signed, ">>", NumericLiteral.optimalInteger(amount - 8, expr.position), expr.position)
                 }
             }
             else -> {
diff --git a/compiler/test/arithmetic/bitshift.p8 b/compiler/test/arithmetic/bitshift.p8
index 38cf78a73..11cd3aff8 100644
--- a/compiler/test/arithmetic/bitshift.p8
+++ b/compiler/test/arithmetic/bitshift.p8
@@ -376,12 +376,6 @@ main {
         sw = shiftrsw15()
         txt.print_uwbin(sw as uword, true)
         txt.chrout('\n')
-        sw = shiftrsw16()
-        txt.print_uwbin(sw as uword, true)
-        txt.chrout('\n')
-        sw = shiftrsw17()
-        txt.print_uwbin(sw as uword, true)
-        txt.chrout('\n')
 
     }
 
@@ -555,16 +549,6 @@ main {
         return (q >> 15)
     }
 
-    sub shiftrsw16() -> word {
-        word @shared q = -12345
-        return (q >> 16)
-    }
-
-    sub shiftrsw17() -> word {
-        word @shared q = -12345
-        return (q >> 17)
-    }
-
 
 
 
diff --git a/examples/test.p8 b/examples/test.p8
index 3d2dbf037..1b728782b 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -4,9 +4,20 @@
 
 main {
     sub start() {
+        word @shared q = -12345
+        txt.print_w(q)
+        txt.nl()
+        txt.print_uwbin(q as uword, true)
+        txt.nl()
+        q >>=9
+        txt.print_w(q)
+        txt.nl()
+        txt.print_uwbin(q as uword, true)
+        txt.nl()
+
 ;        mem()
 ;        bytes()
-        words()
+;        words()
     }
 
     sub mem() {
@@ -29,11 +40,6 @@ main {
     sub bytes() {
         ubyte[]  wa = [$1a, $2b, $3c]
 
-        txt.print_ub(all(wa))
-        txt.spc()
-        txt.print_ub(any(wa))
-        txt.nl()
-
         txt.print_ubbin(wa[2], true)
         txt.nl()
         rol(wa[2])
@@ -54,47 +60,6 @@ main {
     sub words() {
         uword[]  wa = [$11aa, $22bb, $33cc]
         uword[]  @split swa = [$11aa, $22bb, $33cc]
-        uword[]  waone = [$0000, $3300, $0000]
-        uword[]  wazero = [$0000, $0000, $0000]
-        uword[]  @split swaone = [$0000, $3300, $0000]
-        uword[]  @split swazero = [$0000, $0000, $0000]
-
-        reverse(wa)
-        for cx16.r9 in wa {
-            txt.print_uwhex(cx16.r9, true)
-            txt.nl()
-        }
-        txt.nl()
-        reverse(swa)
-        for cx16.r9 in swa {
-            txt.print_uwhex(cx16.r9, true)
-            txt.nl()
-        }
-
-        txt.print_ub(all(wa))        ; 1
-        txt.spc()
-        txt.print_ub(any(wa))        ; 1
-        txt.nl()
-        txt.print_ub(all(waone))     ; 0
-        txt.spc()
-        txt.print_ub(any(waone))     ; 1
-        txt.nl()
-;        txt.print_ub(all(swaone))    ; 0
-;        txt.spc()
-        txt.print_ub(any(swaone))    ; 1
-        txt.nl()
-;        txt.print_ub(all(swa))       ; 1
-;        txt.spc()
-        txt.print_ub(any(swa))       ; 1
-        txt.nl()
-        txt.print_ub(all(wazero))    ; 0
-        txt.spc()
-        txt.print_ub(any(wazero))    ; 0
-        txt.nl()
-;        txt.print_ub(all(swazero))   ; 0
-;        txt.spc()
-        txt.print_ub(any(swazero))   ; 0
-        txt.nl()
 
         txt.print_uwbin(wa[2], true)
         txt.nl()