JIT: Fixed/re-added while loops (and DO for huge loops)

espruino · Nov 23, 2023 · bbceb23 · bbceb23
1 parent 1512b42
commit bbceb23
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Showing 3 changed files with 18 additions and 20 deletions.
diff --git a/ChangeLog b/ChangeLog
@@ -32,6 +32,7 @@
             nRF5x: when connecting to other devices, allow a slave latency of 2 (might increase reliability)
             Fix `Got [ERASED] expecting X` when storage compacts while executing a function *in* storage on non-Bangle devices (fix #2431)
             JIT: Fix crashes when code got too big for simple 2-byte jump instructions (fix #2433)
+            JIT: Fixed/re-added while loops (and DO for huge loops)
 
      2v19 : Fix Object.values/entries for numeric keys after 2v18 regression (fix #2375)
             nRF52: for SD>5 use static buffers for advertising and scan response data (#2367)

diff --git a/README_JIT.md b/README_JIT.md
@@ -173,22 +173,19 @@ jit(); // prints 0,1,2,3,4
 function jit() {"jit";for (var i=0;i<5;++i) print(i);}
 jit(); // prints 0,1,2,3,4
 
-/*
-// WHILE is broken, so disabled for now
-
 function jit() {"jit";while (0) {}}
 jit();
-E.setFlags({jitDebug:1});
 function jit() {"jit";while (1) return 42;}
 jit()==42
 function jit() {"jit";while (0) return 0;return 42;}
 jit()==42
 
+function jit(i) {"jit";while (i--) print(i);}
+jit(5) // prints 4,3,2,1,0
+
 function jit() {"jit";while (i--) j++;}
-i=1;j=0;jit();  // broken: Uncaught Error: Unable to assign value to non-reference ?
-function jit() {"jit";while (0) print(5); print("Done"); } jit(); // ok
-function jit() {"jit";while (1) print(5); print("Done"); } jit(); // Expecting a function to call, got Object (should print '5' forever)
-*/
+i=1;j=0;jit();  // ok, does nothing
+function jit() {"jit";while (0) print(5); print("Done"); } jit(); // prints 'Done'
 
 function jit() {"jit";do { print(i); } while (i--);}
 i=5;jit(); // prints 5,4,3,2,1,0

diff --git a/src/jsjit.c b/src/jsjit.c
@@ -982,27 +982,29 @@ void jsjStatementFor() {
 void jsjStatementDoOrWhile(bool isWhile) {
   int codePosStart = jsjcGetByteCount();
   if (isWhile) { // while loop
-    assert(0);
-    /*JSP_ASSERT_MATCH(LEX_R_WHILE);
+    JSP_ASSERT_MATCH(LEX_R_WHILE);
     DEBUG_JIT_EMIT("; WHILE condition\n");
     JSP_MATCH('(');
     jsjExpression();
+    if (jit.phase == JSJP_EMIT) {
+      // do this here so our stack counter stays at the right level
+      jsjPopAsBool(0);
+      jsjcCompareImm(0, 0);
+    }
     JSP_MATCH(')');
     DEBUG_JIT_EMIT("; Parsing WHILE main block\n");
     JsVar *oldBlock = jsjcStartBlock();
     jsjBlockOrStatement();
     JsVar *mainBlock = jsjcStopBlock(oldBlock);
     if (jit.phase == JSJP_EMIT) {
       DEBUG_JIT_EMIT("; WHILE condition jump\n");
-      jsjPopAsBool(0);
-      jsjcCompareImm(0, 0);
-      jsjcBranchConditionalRelative(JSJAC_EQ, jsvGetStringLength(mainBlock) + 2, JSJC_NONE);
+      jsjcBranchConditionalRelative(JSJAC_EQ, jsvGetStringLength(mainBlock) + 4, JSJC_FORCE_4BYTE);
       DEBUG_JIT_EMIT("; WHILE Main block\n");
       jsjcEmitBlock(mainBlock);
       DEBUG_JIT_EMIT("; WHILE jump back to condition\n");
-      jsjcBranchRelative(codePosStart - (jsjcGetByteCount()), JSJC_NONE);
+      jsjcBranchRelative(codePosStart - (jsjcGetByteCount()+4), JSJC_FORCE_4BYTE);
     }
-    jsvUnLock(mainBlock);*/
+    jsvUnLock(mainBlock);
   } else { // do..while loop
     JSP_ASSERT_MATCH(LEX_R_DO);
     DEBUG_JIT_EMIT("; DO Main block\n");
@@ -1015,7 +1017,7 @@ void jsjStatementDoOrWhile(bool isWhile) {
     if (jit.phase == JSJP_EMIT) {
       jsjPopAsBool(0);
       jsjcCompareImm(0, 0);
-      jsjcBranchConditionalRelative(JSJAC_NE, codePosStart - (jsjcGetByteCount()+2), JSJC_NONE);
+      jsjcBranchConditionalRelative(JSJAC_NE, codePosStart - (jsjcGetByteCount()+4), JSJC_FORCE_4BYTE);
     }
   }
 }
@@ -1060,10 +1062,8 @@ void jsjStatement() {
     return jsjStatementVar();
   } else if (lex->tk==LEX_R_IF) {
     return jsjStatementIf();
-  } else if (lex->tk==LEX_R_DO) {
-    return jsjStatementDoOrWhile(false);
-  /*} else if (lex->tk==LEX_R_WHILE) { // FIXME - WHILE loop seems somehow broken, so is disabled for now
-    return jsjStatementDoOrWhile(true);*/
+  } else if (lex->tk==LEX_R_DO || lex->tk==LEX_R_WHILE) {
+    return jsjStatementDoOrWhile(lex->tk==LEX_R_WHILE);
   } else if (lex->tk==LEX_R_FOR) {
     return jsjStatementFor();
   /*} else if (lex->tk==LEX_R_TRY) {