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Fix the FOR loop count formula (#1222)

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This commit is contained in:
Rangi
2023-11-07 17:43:46 -05:00
committed by GitHub
parent 5379e51094
commit 9fc088dcb0
4 changed files with 46 additions and 3 deletions
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10
src/asm/fstack.cpp
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@@ -240,7 +240,11 @@ bool yywrap(void)
// If this is a FOR, update the symbol value
if (contextStack->forName && fileInfo->iters[0] <= contextStack->nbReptIters) {
contextStack->forValue += contextStack->forStep;
// Avoid arithmetic overflow runtime error
uint32_t forValue = (uint32_t)contextStack->forValue +
(uint32_t)contextStack->forStep;
contextStack->forValue = forValue >= 0 ? (int32_t)forValue
: -(int32_t)~forValue - 1;
struct Symbol *sym = sym_AddVar(contextStack->forName,
contextStack->forValue);
@@ -513,9 +517,9 @@ void fstk_RunFor(char const *symName, int32_t start, int32_t stop, int32_t step,
uint32_t count = 0;
if (step > 0 && start < stop)
count = (stop - start - 1) / step + 1;
count = ((int64_t)stop - start - 1) / step + 1;
else if (step < 0 && stop < start)
count = (start - stop - 1) / -step + 1;
count = ((int64_t)start - stop - 1) / -(int64_t)step + 1;
else if (step == 0)
error("FOR cannot have a step value of 0\n");