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Remove undefined behavior from shifts

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`asl` and `asr` in `src/link/patch.c` courtesy of @pinobatch, and rearranged in RGBASM
evaluators.
This commit is contained in:
ISSOtm
2020-01-17 09:08:49 +01:00
parent 1bd41bf79a
commit b11d121c48
10 changed files with 244 additions and 37 deletions
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46
src/link/patch.c
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@@ -18,6 +18,47 @@
#include "extern/err.h"
static int32_t asl(int32_t value, int32_t shiftamt); // Forward decl for below
static int32_t asr(int32_t value, int32_t shiftamt)
{
uint32_t uvalue = value;
// Get the easy cases out of the way
if (shiftamt == 0)
return value;
if (value == 0 || shiftamt <= -32)
return 0;
if (shiftamt > 31)
return (value < 0) ? -1 : 0;
if (shiftamt < 0)
return asl(value, -shiftamt);
if (value > 0)
return uvalue >> shiftamt;
{
// Calculate an OR mask for sign extension
// 1->0x80000000, 2->0xC0000000, ..., 31->0xFFFFFFFE
uint32_t shiftamt_high_bits = -((uint32_t)1 << (32 - shiftamt));
return (uvalue >> shiftamt) | shiftamt_high_bits;
}
}
static int32_t asl(int32_t value, int32_t shiftamt)
{
// Repeat the easy cases here to avoid INT_MIN funny business
if (shiftamt == 0)
return value;
if (value == 0 || shiftamt >= 32)
return 0;
if (shiftamt < -31)
return (value < 0) ? -1 : 0;
if (shiftamt < 0)
return asr(value, -shiftamt);
return (uint32_t)value << shiftamt;
}
/* This is an "empty"-type stack */
struct RPNStack {
int32_t *buf;
@@ -182,14 +223,13 @@ static int32_t computeRPNExpr(struct Patch const *patch,
value = popRPN() <= value;
break;
/* FIXME: sanitize shifts */
case RPN_SHL:
value = popRPN();
value = popRPN() << value;
value = asl(popRPN(), value);
break;
case RPN_SHR:
value = popRPN();
value = popRPN() >> value;
value = asr(popRPN(), value);
break;
case RPN_BANK_SYM: