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When optimizing certain index calculations, properly indicate whether they should be signed or unsigned.

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This type information is currently used when generating code for the large memory model, but not for the short memory model (which is a bug in itself, causing issue such as #45).

Because the correct type information was not being provided, the code generator could incorrectly use signed index computations when a 16-bit unsigned index value was used in large-memory-model code. The following program is an example that was being miscompiled:

#pragma optimize 1
#pragma memorymodel 1

char c[0xFFFF];

int main(void) {
    unsigned i = 0xABCD;
    c[0xABCD] = 3;
    return c[i]; /* should return 3 */
}
This commit is contained in:
Stephen Heumann 2017-11-01 23:20:34 -05:00
parent 730544a6ce
commit 763c5192df
1 changed files with 8 additions and 0 deletions
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8
DAG.pas
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@ -822,6 +822,10 @@ case op^.opcode of {check for optimizations of this node}
end; {with}
op^.right^.opcode := pc_shl;
op^.opcode := pc_ixa;
if fromType.optype in [cgByte,cgWord] then
op^.optype := cgWord
else
op^.optype := cgUWord;
PeepHoleOptimization(opv);
end; {if}
end; {if}
@ -836,6 +840,10 @@ case op^.opcode of {check for optimizations of this node}
else
op^.right := op^.right^.left;
op^.opcode := pc_ixa;
if fromType.optype in [cgByte,cgWord] then
op^.optype := cgWord
else
op^.optype := cgUWord;
PeepHoleOptimization(opv);
end; {if}
end; {else if}