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Fix bug where the condition check of the ?: operator may be mis-evaluated.

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This could happen in certain cases where the condition codes might not be set at expected. The following program gives an example:

#pragma optimize 1
#include <stdio.h>
int one(void) {return 1;}
int negative_one(void) {return -1;}
int main(void) {
    puts((one() + negative_one()) ? "A" : "B");
}

This could also occur if the condition used the % operator, particularly after the recent changes to it.

Also, add unsigned multiplication, division, and modulo operations to the list of those that may not set the condition codes based on the result value, both in this and other contexts.

Detected based on several programs from FizzBuzz-C.
This commit is contained in:
Stephen Heumann 2018-09-14 00:22:10 -05:00
parent 60484d6f69
commit 8b4213cd5a
1 changed files with 3 additions and 4 deletions
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7
Gen.pas
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@ -404,7 +404,8 @@ begin {NeedsCondition}
NeedsCondition := opcode in
[pc_and,pc_ior,pc_cui,pc_cup,pc_lor,pc_lnd,pc_ldl,pc_lil,pc_lld,
pc_lli,pc_gil,pc_gli,pc_gdl,pc_gld,pc_iil,pc_ili,pc_idl,pc_ild,
pc_cop,pc_cpo,pc_cpi,pc_dvi,pc_mpi,pc_adi,pc_sbi,pc_mod,pc_bno];
pc_cop,pc_cpo,pc_cpi,pc_dvi,pc_mpi,pc_adi,pc_sbi,pc_mod,pc_bno,
pc_udi,pc_uim,pc_umi];
end; {NeedsCondition}
@ -5448,9 +5449,7 @@ procedure GenTree {op: icptr};
lab2 := GenLabel;
lab3 := GenLabel;
GenTree(op^.left);
if op^.left^.opcode in
[pc_and,pc_ior,pc_cui,pc_cup,pc_lor,pc_lnd,pc_ldl,pc_lil,pc_lld,
pc_lli,pc_gil,pc_gli,pc_gdl,pc_gld] then
if NeedsCondition(op^.left^.opcode) then
GenImplied(m_tax);
GenNative(m_beq, relative, lab1, nil, 0);
GenNative(m_brl, longrelative, lab2, nil, 0);