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Fix code generation bug for indirect load/store of 64-bit values. 

The issue was that if a 64-bit value was being loaded via one pointer and stored via another, the load and store parts could both be using y for their indexing, but they would clash with each other, potentially leading to loads coming from the wrong place.

Here are some examples that illustrate the problem:

/* example 1 */
int main(void) {
        struct {
                char c[16];
                long long x;
        } s = {.x = 0x1234567890abcdef}, *sp = &s;
        long long ll, *llp = ≪
        *llp = sp->x;
        return ll != s.x; // should return 0
}

/* example 2 */
int main(void) {
        struct {
                char c[16];
                long long x;
        } s = {.x = 0x1234567890abcdef}, *sp = &s;
        long long ll, *llp = ≪
        unsigned i = 0;
        *llp = sp[i].x;
        return ll != s.x; // should return 0
}

/* example 3 */
int main(void) {
        long long x[2] = {0, 0x1234567890abcdef}, *xp = x;
        long long ll, *llp = ≪
        unsigned i = 1;
        *llp = xp[i];
        return ll != x[1]; // should return 0
}
This commit is contained in:
Stephen Heumann 2024-04-10 20:49:17 -05:00
parent 77e0b8fc59
commit 6b7414384f
2 changed files with 35 additions and 72 deletions
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105
Gen.pas
View File

@ -3283,81 +3283,44 @@ case optype of
gQuad := lQuad;
gQuad.where := gQuad.preference; {unless overridden later}
if gLong.where = inPointer then begin
if q = 0 then begin
if gLong.fixedDisp then begin
GenNative(m_ldy_imm, immediate, 6, nil, 0);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(6);
GenImplied(m_dey);
GenImplied(m_dey);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(4);
GenImplied(m_dey);
GenImplied(m_dey);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(2);
GenNative(m_lda_indl, direct, gLong.disp, nil, 0);
StoreWordOfQuad(0);
end {if}
if gLong.fixedDisp then begin
GenNative(m_ldy_imm, immediate, q+6, nil, 0);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(6);
GenNative(m_ldy_imm, immediate, q+4, nil, 0);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(4);
GenNative(m_ldy_imm, immediate, q+2, nil, 0);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(2);
if q = 0 then
GenNative(m_lda_indl, direct, gLong.disp, nil, 0)
else begin
GenImplied(m_tya);
GenImplied(m_clc);
GenNative(m_adc_imm, immediate, 6, nil, 0);
GenImplied(m_tay);
GenNative(m_ldy_imm, immediate, q, nil, 0);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(6);
GenImplied(m_dey);
GenImplied(m_dey);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(4);
GenImplied(m_dey);
GenImplied(m_dey);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(2);
GenImplied(m_dey);
GenImplied(m_dey);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(0);
end; {else}
end {if q = 0}
StoreWordOfQuad(0);
end {if}
else begin
if gLong.fixedDisp then begin
GenNative(m_ldy_imm, immediate, q+6, nil, 0);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(6);
GenImplied(m_dey);
GenImplied(m_dey);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(4);
GenImplied(m_dey);
GenImplied(m_dey);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(2);
GenImplied(m_dey);
GenImplied(m_dey);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(0);
end {if}
else begin
GenImplied(m_tya);
GenImplied(m_clc);
GenNative(m_adc_imm, immediate, q+6, nil, 0);
GenImplied(m_tay);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(6);
GenImplied(m_dey);
GenImplied(m_dey);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(4);
GenImplied(m_dey);
GenImplied(m_dey);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(2);
GenImplied(m_dey);
GenImplied(m_dey);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
StoreWordOfQuad(0);
end; {else}
gQuad.where := onStack;
GenImplied(m_tya);
GenImplied(m_clc);
GenNative(m_adc_imm, immediate, q+6, nil, 0);
GenImplied(m_tay);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
GenImplied(m_pha);
GenImplied(m_dey);
GenImplied(m_dey);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
GenImplied(m_pha);
GenImplied(m_dey);
GenImplied(m_dey);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
GenImplied(m_pha);
GenImplied(m_dey);
GenImplied(m_dey);
GenNative(m_lda_indly, direct, gLong.disp, nil, 0);
GenImplied(m_pha);
end; {else}
end {if glong.where = inPointer}
else if gLong.where = localAddress then begin

2
cc.notes
View File

@ -1622,7 +1622,7 @@ If you use #pragma debug 0x0010 to enable stack check debug code, the compiler w
16. When an expression of const- or volatile-qualified struct or union type was passed as a function parameter, incorrect code would be generated. This could lead to incorrect program behavior or crashes.
17. Incorrect code could sometimes be generated if a long long or unsigned long long value was a non-initial member of a structure, and it was accessed through a pointer to the structure and used as an operand of certain arithmetic, bitwise, or comparison operators.
17. Incorrect code could be generated in certain circumstances where a long long or unsigned long long member of a structure or array was accessed via a pointer.
-- Bugs from C 2.1.1 B3 that have been fixed in C 2.2.0 ---------------------