Fix several cases where a condition might not be evaluated correctly.

These could occur because the code for certain operations was assumed to set the z flag based on the result value, but did not actually do so. The affected operations were shifts, loads or stores of bit-fields, and ? : expressions.

Here is an example showing the problem with a shift:

#pragma optimize 1
int main(void) {
        int i = 1, j = 0;
        return (i >> j) ? 1 : 0;
}

Here is an example showing the problem with a bit-field load:

struct {
        signed int i : 16;
} s = {1};
int main(void) {
        return (s.i) ? 1 : 0;
}

Here is an example showing the problem with a bit-field store:

#pragma optimize 1
struct {
        signed int i : 16;
} s;
int main(void) {
        return (s.i = 1) ? 1 : 0;
}

Here is an example showing the problem with a ? : expression:

#pragma optimize 1
int main(void) {
        int a = 5;
        return (a ? (a<<a) : 0) ? 0 : 1;
}

Gen.pas

@@ -621,7 +621,8 @@ 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_udi,pc_uim,pc_umi,pc_cnv,pc_rbo];
+    pc_udi,pc_uim,pc_umi,pc_cnv,pc_rbo,pc_shl,pc_shr,pc_usr,pc_lbf,
+    pc_lbu,pc_cbf,pc_tri];
 end; {NeedsCondition}
 
 

cc.notes

@@ -1863,6 +1863,8 @@ int foo(int[42]);
 
 200. Arithmetic operations on unsigned integer types should give the low-order bits of the true mathematical result in the event of overflow, but 16-bit unsigned multiplication did not always do this.
 
+201. When certain expressions were used for the condition in an if statement, loop, or conditional expression, the conditional branch might be evaluated incorrectly, leading to incorrect control flow.  The affected condition expressions included shifts, loads or stores of bit-fields, and ? : expressions.
+
 -- Bugs from C 2.1.0 that have been fixed -----------------------------------
 
 1.  In some situations, fread() reread the first 1K or so of the file.