multiplication by the constant 0 yields an
"mulgen botch" error in 6c and 8c.
this is probably a very rare case mostly used during debugging...
would this be worth fixing? and if yes, would the fix
below be in the right place?
theres a patch:
--- a/sys/src/cmd/6c/cgen.c Wed Mar 19 21:15:43 2014 +0100
+++ b/sys/src/cmd/6c/cgen.c Thu Mar 20 19:59:20 2014 +0100
@@ -309,6 +309,11 @@
/* fall thru */
case OMUL:
case OLMUL:
+ if((o == OMUL || o == OLMUL) && (r->vconst ==
0)){
+ cgen(l, Z);
+ zeroregm(nn);
+ goto done;
+ }
regalloc(&nod, l, nn);
cgen(l, &nod);
switch(o) {
@@ -621,6 +626,13 @@
reglcgen(&nod2, l, Z);
else
nod2 = *l;
+ if((o == OASMUL || o == OASLMUL) && (r->vconst
== 0)){
+ cgen(&nod2, Z);
+ zeroregm(&nod2);
+ if(nn != Z)
+ zeroregm(nn);
+ goto done;
+ }
regalloc(&nod, l, nn);
cgen(&nod2, &nod);
switch(o) {
test program:
#include <u.h>
#include <libc.h>
int bar(int a)
{
a *= 0;
return a;
}
int foo(int a)
{
return bar(a) * 0;
}
void
main(int argc, char *argv[])
{
foo(1);
}
--
cinap
