fix bug in stack overflow check.

if stack is in low memory and frame size is huge, test could wrap around!
fix by omitting test altogether if we know frame is big.

R=gri
OCL=14782
CL=14782

diff --git a/src/cmd/6l/pass.c b/src/cmd/6l/pass.c
index e071f6e1a95ed0de2063ba68bc6585c58882bd0d..fed9495c1773a7c1333b55eba947bbffb065506c 100644 (file)
--- a/src/cmd/6l/pass.c
+++ b/src/cmd/6l/pass.c
@@ -669,34 +669,36 @@ dostkoff(void)
                        q = P;
                        if(pmorestack != P)
                        if(!(p->from.scale & NOSPLIT)) {
-                               if(autoffset <= 75) {
-                                       // small stack
-                                       p = appendp(p);
-                                       p->as = ACMPQ;
-                                       p->from.type = D_SP;
-                                       p->to.type = D_INDIR+D_R15;
-                                       
-                               } else {
-                                       // large stack
-                                       p = appendp(p);
-                                       p->as = ALEAQ;
-                                       p->from.type = D_INDIR+D_SP;
-                                       p->from.offset = -(autoffset-75);
-                                       p->to.type = D_AX;
-
+                               if(autoffset < 4096) {  // do we need to call morestack
+                                       if(autoffset <= 75) {
+                                               // small stack
+                                               p = appendp(p);
+                                               p->as = ACMPQ;
+                                               p->from.type = D_SP;
+                                               p->to.type = D_INDIR+D_R15;
+                                               
+                                       } else {
+                                               // large stack
+                                               p = appendp(p);
+                                               p->as = ALEAQ;
+                                               p->from.type = D_INDIR+D_SP;
+                                               p->from.offset = -(autoffset-75);
+                                               p->to.type = D_AX;
+       
+                                               p = appendp(p);
+                                               p->as = ACMPQ;
+                                               p->from.type = D_AX;
+                                               p->to.type = D_INDIR+D_R15;
+                                       }
+       
+                                       // common
                                        p = appendp(p);
-                                       p->as = ACMPQ;
-                                       p->from.type = D_AX;
-                                       p->to.type = D_INDIR+D_R15;
+                                       p->as = AJHI;
+                                       p->to.type = D_BRANCH;
+                                       p->to.offset = 4;
+                                       q = p;
                                }
 
-                               // common
-                               p = appendp(p);
-                               p->as = AJHI;
-                               p->to.type = D_BRANCH;
-                               p->to.offset = 4;
-                               q = p;
-
                                p = appendp(p);
                                p->as = AMOVQ;
                                p->from.type = D_CONST;

diff --git a/test/bugs/bug092.go b/test/fixedbugs/bug092.go
similarity index 100%
rename from test/bugs/bug092.go
rename to test/fixedbugs/bug092.go

diff --git a/test/golden.out b/test/golden.out
index da9ff597f32465e2e7774e7ea08ea3dfaebd67aa..fd062fa9a7019717c36aee0d52f14bc0ce9d10d3 100644 (file)
--- a/test/golden.out
+++ b/test/golden.out
@@ -145,10 +145,6 @@ BUG: fails incorrectly
 =========== bugs/bug090.go
 BUG: compilation succeeds incorrectly
 
-=========== bugs/bug092.go
-BUG should not crash
-$RUNFILE: line 1: PID Illegal instruction     ./$A.out
-
 =========== fixedbugs/bug015.go
 fixedbugs/bug015.go:7: overflow converting constant to <int64>INT64