work around more commonly-unreachable 6g code sequences.

R=r
DELTA=23  (23 added, 0 deleted, 0 changed)
OCL=19405
CL=19420

diff --git a/src/cmd/cov/main.c b/src/cmd/cov/main.c
index 061f302677dd69b5a06f5250d1e00645dd616722..dbd9d0daec2e77e6c03ecf769490c0fc06b8daca 100644 (file)
--- a/src/cmd/cov/main.c
+++ b/src/cmd/cov/main.c
@@ -160,6 +160,29 @@ missing(uvlong pc, uvlong epc)
                        return;
        }
 
+       if(epc - pc == 2 || epc -pc == 3) {
+               // check for XORL inside shift.
+               // (on x86 have to implement large shift with explicit zeroing).
+               //      f+90 0x00002c9f CMPL    CX,$20
+               //      f+93 0x00002ca2 JCS     f+97(SB)
+               //      f+95 0x00002ca4 XORL    AX,AX <<<
+               //      f+97 0x00002ca6 SHLL    CL,AX
+               //      f+99 0x00002ca8 MOVL    $1,CX
+               //
+               //      f+c8 0x00002cd7 CMPL    CX,$40
+               //      f+cb 0x00002cda JCS     f+d0(SB)
+               //      f+cd 0x00002cdc XORQ    AX,AX <<<
+               //      f+d0 0x00002cdf SHLQ    CL,AX
+               //      f+d3 0x00002ce2 MOVQ    $1,CX
+               buf[0] = 0;
+               machdata->das(text, pc, 0, buf, sizeof buf);
+               if(strncmp(buf, "XOR", 3) == 0) {
+                       machdata->das(text, epc, 0, buf, sizeof buf);
+                       if(strncmp(buf, "SHL", 3) == 0 || strncmp(buf, "SHR", 3) == 0)
+                               return;
+               }
+       }
+
        // show first instruction to make clear where we were.
        machdata->das(text, pc, 0, buf, sizeof buf);