[DTrace-devel] [PATCH 6/6] Disassembler: coding-style taste test

[eugene.loh at oracle.com]

From: Eugene Loh <eugene.loh at oracle.com>

The previous patch for the disassembler replaces
    dt_dis_varname()
with
    dt_dis_varname_id() and
    dt_dis_varname_off()

Since the two new functions are very similar, this patch proposes
a preprocessor macro that essentially implements both, making each
function basically a one-liner.  Is this an improvement?  I don't
know.  Take a look.

This patch should either be discarded or squashed into the earlier
disassembler patch.  The earlier commit message could be used without
change.

Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
---
 libdtrace/dt_dis.c | 38 ++++++++++++++++----------------------
 1 file changed, 16 insertions(+), 22 deletions(-)

diff --git a/libdtrace/dt_dis.c b/libdtrace/dt_dis.c
index 1a589bca..5505b339 100644
--- a/libdtrace/dt_dis.c
+++ b/libdtrace/dt_dis.c
@@ -44,23 +44,27 @@ reg(int r)
 	return name[r];
 }
 
+#define DT_DIS_VARNAME_LOOKUP(field, x) \
+	for (i = 0; i < dp->dtdo_varlen; i++) { \
+		const dtrace_difv_t *dvp = &dp->dtdo_vartab[i]; \
+		if (dvp->field == (x) && \
+		    dvp->dtdv_scope == scope && \
+		    dvp->dtdv_insn_from <= addr && \
+		    dvp->dtdv_insn_to >= addr) { \
+			if (dvp->dtdv_name < dp->dtdo_strlen) \
+				return dp->dtdo_strtab + dvp->dtdv_name; \
+			break; \
+		} \
+	} \
+	return NULL
+
 static const char *
 dt_dis_varname_id(const dtrace_difo_t *dp, uint_t id, uint_t scope, uint_t addr)
 {
-	const dtrace_difv_t *dvp = dp->dtdo_vartab;
 	uint_t i;
 
 	id &= 0x0fff;
-	for (i = 0; i < dp->dtdo_varlen; i++, dvp++) {
-		if (dvp->dtdv_id == id && dvp->dtdv_scope == scope &&
-		    dvp->dtdv_insn_from <= addr && addr <= dvp->dtdv_insn_to) {
-			if (dvp->dtdv_name < dp->dtdo_strlen)
-				return dp->dtdo_strtab + dvp->dtdv_name;
-			break;
-		}
-	}
-
-	return NULL;
+	DT_DIS_VARNAME_LOOKUP(dtdv_id, id); /* look up by id */
 }
 
 static const char *
@@ -68,17 +72,7 @@ dt_dis_varname_off(const dtrace_difo_t *dp, uint_t off, uint_t scope, uint_t add
 {
 	uint_t i;
 
-	for (i = 0; i < dp->dtdo_varlen; i++) {
-		const dtrace_difv_t *dvp = &dp->dtdo_vartab[i];
-		if (dvp->dtdv_offset == off && dvp->dtdv_scope == scope &&
-		    dvp->dtdv_insn_from <= addr && addr <= dvp->dtdv_insn_to) {
-			if (dvp->dtdv_name < dp->dtdo_strlen)
-				return dp->dtdo_strtab + dvp->dtdv_name;
-			break;
-		}
-	}
-
-	return NULL;
+	DT_DIS_VARNAME_LOOKUP(dtdv_offset, off); /* look up by offset */
 }
 
 /*ARGSUSED*/
-- 
2.18.4