===================================================================
@@ -9026,6 +9026,11 @@ The maximum number of conditional stores
if either vectorization (@option{-ftree-vectorize}) or if-conversion
(@option{-ftree-loop-if-convert}) is disabled. The default is 2.
+@item case-values-threshold
+The smallest number of different values for which it is best to use a
+jump-table instead of a tree of conditional branches. If the value is
+0, use the default for the machine. The default is 0.
+
@end table
@end table
===================================================================
@@ -0,0 +1,26 @@
+/* { dg-do compile { target { powerpc*-*-* } } } */
+/* { dg-skip-if "" { powerpc*-*-darwin* } { "*" } { "" } } */
+/* { dg-options "-O2 --param case-values-threshold=2" } */
+/* { dg-final { scan-assembler "mtctr" } } */
+/* { dg-final { scan-assembler "bctr" } } */
+
+/* Force using a dispatch table even though by default we would generate
+ ifs. */
+
+extern long call (long);
+
+long
+test_switch (long a, long b)
+{
+ long c;
+
+ switch (a)
+ {
+ case 0: c = -b; break;
+ case 1: c = ~b; break;
+ case 2: c = b+1; break;
+ default: c = b & 9; break;
+ }
+
+ return call (c) + 1;
+}
===================================================================
@@ -0,0 +1,32 @@
+/* { dg-do compile { target { powerpc*-*-* } } } */
+/* { dg-skip-if "" { powerpc*-*-darwin* } { "*" } { "" } } */
+/* { dg-options "-O2 --param case-values-threshold=20" } */
+/* { dg-final { scan-assembler-not "mtctr" } } */
+/* { dg-final { scan-assembler-not "bctr" } } */
+
+/* Force using if tests, instead of a dispatch table. */
+
+extern long call (long);
+
+long
+test_switch (long a, long b)
+{
+ long c;
+
+ switch (a)
+ {
+ case 0: c = -b; break;
+ case 1: c = ~b; break;
+ case 2: c = b+1; break;
+ case 3: c = b-2; break;
+ case 4: c = b*3; break;
+ case 5: c = b/4; break;
+ case 6: c = b<<5; break;
+ case 7: c = b>>6; break;
+ case 8: c = b|7; break;
+ case 9: c = b^8; break;
+ default: c = b&9; break;
+ }
+
+ return call (c) + 1;
+}
===================================================================
@@ -2946,7 +2946,7 @@ stmt.o : stmt.c $(CONFIG_H) $(SYSTEM_H)
$(LIBFUNCS_H) $(EXCEPT_H) $(RECOG_H) $(DIAGNOSTIC_CORE_H) \
output.h $(GGC_H) $(TM_P_H) langhooks.h $(PREDICT_H) $(OPTABS_H) \
$(TARGET_H) $(GIMPLE_H) $(MACHMODE_H) $(REGS_H) alloc-pool.h \
- $(PRETTY_PRINT_H) $(BITMAP_H)
+ $(PRETTY_PRINT_H) $(BITMAP_H) $(PARAMS_H)
except.o : except.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
$(TREE_H) $(FLAGS_H) $(EXCEPT_H) $(FUNCTION_H) $(EXPR_H) $(LIBFUNCS_H) \
langhooks.h insn-config.h hard-reg-set.h $(BASIC_BLOCK_H) output.h \
===================================================================
@@ -53,6 +53,7 @@ along with GCC; see the file COPYING3.
#include "alloc-pool.h"
#include "pretty-print.h"
#include "bitmap.h"
+#include "params.h"
/* Functions and data structures for expanding case statements. */
@@ -2270,6 +2271,20 @@ expand_switch_using_bit_tests_p (tree in
|| (uniq == 3 && count >= 6)));
}
+/* Return the smallest number of different values for which it is best to use a
+ jump-table instead of a tree of conditional branches. */
+
+static unsigned int
+case_values_threshold (void)
+{
+ unsigned int threshold = PARAM_VALUE (PARAM_CASE_VALUES_THRESHOLD);
+
+ if (threshold == 0)
+ threshold = targetm.case_values_threshold ();
+
+ return threshold;
+}
+
/* Terminate a case (Pascal/Ada) or switch (C) statement
in which ORIG_INDEX is the expression to be tested.
If ORIG_TYPE is not NULL, it is the original ORIG_INDEX
@@ -2424,7 +2439,7 @@ expand_case (gimple stmt)
If the switch-index is a constant, do it this way
because we can optimize it. */
- else if (count < targetm.case_values_threshold ()
+ else if (count < case_values_threshold ()
|| compare_tree_int (range,
(optimize_insn_for_size_p () ? 3 : 10) * count) > 0
/* RANGE may be signed, and really large ranges will show up
===================================================================
@@ -892,6 +892,16 @@ DEFPARAM (PARAM_MAX_STORES_TO_SINK,
"Maximum number of conditional store pairs that can be sunk",
2, 0, 0)
+/* Override CASE_VALUES_THRESHOLD of when to switch from doing switch
+ statements via if statements to using a table jump operation. If the value
+ is 0, the default CASE_VALUES_THRESHOLD will be used. */
+DEFPARAM (PARAM_CASE_VALUES_THRESHOLD,
+ "case-values-threshold",
+ "The smallest number of different values for which it is best to "
+ "use a jump-table instead of a tree of conditional branches, "
+ "if 0, use the default for the machine",
+ 0, 0, 0)
+
/*
Local variables: