Hi there,
This patch intends to update thumb1_size_rtx_costs function to correctly
handle those RTXs defined by RTL expansion pass. Thus the GIMPLE
multiplication will be expanded to single mul instruction instead of a bunch
of shift/add/sub instructions which are in fact more expensive.
Tested with GCC regression test on QEMU ARM926, no regression. Is it OK to
trunk and 4.8 branch?
BR,
Terry
gcc/ChangeLog:
2013-07-24 Terry Guo <terry....@arm.com>
* config/arm/arm.c (thumb1_size_rtx_costs): Assign proper cost for
shift_add/shift_sub0/shift_sub1 RTXs.
gcc/testsuite/ChangeLog:
2013-07-24 Terry Guo <terry....@arm.com>
* gcc.target/arm/thumb1-Os-mult.c: New test case.diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index e6fd420..5c07832 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -7925,6 +7925,15 @@ thumb1_size_rtx_costs (rtx x, enum rtx_code code, enum
rtx_code outer)
case PLUS:
case MINUS:
+ /* Thumb-1 needs two instructions to fulfill shiftadd/shiftsub0/shiftsub1
+ defined by RTL expansion, especially for the expansion of
+ multiplication. */
+ if ((GET_CODE (XEXP (x, 0)) == MULT
+ && power_of_two_operand (XEXP (XEXP (x,0),1), SImode))
+ || (GET_CODE (XEXP (x, 1)) == MULT
+ && power_of_two_operand (XEXP (XEXP (x, 1), 1), SImode)))
+ return COSTS_N_INSNS (2);
+ /* On purpose fall through for normal RTX. */
case COMPARE:
case NEG:
case NOT:
diff --git a/gcc/testsuite/gcc.target/arm/thumb1-Os-mult.c
b/gcc/testsuite/gcc.target/arm/thumb1-Os-mult.c
new file mode 100644
index 0000000..31b8bd6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/thumb1-Os-mult.c
@@ -0,0 +1,12 @@
+/* { dg-require-effective-target arm_thumb1_ok } */
+/* { dg-do compile } */
+/* { dg-options "-Os" } */
+/* { dg-skip-if "" { ! { arm_thumb1 } } } */
+
+int
+mymul3 (int x)
+{
+ return x * 0x555;
+}
+
+/* { dg-final { scan-assembler "mul\[\\t \]*r.,\[\\t \]*r." } } */
