Hi,
This patch adds a mid-end check to catch division by
constant case and optimize it to generate one shift,
instead of two.
A testacase to check the correct codegeneration for aarch64
is added. This check is not made generic, because the optimisation
implemented is not used by all targets.
Is it ok?
Thanks,
Alex
gcc/
2014-11-03 Alex Velenko alex.vele...@arm.com
* simplify-rtx.c (simplify_binary_operation_1): Div check added.
* rtl.h (SUBREG_P): New macro added.
gcc/testsuite/
2014-11-03 Alex Velenko alex.vele...@arm.com
* gcc.dg/asr-div1.c : New testcase.
From 471fbb2057b4d338d01bb403f0973adbed33a31d Mon Sep 17 00:00:00 2001
From: Alex Velenko alex.vele...@arm.com
Date: Mon, 6 Oct 2014 15:33:36 +0100
Subject: [PATCH] [RTL, Patch] Int div by constant compilation enhancement
This patch adds a mid-end check to catch division by
constant case and optimize it to generate one shift,
instead of two.
A testacase to check the correct codegeneration for aarch64
is added. This check is not made generic, because the optimisation
implemented is not used by all targets.
Thanks,
Alex
gcc/
2014-11-03 Alex Velenko alex.vele...@arm.com
* simplify-rtx.c (simplify_binary_operation_1): Div check added.
* rtl.h (SUBREG_P): New macro added.
gcc/testsuite/
2014-11-03 Alex Velenko alex.vele...@arm.com
* gcc.dg/asr-div1.c : New testcase.
---
gcc/rtl.h | 3 +++
gcc/simplify-rtx.c | 38
gcc/testsuite/gcc.dg/asr_div1.c | 56 +
3 files changed, 97 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/asr_div1.c
diff --git a/gcc/rtl.h b/gcc/rtl.h
index ddd39c9..6222817 100644
--- a/gcc/rtl.h
+++ b/gcc/rtl.h
@@ -789,6 +789,9 @@ struct GTY(()) rtvec_def {
/* Predicate yielding nonzero iff X is a data for a jump table. */
#define JUMP_TABLE_DATA_P(INSN) (GET_CODE (INSN) == JUMP_TABLE_DATA)
+/* Predicate yielding nonzero iff RTX is a subreg. */
+#define SUBREG_P(RTX) (GET_CODE (RTX) == SUBREG)
+
template
template
inline bool
diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index d783c22..e01fba7 100644
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -3102,6 +3102,44 @@ simplify_binary_operation_1 (enum rtx_code code, enum machine_mode mode,
UINTVAL (trueop0) == GET_MODE_MASK (mode)
! side_effects_p (op1))
return op0;
+ /* Given:
+ scalar modes M1, M2
+ scalar constants c1, c2
+ size (M2) size (M1)
+ c1 == size (M2) - size (M1)
+ optimize:
+ (ashiftrt:M1 (subreg:M1 (lshiftrt:M2 (reg:M2)
+ (const_int c1))
+ low_part)
+ (const_int c2))
+ to:
+ (subreg:M1 (ashiftrt:M2 (reg:M2)
+ (const_int c1 + c2))
+ low_part). */
+ if (!VECTOR_MODE_P (mode)
+ SUBREG_P (op0)
+ CONST_INT_P (op1)
+ (GET_CODE (SUBREG_REG (op0)) == LSHIFTRT)
+ !VECTOR_MODE_P (GET_MODE (SUBREG_REG (op0)))
+ CONST_INT_P (XEXP (SUBREG_REG (op0), 1))
+ (GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (op0)))
+ GET_MODE_BITSIZE (mode))
+ (INTVAL (XEXP (SUBREG_REG (op0), 1))
+ == (GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (op0)))
+ - GET_MODE_BITSIZE (mode)))
+ subreg_lowpart_p (op0))
+{
+ rtx tmp = GEN_INT (INTVAL (XEXP (SUBREG_REG (op0), 1))
+ + INTVAL (op1));
+ machine_mode inner_mode = GET_MODE (SUBREG_REG (op0));
+ tmp = simplify_gen_binary (ASHIFTRT,
+ GET_MODE (SUBREG_REG (op0)),
+ XEXP (SUBREG_REG (op0), 0),
+ tmp);
+ return simplify_gen_subreg (mode, tmp, inner_mode,
+ subreg_lowpart_offset (mode,
+ inner_mode));
+}
canonicalize_shift:
if (SHIFT_COUNT_TRUNCATED CONST_INT_P (op1))
{
diff --git a/gcc/testsuite/gcc.dg/asr_div1.c b/gcc/testsuite/gcc.dg/asr_div1.c
new file mode 100644
index 000..61430ca
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/asr_div1.c
@@ -0,0 +1,56 @@
+/* Test division by const int generates only one shift. */
+/* { dg-do run } */
+/* { dg-options -O2 -fdump-rtl-combine-all } */
+
+extern void abort (void);
+
+#define NOINLINE __attribute__((noinline))
+
+static NOINLINE int
+f1 (int n)
+{
+ return n / 33;
+}
+
+static NOINLINE int
+f2 (int n)
+{
+ return n / 77;
+}
+
+int
+main ()
+{
+ int a = 0x;
+ int b = 0x;
+ int c;
+ c = f1 (a);
+ if (c != 0xfd6a052c)
+abort ();
+ c = f1 (b);
+ if (c != 0x295FAD4)
+abort ();
+ c = f2 (a);
+ if (c != 0xfee44b5c)
+abort ();
+ c = f2 (b);
+ if (c != 0x11bb4a4)
+abort ();
+ return
