From: Daniel Barboza <[email protected]>
Identify cases where a zero_one comparison is used to conditional
constant assignment and turn that into an unconditional PLUS. For the
code in PR71336:
int test(int a) {
return a & 1 ? 7 : 3;
}
We'll turn that into "(a&1) * (7 - 3) + 3", which yields the same
results but without the conditional, promoving more optimization
opportunities. In an armv8-a target the original code generates:
tst x0, 1 // 38 [c=8 l=4] *anddi3nr_compare0_zextract
mov w1, 3 // 41 [c=4 l=4] *movsi_aarch64/3
mov w0, 7 // 42 [c=4 l=4] *movsi_aarch64/3
csel w0, w1, w0, eq // 17 [c=4 l=4] *cmovsi_insn/0
ret // 47 [c=0 l=4] *do_return
With this transformation:
ubfiz w0, w0, 2, 1 // 7 [c=4 l=4] *andim_ashiftsi_bfiz
add w0, w0, 3 // 13 [c=4 l=4] *addsi3_aarch64/0
ret // 21 [c=0 l=4] *do_return
Similar gains are noticeable in RISC-V and x86.
For completeness sake we're also adding the variant "zero_one == 0".
Bootstrapped and regression tested in x86 and aarch64.
PR tree-optimization/71336
gcc/ChangeLog:
* match.pd(`zero_one EQ|NE 0 ? CST1:CST2`): New pattern.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/pr71336-2.c: New test.
* gcc.dg/tree-ssa/pr71336.c: New test.
---
gcc/match.pd | 36 ++++++++++++++
gcc/testsuite/gcc.dg/tree-ssa/pr71336-2.c | 59 +++++++++++++++++++++++
gcc/testsuite/gcc.dg/tree-ssa/pr71336.c | 20 ++++++++
3 files changed, 115 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr71336-2.c
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr71336.c
diff --git a/gcc/match.pd b/gcc/match.pd
index 7f16fd4e081..d041276c595 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -5195,6 +5195,42 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
&& expr_no_side_effects_p (@2))
(op (mult (convert:type @0) @2) @1))))
+/* PR71336:
+ zero_one != 0 ? CST1 : CST2 -> ((typeof (CST2))zero_one * diff) + CST2,
+ where CST1 > CST2 and diff = CST1 - CST2.
+
+ Includes the "zero_one == 0 ? (...)" variant too. */
+(for cmp (ne eq)
+ (simplify
+ (cond (cmp zero_one_valued_p@0 integer_zerop) INTEGER_CST@1 INTEGER_CST@2)
+ (with {
+ unsigned HOST_WIDE_INT diff = 0;
+
+ if (tree_int_cst_sgn (@1) > 0 && tree_int_cst_sgn (@2) > 0
+ && tree_fits_uhwi_p (@1) && tree_fits_uhwi_p (@2))
+ {
+ if (cmp == NE_EXPR
+ && wi::gtu_p (wi::to_wide (@1), wi::to_wide (@2)))
+ diff = tree_to_uhwi (@1) - tree_to_uhwi (@2);
+
+ if (cmp == EQ_EXPR
+ && wi::gtu_p (wi::to_wide (@2), wi::to_wide (@1)))
+ diff = tree_to_uhwi (@2) - tree_to_uhwi (@1);
+ }
+ }
+ (if (cmp == NE_EXPR
+ && INTEGRAL_TYPE_P (type)
+ && INTEGRAL_TYPE_P (TREE_TYPE (@0))
+ && diff > 0)
+ (plus (mult (convert:type @0) { build_int_cst (type, diff); })
+ @2)
+ (if (cmp == EQ_EXPR
+ && INTEGRAL_TYPE_P (type)
+ && INTEGRAL_TYPE_P (TREE_TYPE (@0))
+ && diff > 0)
+ (plus (mult (convert:type @0) { build_int_cst (type, diff); })
+ @1))))))
+
/* ?: Value replacement. */
/* a == 0 ? b : b + a -> b + a */
(for op (plus bit_ior bit_xor)
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr71336-2.c
b/gcc/testsuite/gcc.dg/tree-ssa/pr71336-2.c
new file mode 100644
index 00000000000..da44489d3e4
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr71336-2.c
@@ -0,0 +1,59 @@
+/* { dg-do run } */
+/* { dg-options "-O1" } */
+
+/* Macro adapted from builtin-object-size-common.h */
+#define FAIL() \
+ do { \
+ __builtin_printf ("Failure at line: %d\n", __LINE__); \
+ abort(); \
+ } while (0)
+
+void abort(void);
+
+int test (int a) {
+ return a & 1 ? 7 : 3;
+}
+
+int test2 (int a) {
+ return a & 1 ? 3 : 7;
+}
+
+int test3 (int a) {
+ return (a & 1) == 0 ? 3 : 7;
+}
+
+int test4 (int a) {
+ return (a & 1) == 0 ? 7 : 3;
+}
+
+int main (void) {
+ if (test (0) != 3)
+ FAIL ();
+ if (test (1) != 7)
+ FAIL ();
+ if (test (3) != 7)
+ FAIL ();
+
+ if (test2 (0) != 7)
+ FAIL ();
+ if (test2 (1) != 3)
+ FAIL ();
+ if (test2 (3) != 3)
+ FAIL ();
+
+ if (test3 (0) != 3)
+ FAIL ();
+ if (test3 (1) != 7)
+ FAIL ();
+ if (test3 (2) != 3)
+ FAIL ();
+
+ if (test4 (0) != 7)
+ FAIL ();
+ if (test4 (1) != 3)
+ FAIL ();
+ if (test4 (2) != 7)
+ FAIL ();
+
+ return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr71336.c
b/gcc/testsuite/gcc.dg/tree-ssa/pr71336.c
new file mode 100644
index 00000000000..fb643bf1eb3
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr71336.c
@@ -0,0 +1,20 @@
+/* { dg-additional-options -O1 } */
+/* { dg-additional-options -fdump-tree-gimple } */
+
+int test (int a) {
+ return a & 1 ? 7 : 3;
+}
+
+int test2 (int a) {
+ return (a & 1) == 0 ? 3 : 7;
+}
+
+int test3 (int a) {
+ return a & 1 ? 17 : 3;
+}
+
+int test4 (int a) {
+ return (a & 1) == 0 ? 3 : 17;
+}
+
+/* { dg-final { scan-tree-dump-times " goto " 0 gimple } } */
--
2.43.0
