This adds a simple pattern to match.pd for `signbit(x) ? x : -x`
into abs<x>. This can be done for all types even ones that honor
signed zeros and NaNs because both signbit and - are considered
only looking at/touching the sign bit of those types and does
not trap either.
OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
PR tree-optimization/109829
gcc/ChangeLog:
* match.pd: Add pattern for `signbit(x) !=/== 0 ? x : -x`.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/abs-3.c: New test.
* gcc.dg/tree-ssa/abs-4.c: New test.
---
gcc/match.pd | 10 ++++++++++
gcc/testsuite/gcc.dg/tree-ssa/abs-3.c | 13 +++++++++++++
gcc/testsuite/gcc.dg/tree-ssa/abs-4.c | 13 +++++++++++++
3 files changed, 36 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/abs-3.c
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/abs-4.c
diff --git a/gcc/match.pd b/gcc/match.pd
index 26395880047..b025fb8facf 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -7439,6 +7439,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
&& TREE_CODE (@0) != INTEGER_CST)
(op @0 (ext @1 @2)))))
+/* signbit(x) != 0 ? -x : x -> abs(x)
+ signbit(x) == 0 ? -x : x -> -abs(x) */
+(for sign (SIGNBIT)
+ (for neeq (ne eq)
+ (simplify
+ (cond (neeq (sign @0) integer_zerop) (negate @0) @0)
+ (if (neeq == NE_EXPR)
+ (abs @0)
+ (negate (abs @0))))))
+
(simplify
/* signbit(x) -> 0 if x is nonnegative. */
(SIGNBIT tree_expr_nonnegative_p@0)
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/abs-3.c
b/gcc/testsuite/gcc.dg/tree-ssa/abs-3.c
new file mode 100644
index 00000000000..d2638e8f4c5
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/abs-3.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-optimized" } */
+/* PR tree-optimization/109829 */
+
+float abs_f(float x) { return __builtin_signbit(x) ? -x : x; }
+double abs_d(double x) { return __builtin_signbit(x) ? -x : x; }
+long double abs_ld(long double x) { return __builtin_signbit(x) ? -x : x; }
+
+
+/* __builtin_signbit(x) ? -x : x. Should be convert into ABS_EXP<x> */
+/* { dg-final { scan-tree-dump-not "signbit" "optimized"} } */
+/* { dg-final { scan-tree-dump-not "= -" "optimized"} } */
+/* { dg-final { scan-tree-dump-times "= ABS_EXPR" 3 "optimized"} } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/abs-4.c
b/gcc/testsuite/gcc.dg/tree-ssa/abs-4.c
new file mode 100644
index 00000000000..6197519faf7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/abs-4.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-optimized" } */
+/* PR tree-optimization/109829 */
+
+float abs_f(float x) { return __builtin_signbit(x) ? x : -x; }
+double abs_d(double x) { return __builtin_signbit(x) ? x : -x; }
+long double abs_ld(long double x) { return __builtin_signbit(x) ? x : -x; }
+
+
+/* __builtin_signbit(x) ? x : -x. Should be convert into - ABS_EXP<x> */
+/* { dg-final { scan-tree-dump-not "signbit" "optimized"} } */
+/* { dg-final { scan-tree-dump-times "= ABS_EXPR" 3 "optimized"} } */
+/* { dg-final { scan-tree-dump-times "= -" 3 "optimized"} } */
--
2.31.1
