From 5bfc8303ffe2d86e938d45f13cd99a39469dac4f Mon Sep 17 00:00:00 2001 From: Wilco Dijkstra Date: Wed, 12 Feb 2020 18:23:21 +0000 Subject: [PATCH] [AArch64] Set ctz rtx_cost (PR93565) Combine sometimes behaves oddly and duplicates ctz to remove an unnecessary sign extension. Avoid this by setting the cost for ctz to be higher than that of a simple ALU instruction. Deepsjeng performance improves by ~0.6%. gcc/ PR rtl-optimization/93565 * config/aarch64/aarch64.c (aarch64_rtx_costs): Add CTZ costs. testsuite/ PR rtl-optimization/93565 * gcc.target/aarch64/pr93565.c: New test. --- gcc/ChangeLog | 5 ++++ gcc/config/aarch64/aarch64.c | 7 +++++ gcc/testsuite/ChangeLog | 5 ++++ gcc/testsuite/gcc.target/aarch64/pr93565.c | 34 ++++++++++++++++++++++ 4 files changed, 51 insertions(+) create mode 100644 gcc/testsuite/gcc.target/aarch64/pr93565.c diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 36e75b35fb8..735cc47a3dd 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2020-02-12 Wilco Dijkstra + + PR rtl-optimization/93565 + * config/aarch64/aarch64.c (aarch64_rtx_costs): Add CTZ costs. + 2020-02-12 Wilco Dijkstra * config/aarch64/aarch64-simd.md diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c index 6a1b4099af1..4a34dce5d79 100644 --- a/gcc/config/aarch64/aarch64.c +++ b/gcc/config/aarch64/aarch64.c @@ -11507,6 +11507,13 @@ aarch64_rtx_costs (rtx x, machine_mode mode, int outer ATTRIBUTE_UNUSED, return false; + case CTZ: + *cost = COSTS_N_INSNS (2); + + if (speed) + *cost += extra_cost->alu.clz + extra_cost->alu.rev; + return false; + case COMPARE: op0 = XEXP (x, 0); op1 = XEXP (x, 1); diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 18d643485d6..1153c742ceb 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2020-02-12 Wilco Dijkstra + + PR rtl-optimization/93565 + * gcc.target/aarch64/pr93565.c: New test. + 2020-02-12 Wilco Dijkstra * gcc.target/aarch64/popcnt2.c: New test. diff --git a/gcc/testsuite/gcc.target/aarch64/pr93565.c b/gcc/testsuite/gcc.target/aarch64/pr93565.c new file mode 100644 index 00000000000..7200f80d1bb --- /dev/null +++ b/gcc/testsuite/gcc.target/aarch64/pr93565.c @@ -0,0 +1,34 @@ +/* { dg-do compile } */ +/* { dg-options "-O2" } */ + +static const unsigned long long magic = 0x03f08c5392f756cdULL; + +static const char table[64] = { + 0, 1, 12, 2, 13, 22, 17, 3, + 14, 33, 23, 36, 18, 58, 28, 4, + 62, 15, 34, 26, 24, 48, 50, 37, + 19, 55, 59, 52, 29, 44, 39, 5, + 63, 11, 21, 16, 32, 35, 57, 27, + 61, 25, 47, 49, 54, 51, 43, 38, + 10, 20, 31, 56, 60, 46, 53, 42, + 9, 30, 45, 41, 8, 40, 7, 6, +}; + +static inline int ctz1 (unsigned long b) +{ + unsigned long lsb = b & -b; + return table[(lsb * magic) >> 58]; +} + +void f (unsigned long x, int *p) +{ + if (x != 0) + { + int a = ctz1 (x); + *p = a | p[a]; + } +} + +/* { dg-final { scan-assembler-times "rbit\t" 1 } } */ +/* { dg-final { scan-assembler-times "clz\t" 1 } } */ + -- 2.30.2