[RISC-V] [PATCH v2] Enable inlining str* by default

So with Chrstoph's patches from late 2022 we've had the ability to inline
strlen, and str[n]cmp (scalar).  However, we never actually turned this
capability on by default!

This patch flips the those default to allow inlinining by default.  It also
fixes one bug exposed by our internal testing when NBYTES is zero for strncmp.
I don't think that case happens enough to try and optimize it, we just disable
inline expansion for that instance.

This has been bootstrapped and regression tested on rv64gc at various times as
well as cross tested on rv64gc more times than I can probably count (we've have
this patch internally for a while).  More importantly, I just successfully
tested it on rv64gc and rv32gcv elf configurations with the trunk

gcc/

	* config/riscv/riscv-string.cc (riscv_expand_strcmp): Do not inline
	strncmp with zero size.
	(emit_strcmp_scalar_compare_subword): Adjust rotation for rv32 vs rv64.
	* config/riscv/riscv.opt (var_inline_strcmp): Enable by default.
	(vriscv_inline_strncmp, riscv_inline_strlen): Likewise.

gcc/testsuite

	* gcc.target/riscv/zbb-strlen-disabled-2.c: Turn off inlining.

diff --git a/gcc/config/riscv/riscv-string.cc b/gcc/config/riscv/riscv-string.cc
index b09b51d7526b9085cdd20706d10f95ecff91db69..41cb061c746d43d4aaf9500a395fd3a32c2ddc00 100644 (file)
--- a/gcc/config/riscv/riscv-string.cc
+++ b/gcc/config/riscv/riscv-string.cc
@@ -153,7 +153,7 @@ emit_strcmp_scalar_compare_subword (rtx data1, rtx data2, rtx orc1,
   rtx imask = gen_rtx_CONST_INT (Xmode, im);
   rtx m_reg = gen_reg_rtx (Xmode);
   emit_insn (gen_rtx_SET (m_reg, imask));
-  do_rotr3 (m_reg, m_reg, GEN_INT (64 - cmp_bytes * BITS_PER_UNIT));
+  do_rotr3 (m_reg, m_reg, GEN_INT (BITS_PER_WORD - cmp_bytes * BITS_PER_UNIT));
   do_and3 (data1, m_reg, data1);
   do_and3 (data2, m_reg, data2);
   if (TARGET_ZBB)
@@ -497,6 +497,13 @@ riscv_expand_strcmp (rtx result, rtx src1, rtx src2,
        return false;
       nbytes = UINTVAL (bytes_rtx);
 
+      /* If NBYTES is zero the result of strncmp will always be zero,
+        but that would require special casing in the caller.  So for
+        now just don't do an inline expansion.  This probably rarely
+        happens in practice, but it is tested by the testsuite.  */
+      if (nbytes == 0)
+       return false;
+
       /* We don't emit parts of a strncmp() call.  */
       if (nbytes > compare_max)
        return false;

diff --git a/gcc/config/riscv/riscv.opt b/gcc/config/riscv/riscv.opt
index 7cca1c4aab200e825ef1fc8d6026fbd1fecac353..1252834aec5bf44b5da4cc9ca44c27fd7a88c8c3 100644 (file)
--- a/gcc/config/riscv/riscv.opt
+++ b/gcc/config/riscv/riscv.opt
@@ -517,15 +517,15 @@ Target Var(TARGET_INLINE_SUBWORD_ATOMIC) Init(1)
 Always inline subword atomic operations.
 
 minline-strcmp
-Target Var(riscv_inline_strcmp) Init(0)
+Target Var(riscv_inline_strcmp) Init(1)
 Inline strcmp calls if possible.
 
 minline-strncmp
-Target Var(riscv_inline_strncmp) Init(0)
+Target Var(riscv_inline_strncmp) Init(1)
 Inline strncmp calls if possible.
 
 minline-strlen
-Target Var(riscv_inline_strlen) Init(0)
+Target Var(riscv_inline_strlen) Init(1)
 Inline strlen calls if possible.
 
 -param=riscv-strcmp-inline-limit=

diff --git a/gcc/testsuite/gcc.target/riscv/zbb-strlen-disabled-2.c b/gcc/testsuite/gcc.target/riscv/zbb-strlen-disabled-2.c
index a481068aa0c7714976253fdf0c7a4986e36a19b9..1295aeb0086e336522835fff488c82ba1384e78e 100644 (file)
--- a/gcc/testsuite/gcc.target/riscv/zbb-strlen-disabled-2.c
+++ b/gcc/testsuite/gcc.target/riscv/zbb-strlen-disabled-2.c
@@ -1,6 +1,6 @@
 /* { dg-do compile } */
-/* { dg-options "-march=rv32gc_zbb" { target { rv32 } } } */
-/* { dg-options "-march=rv64gc_zbb" { target { rv64 } } } */
+/* { dg-options "-mno-inline-strlen -march=rv32gc_zbb" { target { rv32 } } } */
+/* { dg-options "-mno-inline-strlen -march=rv64gc_zbb" { target { rv64 } } } */
 /* { dg-skip-if "" { *-*-* } { "-O0" "-Os" "-Og" "-Oz" } } */
 
 typedef long unsigned int size_t;