git: 27e68baf24f1 - stable/13 - Build lib/msun tests with compiler builtins disabled

[Dimitry Andric]

The branch stable/13 has been updated by dim:

URL: https://cgit.FreeBSD.org/src/commit/?id=27e68baf24f1eb10f1cfb48731d7447a78b278ff

commit 27e68baf24f1eb10f1cfb48731d7447a78b278ff
Author:     Dimitry Andric <dim at FreeBSD.org>
AuthorDate: 2021-02-23 20:03:32 +0000
Commit:     Dimitry Andric <dim at FreeBSD.org>
CommitDate: 2021-03-09 20:17:10 +0000

    Build lib/msun tests with compiler builtins disabled
    
    This forces the compiler to emit calls to libm functions, instead of
    possibly substituting pre-calculated results at compile time, which
    should help to actually test those functions.
    
    Reviewed by:    emaste, arichardson, ngie
    Differential Revision: https://reviews.freebsd.org/D28577
    
    (cherry picked from commit cf97d2a1dab8f2cddc4466fe64d37818339c73be)
    
    riscv: Add a soft-float implementation of fabs()
    
    We could just use a C implementation using __builtin_fabs(), but using
    this assembly version guarantees that there is no additional prolog/epilog
    code. Additionally, clang generates worse code for masking off the top bit
    than GCC: https://bugs.llvm.org/show_bug.cgi?id=49377.
    
    This fixes the RISCV64 softfloat world build after cf97d2a1dab8. That commit
    added -fno-builtin to the msun tests which resulted in the first references to
    fabs (previously the compiler inlined all calls).
    
    Reviewed By:    dim
    Reported by:    mjg
    Differential Revision: https://reviews.freebsd.org/D28994
    
    (cherry picked from commit 524b018d200408bed5eb0d2b892db5b9fb46808b)
    
    riscv: Fix whitespace issues in fabs added in 524b018d2004
    
    (cherry picked from commit 066dab17e7a4a78d43dbcef8119960ddc8090a73)
---
 lib/libc/riscv/gen/fabs.S | 11 +++++++++--
 lib/msun/tests/Makefile   |  4 ++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/lib/libc/riscv/gen/fabs.S b/lib/libc/riscv/gen/fabs.S
index 44249252e9c1..036d50eddf90 100644
--- a/lib/libc/riscv/gen/fabs.S
+++ b/lib/libc/riscv/gen/fabs.S
@@ -1,5 +1,6 @@
 /*-
  * Copyright (c) 2015-2017 Ruslan Bukin <br at bsdpad.com>
+ * Copyright (c) 2021 Alex Richardson <arichardson at FreeBSD.org>
  * All rights reserved.
  *
  * Portions of this software were developed by SRI International and the
@@ -10,6 +11,9 @@
  * Computer Laboratory as part of the CTSRD Project, with support from the
  * UK Higher Education Innovation Fund (HEIF).
  *
+ * This work was supported by Innovate UK project 105694, "Digital Security
+ * by Design (DSbD) Technology Platform Prototype".
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ -35,9 +39,12 @@
 #include <machine/asm.h>
 __FBSDID("$FreeBSD$");
 
-#ifdef __riscv_float_abi_double
 ENTRY(fabs)
+#ifdef __riscv_float_abi_double
 	fabs.d	fa0, fa0
+#else
+	slli	a0, a0, 1
+	srli	a0, a0, 1
+#endif
 	ret
 END(fabs)
-#endif
diff --git a/lib/msun/tests/Makefile b/lib/msun/tests/Makefile
index 67a38855309e..902d1ca22f73 100644
--- a/lib/msun/tests/Makefile
+++ b/lib/msun/tests/Makefile
@@ -19,6 +19,10 @@ CFLAGS+=	-I${TESTSRC:H}/libc/gen
 CFLAGS+=	-D__HAVE_LONG_DOUBLE
 .endif
 
+# Avoid builtins, to force the compiler to emit calls to the libm
+# functions, and not calculate any results in advance.
+CFLAGS+=        -fno-builtin
+
 NETBSD_ATF_TESTS_C=	acos_test
 NETBSD_ATF_TESTS_C+=	asin_test
 NETBSD_ATF_TESTS_C+=	atan_test