slackcoder/qemu - QEMU is a generic and open source machine & userspace emulator and virtualizer

Age	Commit message (Collapse)	Author
2022-03-05	tests/tcg/ppc64le: emit bcdsub with .long when needed	Matheus Ferst
	Based on GCC docs[1], we use the '-mpower8-vector' flag at config-time to detect the toolchain support to the bcdsub instruction. LLVM/Clang supports this flag since version 3.6[2], but the instruction and related builtins were only added in LLVM 14[3]. In the absence of other means to detect this support at config-time, we resort to __has_builtin to identify the presence of __builtin_bcdsub at compile-time. If the builtin is not available, the instruction is emitted with a ".long". [1] https://gcc.gnu.org/onlinedocs/gcc-8.3.0/gcc/PowerPC-AltiVec_002fVSX-Built-in-Functions.html [2] https://github.com/llvm/llvm-project/commit/59eb767e11d4ffefb5f55409524e5c8416b2b0db [3] https://github.com/llvm/llvm-project/commit/c933c2eb334660c131f4afc9d194fafb0cec0423 Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br> Message-Id: <20220304165417.1981159-5-matheus.ferst@eldorado.org.br> Signed-off-by: Cédric Le Goater <clg@kaod.org>
2022-03-05	tests/tcg/ppc64le: drop __int128 usage in bcdsub	Matheus Ferst
	Using __int128 with inline asm constraints like "v" generates incorrect code when compiling with LLVM/Clang (e.g., only one doubleword of the VSR is loaded). Instead, use a GPR pair to pass the 128-bits value and load the VSR with mtvsrd/xxmrghd. Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br> Message-Id: <20220304165417.1981159-4-matheus.ferst@eldorado.org.br> Signed-off-by: Cédric Le Goater <clg@kaod.org>
2021-03-10	target/ppc: Fix bcdsub. emulation when result overflows	Fabiano Rosas
	The commit d03b174a83 (target/ppc: simplify bcdadd/sub functions) meant to simplify some of the code but it inadvertently altered the way the CR6 field is set after the operation has overflowed. The CR6 bits are set based on the unbounded result of the operation, so we need to look at the result before returning from bcd_add_mag, otherwise we will look at 0 when it overflows. Consider the following subtraction: v0 = 0x9999999999999999999999999999999c (maximum positive BCD value) v1 = 0x0000000000000000000000000000001d (negative one BCD value) bcdsub. v0,v0,v1,0 The Power ISA 2.07B says: If the unbounded result is greater than zero, do the following. If PS=0, the sign code of the result is set to 0b1100. If PS=1, the sign code of the result is set to 0b1111. If the operation overflows, CR field 6 is set to 0b0101. Otherwise, CR field 6 is set to 0b0100. POWER9 hardware: vr0 = 0x0000000000000000000000000000000c (positive zero BCD value) cr6 = 0b0101 (0x5) (positive, overflow) QEMU: vr0 = 0x0000000000000000000000000000000c (positive zero BCD value) cr6 = 0b0011 (0x3) (zero, overflow) <--- wrong This patch reverts the part of d03b174a83 that introduced the problem and adds a test-case to avoid further regressions: before: $ make run-tcg-tests-ppc64le-linux-user (...) TEST bcdsub on ppc64le bcdsub: qemu/tests/tcg/ppc64le/bcdsub.c:58: test_bcdsub_gt: Assertion `(cr >> 4) == ((1 << 2) \| (1 << 0))' failed. Fixes: d03b174a83 (target/ppc: simplify bcdadd/sub functions) Reported-by: Paul Clarke <pc@us.ibm.com> Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com> Message-Id: <20210222194035.2723056-1-farosas@linux.ibm.com> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>