cpu: add gccgo implementation
It uses __get_cpuid_count, provided by cpuid.h.
The xgetbv is implemented after its counterpart in cpu_x86.s.
Change-Id: I97624d7da67ab4ec3c9a53b0bfc4dfcdf7d12c87
Reviewed-on: https://go-review.googlesource.com/116155
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/cpu/cpu_gccgo.c b/cpu/cpu_gccgo.c
new file mode 100644
index 0000000..e363c7d
--- /dev/null
+++ b/cpu/cpu_gccgo.c
@@ -0,0 +1,43 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build 386 amd64 amd64p32
+// +build gccgo
+
+#include <cpuid.h>
+#include <stdint.h>
+
+// Need to wrap __get_cpuid_count because it's declared as static.
+int
+gccgoGetCpuidCount(uint32_t leaf, uint32_t subleaf,
+ uint32_t *eax, uint32_t *ebx,
+ uint32_t *ecx, uint32_t *edx)
+{
+ return __get_cpuid_count(leaf, subleaf, eax, ebx, ecx, edx);
+}
+
+// xgetbv reads the contents of an XCR (Extended Control Register)
+// specified in the ECX register into registers EDX:EAX.
+// Currently, the only supported value for XCR is 0.
+//
+// TODO: Replace with a better alternative:
+//
+// #include <xsaveintrin.h>
+//
+// #pragma GCC target("xsave")
+//
+// void gccgoXgetbv(uint32_t *eax, uint32_t *edx) {
+// unsigned long long x = _xgetbv(0);
+// *eax = x & 0xffffffff;
+// *edx = (x >> 32) & 0xffffffff;
+// }
+//
+// Note that _xgetbv is defined starting with GCC 8.
+void
+gccgoXgetbv(uint32_t *eax, uint32_t *edx)
+{
+ __asm(" xorl %%ecx, %%ecx\n"
+ " xgetbv"
+ : "=a"(*eax), "=d"(*edx));
+}
