meson: allow configuring the x86-64 baseline

Add a Meson option to configure which x86-64 instruction
set to use.  QEMU will now default to x86-64-v1 + cmpxchg16b for
64-bit builds (that corresponds to a Pentium 4 for 32-bit builds).

The baseline can be tuned down to Pentium Pro for 32-bit builds (with
-Dx86_version=0), or up as desired.

Acked-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

3 files changed, 39 insertions, 8 deletions

diff --git a/meson.build b/meson.build
index 97e00d6..6e694ec 100644
--- a/meson.build
+++ b/meson.build
@@ -336,15 +336,40 @@ if host_arch == 'i386' and not cc.links('''
   qemu_common_flags = ['-march=i486'] + qemu_common_flags
 endif
 
-# Assume x86-64-v2 (minus CMPXCHG16B for 32-bit code)
-if host_arch == 'i386'
-  qemu_common_flags = ['-mfpmath=sse'] + qemu_common_flags
-endif
+# Pick x86-64 baseline version
 if host_arch in ['i386', 'x86_64']
-  qemu_common_flags = ['-mpopcnt', '-msse4.2'] + qemu_common_flags
-endif
-if host_arch == 'x86_64'
-  qemu_common_flags = ['-mcx16'] + qemu_common_flags
+  if get_option('x86_version') == '0' and host_arch == 'x86_64'
+    error('x86_64-v1 required for x86-64 hosts')
+  endif
+
+  # add flags for individual instruction set extensions
+  if get_option('x86_version') >= '1'
+    if host_arch == 'i386'
+      qemu_common_flags = ['-mfpmath=sse'] + qemu_common_flags
+    else
+      # present on basically all processors but technically not part of
+      # x86-64-v1, so only include -mneeded for x86-64 version 2 and above
+      qemu_common_flags = ['-mcx16'] + qemu_common_flags
+    endif
+  endif
+  if get_option('x86_version') >= '2'
+    qemu_common_flags = ['-mpopcnt'] + qemu_common_flags
+    qemu_common_flags = cc.get_supported_arguments('-mneeded') + qemu_common_flags
+  endif
+  if get_option('x86_version') >= '3'
+    qemu_common_flags = ['-mmovbe', '-mabm', '-mbmi1', '-mbmi2', '-mfma', '-mf16c'] + qemu_common_flags
+  endif
+
+  # add required vector instruction set (each level implies those below)
+  if get_option('x86_version') == '1'
+    qemu_common_flags = ['-msse2'] + qemu_common_flags
+  elif get_option('x86_version') == '2'
+    qemu_common_flags = ['-msse4.2'] + qemu_common_flags
+  elif get_option('x86_version') == '3'
+    qemu_common_flags = ['-mavx2'] + qemu_common_flags
+  elif get_option('x86_version') == '4'
+    qemu_common_flags = ['-mavx512f', '-mavx512bw', '-mavx512cd', '-mavx512dq', '-mavx512vl'] + qemu_common_flags
+  endif
 endif
 
 if get_option('prefer_static')
diff --git a/meson_options.txt b/meson_options.txt
index 7a79dd8..6065ed2 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -370,3 +370,6 @@ option('qemu_ga_version', type: 'string', value: '',
 
 option('hexagon_idef_parser', type : 'boolean', value : true,
        description: 'use idef-parser to automatically generate TCG code for the Hexagon frontend')
+
+option('x86_version', type : 'combo', choices : ['0', '1', '2', '3', '4'], value: '1',
+       description: 'tweak required x86_64 architecture version beyond compiler default')
diff --git a/scripts/meson-buildoptions.sh b/scripts/meson-buildoptions.sh
index 58d49a4..62842d4 100644
--- a/scripts/meson-buildoptions.sh
+++ b/scripts/meson-buildoptions.sh
@@ -82,6 +82,8 @@ meson_options_help() {
   printf "%s\n" '  --with-suffix=VALUE      Suffix for QEMU data/modules/config directories'
   printf "%s\n" '                           (can be empty) [qemu]'
   printf "%s\n" '  --with-trace-file=VALUE  Trace file prefix for simple backend [trace]'
+  printf "%s\n" '  --x86-version=CHOICE     tweak required x86_64 architecture version beyond'
+  printf "%s\n" '                           compiler default [1] (choices: 0/1/2/3)'
   printf "%s\n" ''
   printf "%s\n" 'Optional features, enabled with --enable-FEATURE and'
   printf "%s\n" 'disabled with --disable-FEATURE, default is enabled if available'
@@ -552,6 +554,7 @@ _meson_option_parse() {
     --disable-werror) printf "%s" -Dwerror=false ;;
     --enable-whpx) printf "%s" -Dwhpx=enabled ;;
     --disable-whpx) printf "%s" -Dwhpx=disabled ;;
+    --x86-version=*) quote_sh "-Dx86_version=$2" ;;
     --enable-xen) printf "%s" -Dxen=enabled ;;
     --disable-xen) printf "%s" -Dxen=disabled ;;
     --enable-xen-pci-passthrough) printf "%s" -Dxen_pci_passthrough=enabled ;;