MIPS: Improve runtime detection and compatibility wrt arch. revisions.

TEST=
BUG=
R=jkummerow@chromium.org, paul.lind@imgtec.com

Review URL: https://codereview.chromium.org/618193005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24486 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

build/toolchain.gypi

@@ -302,7 +302,7 @@
                     'cflags': ['-mfp32'],
                   }],
                   ['mips_arch_variant=="r6"', {
-                    'cflags!': ['-mfp32'],
+                    'cflags!': ['-mfp32', '-mfpxx'],
                     'cflags': ['-mips32r6', '-Wa,-mips32r6'],
                     'ldflags': [
                       '-mips32r6',
@@ -312,14 +312,17 @@
                   }],
                   ['mips_arch_variant=="r2"', {
                     'cflags': ['-mips32r2', '-Wa,-mips32r2'],
+                    'ldflags': ['-mips32r2'],
                   }],
                   ['mips_arch_variant=="r1"', {
-                    'cflags!': ['-mfp64'],
+                    'cflags!': ['-mfp64', '-mfpxx'],
                     'cflags': ['-mips32', '-Wa,-mips32'],
+                    'ldflags': ['-mips32'],
                   }],
                   ['mips_arch_variant=="rx"', {
-                    'cflags!': ['-mfp64'],
-                    'cflags': ['-mips32', '-Wa,-mips32'],
+                    'cflags!': ['-mfp64', '-mfp32'],
+                    'cflags': ['-mips32', '-Wa,-mips32', '-mfpxx'],
+                    'ldflags': ['-mips32'],
                   }],
                 ],
               }],
@@ -400,7 +403,7 @@
                     'cflags': ['-mfp32'],
                   }],
                   ['mips_arch_variant=="r6"', {
-                    'cflags!': ['-mfp32'],
+                    'cflags!': ['-mfp32', '-mfpxx'],
                     'cflags': ['-mips32r6', '-Wa,-mips32r6'],
                     'ldflags': [
                       '-mips32r6',
@@ -410,17 +413,20 @@
                   }],
                   ['mips_arch_variant=="r2"', {
                     'cflags': ['-mips32r2', '-Wa,-mips32r2'],
+                    'ldflags': ['-mips32r2'],
                   }],
                   ['mips_arch_variant=="r1"', {
-                    'cflags!': ['-mfp64'],
+                    'cflags!': ['-mfp64', '-mfpxx'],
                     'cflags': ['-mips32', '-Wa,-mips32'],
+                    'ldflags': ['-mips32'],
                   }],
                   ['mips_arch_variant=="rx"', {
-                    'cflags!': ['-mfp64'],
-                    'cflags': ['-mips32', '-Wa,-mips32'],
+                    'cflags!': ['-mfp64', '-mfp32'],
+                    'cflags': ['-mips32', '-Wa,-mips32', '-mfpxx'],
+                    'ldflags': ['-mips32'],
                   }],
                   ['mips_arch_variant=="loongson"', {
-                    'cflags!': ['-mfp64'],
+                    'cflags!': ['-mfp64', '-mfp32', '-mfpxx'],
                     'cflags': ['-mips3', '-Wa,-mips3'],
                   }],
                 ],

src/base/cpu.cc

@@ -121,13 +121,18 @@ static uint32_t ReadELFHWCaps() {
 int __detect_fp64_mode(void) {
   double result = 0;
   // Bit representation of (double)1 is 0x3FF0000000000000.
-  asm(
+  __asm__ volatile(
+      ".set push\n\t"
+      ".set noreorder\n\t"
+      ".set oddspreg\n\t"
       "lui $t0, 0x3FF0\n\t"
       "ldc1 $f0, %0\n\t"
       "mtc1 $t0, $f1\n\t"
       "sdc1 $f0, %0\n\t"
-    : "+m" (result)
-    : : "t0", "$f0", "$f1", "memory");
+      ".set pop\n\t"
+      : "+m"(result)
+      :
+      : "t0", "$f0", "$f1", "memory");
 
   return !(result == 1);
 }
@@ -135,9 +140,22 @@ int __detect_fp64_mode(void) {
 
 int __detect_mips_arch_revision(void) {
   // TODO(dusmil): Do the specific syscall as soon as it is implemented in mips
-  // kernel. Currently fail-back to the least common denominator which is
-  // mips32 revision 1.
-  return 1;
+  // kernel.
+  uint32_t result = 0;
+  __asm__ volatile(
+      "move $v0, $zero\n\t"
+      // Encoding for "addi $v0, $v0, 1" on non-r6,
+      // which is encoding for "bovc $v0, %v0, 1" on r6.
+      // Use machine code directly to avoid compilation errors with different
+      // toolchains and maintain compatibility.
+      ".word 0x20420001\n\t"
+      "sw $v0, %0\n\t"
+      : "=m"(result)
+      :
+      : "v0", "memory");
+  // Result is 0 on r6 architectures, 1 on other architecture revisions.
+  // Fall-back to the least common denominator which is mips32 revision 1.
+  return result ? 1 : 6;
 }
 #endif
 

src/mips/constants-mips.h

@@ -105,7 +105,7 @@ const uint32_t kHoleNanLower32Offset = 4;
   (kArchVariant == check)
 #else
 #define IsMipsArchVariant(check) \
-  (CpuFeatures::IsSupported(check))
+  (CpuFeatures::IsSupported(static_cast<CpuFeature>(check)))
 #endif