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This is an incomplete proof of concept that I applied to be able to
build a 64 bit kernel with GCC-4.4. It doesn't handle the 32 bit case
or the R4000_WAR case.
Comments welcome.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
---
arch/mips/include/asm/compiler.h | 7 +++++++
arch/mips/include/asm/delay.h | 4 ++++
2 files changed, 11 insertions(+), 0 deletions(-)
--- a/arch/mips/include/asm/compiler.h
+++ b/arch/mips/include/asm/compiler.h
@@ -26,4 +26,11 @@ typedef u64 uintx_t;
#endif
#endif
+#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4)
+#define GCC_NO_H_CONSTRAINT
+#ifdef CONFIG_64BIT
+typedef unsigned int uint128_t __attribute__((mode(TI)));
+#endif
+#endif
+
#endif /* _ASM_COMPILER_H */
--- a/arch/mips/include/asm/delay.h
+++ b/arch/mips/include/asm/delay.h
@@ -67,10 +67,14 @@ static inline unsigned long __usecs_to_l
: "r" (usecs), "r" (lpj)
: GCC_REG_ACCUM);
else if (sizeof(long) == 8 && !R4000_WAR)
+#ifdef GCC_NO_H_CONSTRAINT
+ usecs = ((uint128_t)usecs * lpj) >> 64;
+#else
__asm__("dmultu\t%2, %3"
: "=h" (usecs), "=l" (lo)
: "r" (usecs), "r" (lpj)
: GCC_REG_ACCUM);
+#endif
else if (sizeof(long) == 8 && R4000_WAR)
__asm__("dmultu\t%3, %4\n\tmfhi\t%0"
: "=r" (usecs), "=h" (hi), "=l" (lo)
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