parisc: avoid undefined shift in cnv_float.h

The attached change fixes a float conversion problem found running the
GCC testsuite with GCC configured with --with-arch=2.0.

The actual problem occurs for an exponent value of 63. This is the
maximum exponent value that can be passed. This causes a left shift by
32 in the else hunk of the macro. This causes undefined behavior and the
wrong value is returned for dresultB. The fix is the check "exponent <=
62". If the exponent is 63, dresultB is set to 0. The patch also
optimizes the operation a bit by copying "Sall(sgl_value) <<
SGL_EXP_LENGTH" to val, so that sgl_value is not modified.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>

1 files changed, 5 insertions, 6 deletions

diff --git a/arch/parisc/math-emu/cnv_float.h b/arch/parisc/math-emu/cnv_float.h
index 9071e093164a..933423fa5144 100644
--- a/arch/parisc/math-emu/cnv_float.h
+++ b/arch/parisc/math-emu/cnv_float.h
@@ -347,16 +347,15 @@
     Sgl_isinexact_to_fix(sgl_value,exponent)
 
 #define Duint_from_sgl_mantissa(sgl_value,exponent,dresultA,dresultB)   \
-  {Sall(sgl_value) <<= SGL_EXP_LENGTH;  /*  left-justify  */            \
+  {unsigned int val = Sall(sgl_value) << SGL_EXP_LENGTH;                \
     if (exponent <= 31) {                                               \
-        Dintp1(dresultA) = 0;                                           \
-        Dintp2(dresultB) = (unsigned)Sall(sgl_value) >> (31 - exponent); \
+        Dintp1(dresultA) = 0;                                           \
+        Dintp2(dresultB) = val >> (31 - exponent);                      \
     }                                                                   \
     else {                                                              \
-        Dintp1(dresultA) = Sall(sgl_value) >> (63 - exponent);          \
-        Dintp2(dresultB) = Sall(sgl_value) << (exponent - 31);          \
+        Dintp1(dresultA) = val >> (63 - exponent);                      \
+        Dintp2(dresultB) = exponent <= 62 ? val << (exponent - 31) : 0; \
     }                                                                   \
-    Sall(sgl_value) >>= SGL_EXP_LENGTH;  /* return to original */       \
   }
 
 #define Duint_setzero(dresultA,dresultB)        \