target-i386: fix {min,max}{pd,ps,sd,ss} SSE2 instructions

minpd, minps, minsd, minss and maxpd, maxps, maxsd, maxss SSE2
instructions have been broken when switching target-i386 to softfloat.
It's not possible to use comparison instructions on float types anymore
to softfloat, so use the floatXX_lt function instead, as the
float_XX_min and float_XX_max functions can't be used due to the Intel
specific behaviour.

As it implements the correct NaNs behaviour, let's remove the
corresponding entry from the TODO.

It fixes GDM screen display on Debian Lenny.

Thanks to Peter Maydell and Jason Wessel for their analysis of the
problem.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

1 files changed, 7 insertions, 2 deletions

diff --git a/target-i386/ops_sse.h b/target-i386/ops_sse.h
index 47dde78f89..8ed231d554 100644
--- a/target-i386/ops_sse.h
+++ b/target-i386/ops_sse.h
@@ -584,10 +584,15 @@ void helper_ ## name ## sd (Reg *d, Reg *s)\
 #define FPU_SUB(size, a, b) float ## size ## _sub(a, b, &env->sse_status)
 #define FPU_MUL(size, a, b) float ## size ## _mul(a, b, &env->sse_status)
 #define FPU_DIV(size, a, b) float ## size ## _div(a, b, &env->sse_status)
-#define FPU_MIN(size, a, b) (a) < (b) ? (a) : (b)
-#define FPU_MAX(size, a, b) (a) > (b) ? (a) : (b)
 #define FPU_SQRT(size, a, b) float ## size ## _sqrt(b, &env->sse_status)
 
+/* Note that the choice of comparison op here is important to get the
+ * special cases right: for min and max Intel specifies that (-0,0),
+ * (NaN, anything) and (anything, NaN) return the second argument.
+ */
+#define FPU_MIN(size, a, b) float ## size ## _lt(a, b, &env->sse_status) ? (a) : (b)
+#define FPU_MAX(size, a, b) float ## size ## _lt(b, a, &env->sse_status) ? (a) : (b)
+
 SSE_HELPER_S(add, FPU_ADD)
 SSE_HELPER_S(sub, FPU_SUB)
 SSE_HELPER_S(mul, FPU_MUL)