Fold comparisons against a constant nan, and optimize ORD/UNORD

comparisons with a constant.  This allows us to compile isnan to:

_foo:
	fcmpu cr7, f1, f1
	mfcr r2
	rlwinm r3, r2, 0, 31, 31
	blr 

instead of:

LCPI1_0:					;  float
	.space	4
_foo:
	lis r2, ha16(LCPI1_0)
	lfs f0, lo16(LCPI1_0)(r2)
	fcmpu cr7, f1, f0
	mfcr r2
	rlwinm r3, r2, 0, 31, 31
	blr 

llvm-svn: 45405

1 files changed, 0 insertions, 17 deletions

diff --git a/llvm/lib/Target/X86/README.txt b/llvm/lib/Target/X86/README.txt
index 08b5875c574..759c7acf389 100644
--- a/llvm/lib/Target/X86/README.txt
+++ b/llvm/lib/Target/X86/README.txt
@@ -816,23 +816,6 @@ _add_zf:
 
 //===---------------------------------------------------------------------===//
 
-This:
-#include <math.h>
-int foo(double X) { return isnan(X); }
-
-compiles to (-m64):
-
-_foo:
-        pxor %xmm1, %xmm1
-        ucomisd %xmm1, %xmm0
-        setp %al
-        movzbl %al, %eax
-        ret
-
-the pxor is not needed, we could compare the value against itself.
-
-//===---------------------------------------------------------------------===//
-
 These two functions have identical effects:
 
 unsigned int f(unsigned int i, unsigned int n) {++i; if (i == n) ++i; return i;}