Before I commit this, or do the corresponding tree level patch, I would
like this to be looked at by the FP people. I am guessing at some of
this, other parts i gleaned from various standards docs and an irc
conversation with Joseph. This should have been documented when it was
put into the compiler. This is certainly not obvious.
Kenny
Index: gcc/doc/rtl.texi
===================================================================
--- gcc/doc/rtl.texi (revision 220541)
+++ gcc/doc/rtl.texi (working copy)
@@ -2553,40 +2553,52 @@ of comparisons is supported on a particu
pass will try to merge the operations to produce the @code{eq} shown
in case it exists in the context of the particular insn involved.
-Inequality comparisons come in two flavors, signed and unsigned. Thus,
-there are distinct expression codes @code{gt} and @code{gtu} for signed and
-unsigned greater-than. These can produce different results for the same
-pair of integer values: for example, 1 is signed greater-than @minus{}1 but not
-unsigned greater-than, because @minus{}1 when regarded as unsigned is actually
+Fixed point inequality comparisons come in two flavors, signed and
+unsigned. Thus, there are distinct expression codes @code{gt} and
+@code{gtu} for signed and unsigned greater-than. These can produce
+different results for the same pair of integer values: for example, 1
+is signed greater-than @minus{}1 but not unsigned greater-than,
+because @minus{}1 when regarded as unsigned is actually
@code{0xffffffff} which is greater than 1.
-The signed comparisons are also used for floating point values. Floating
-point comparisons are distinguished by the machine modes of the operands.
+Floating point comparisons come in two flavors, signaling and quiet,
+though these are not always paired. The fixed point signed
+comparisons are also used for floating point comparisons. Floating
+point comparisons are distinguished by the machine modes of the
+operands.
@table @code
@findex eq
@cindex equal
@item (eq:@var{m} @var{x} @var{y})
-@code{STORE_FLAG_VALUE} if the values represented by @var{x} and @var{y}
-are equal, otherwise 0.
+@code{STORE_FLAG_VALUE} if the values represented by @var{x} and
+@var{y} are equal, otherwise 0. If the operands are floating point,
+this is a quiet comparison and corresponds to the IEC 60559
+@code{compareQuietEqual} operation.
@findex ne
@cindex not equal
@item (ne:@var{m} @var{x} @var{y})
-@code{STORE_FLAG_VALUE} if the values represented by @var{x} and @var{y}
-are not equal, otherwise 0.
+@code{STORE_FLAG_VALUE} if the values represented by @var{x} and
+@var{y} are not equal, otherwise 0. If the operands are floating
+point, this is a quiet comparison and corresponds to the IEC 60559
+@code{compareQuietNotEqual} operation.
@findex gt
@cindex greater than
@item (gt:@var{m} @var{x} @var{y})
-@code{STORE_FLAG_VALUE} if the @var{x} is greater than @var{y}. If they
-are fixed-point, the comparison is done in a signed sense.
+@code{STORE_FLAG_VALUE} if the @var{x} is greater than @var{y}. If
+the operands are fixed-point, the comparison is done in a signed
+sense. If the operands are floating point, this is a signaling
+comparison and corresponds to the IEC 60559
+@code{compareSignalingGreater} operation.
@findex gtu
@cindex greater than
@cindex unsigned greater than
@item (gtu:@var{m} @var{x} @var{y})
-Like @code{gt} but does unsigned comparison, on fixed-point numbers only.
+Like @code{gt} but does unsigned comparison, on fixed-point numbers
+only. This is undefined for floating point numbers.
@findex lt
@cindex less than
@@ -2594,7 +2606,10 @@ Like @code{gt} but does unsigned compari
@cindex unsigned less than
@item (lt:@var{m} @var{x} @var{y})
@itemx (ltu:@var{m} @var{x} @var{y})
-Like @code{gt} and @code{gtu} but test for ``less than''.
+Like @code{gt} and @code{gtu} but test for ``less than''. If the
+operands are floating point, @code{gt} is a signaling comparison and
+corresponds to the IEC 60559 @code{compareSignalingLess} operation.
+@code{gtu} is undefined for floating point numbers.
@findex ge
@cindex greater than
@@ -2603,6 +2618,10 @@ Like @code{gt} and @code{gtu} but test f
@item (ge:@var{m} @var{x} @var{y})
@itemx (geu:@var{m} @var{x} @var{y})
Like @code{gt} and @code{gtu} but test for ``greater than or equal''.
+If the operands are floating point, @code{ge} is a signaling
+comparison and corresponds to the IEC 60559
+@code{compareSignalingGreater} operation. @code{geu} is undefined for
+floating point numbers.
@findex le
@cindex less than or equal
@@ -2610,7 +2629,64 @@ Like @code{gt} and @code{gtu} but test f
@cindex unsigned less than
@item (le:@var{m} @var{x} @var{y})
@itemx (leu:@var{m} @var{x} @var{y})
-Like @code{gt} and @code{gtu} but test for ``less than or equal''.
+Like @code{gt} and @code{gtu} but test for ``less than or equal''. If
+the operands are floating point, @code{le} is a signaling comparison
+and corresponds to the IEC 60559 @code{compareSignalingLess}
+operation. @code{leu} is undefined for floating point numbers.
+
+@table @code
+@findex unlt
+@cindex unordered less than
+@item (unlt:@var{m} @var{x} @var{y})
+@code{STORE_FLAG_VALUE} if the values represented by @var{x} and
+@var{y} are less or unordered, otherwise 0. This is a quiet operation
+that applies only to floating point operands and corresponds to the
+IEC 60559 @code{compareQuietLessUnordered} operation.
+
+@table @code
+@findex unle
+@cindex unordered less equal
+@item (unle:@var{m} @var{x} @var{y})
+@code{STORE_FLAG_VALUE} if the values represented by @var{x} and
+@var{y} are less, equal, or unordered, otherwise 0. This is a quiet
+operation that applies only to floating point operands and corresponds
+to the IEC 60559 @code{compareQuietNotGreater} operation.
+
+@table @code
+@findex ltgt
+@cindex less than or greater than
+@item (ltgt:@var{m} @var{x} @var{y})
+@code{STORE_FLAG_VALUE} if the values represented by @var{x} and
+@var{y} are less, or greater, otherwise 0. This is a quiet operation
+that applies only to floating point operands and does not have a
+corresponding IEC 60559 operation.
+
+@table @code
+@findex uneq
+@cindex unordered or equal
+@item (uneq:@var{m} @var{x} @var{y})
+@code{STORE_FLAG_VALUE} if the values represented by @var{x} and
+@var{y} are unordered or equal, otherwise 0. This is a quiet
+operation that applies only to floating point operands and does not
+have a corresponding IEC 60559 operation.
+
+@table @code
+@findex ordered
+@cindex less equal or greater
+@item (ordered:@var{m} @var{x} @var{y})
+@code{STORE_FLAG_VALUE} if the values represented by both @var{x} and
+@var{y} are not nan, otherwise 0. This is a quiet operation that
+applies only to floating point operands and corresponds to the IEC
+60559 @code{compareQuietOrdered} operation.
+
+@table @code
+@findex unordered
+@cindex is a nan
+@item (unordered:@var{m} @var{x} @var{y})
+@code{STORE_FLAG_VALUE} if the values represented by either @var{x}
+and either @var{y} are nan, otherwise 0. This is a quiet operation
+that applies only to floating point operands and corresponds to the
+IEC 60559 @code{compareQuietUnordered} operation.
@findex if_then_else
@item (if_then_else @var{cond} @var{then} @var{else})
