From: Taylor R Campbell <campbell@mumble.net>
Date: Sat, 22 Feb 2014 22:28:39 +0000 (+0000)
Subject: On i386, avoid FCOM[P] and FTST in favour of FUCOM[P].
X-Git-Tag: release-9.2.0~45
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=521ffb3;p=mit-scheme.git

On i386, avoid FCOM[P] and FTST in favour of FUCOM[P].

The FCOM[P] and FTST instructions trap even on quiet NaN; the
FUCOM[P] instructions don't.
---

diff --git a/src/compiler/machines/i386/rulflo.scm b/src/compiler/machines/i386/rulflo.scm
index 5dc0ab630..ace08312e 100644
--- a/src/compiler/machines/i386/rulflo.scm
+++ b/src/compiler/machines/i386/rulflo.scm
@@ -657,14 +657,14 @@ USA.
 	 (st2 (flonum-source! source2)))
     (cond ((zero? st1)
 	   (flonum-branch! predicate
-			   (LAP (FCOM (ST 0) (ST ,st2)))))
+			   (LAP (FUCOM (ST 0) (ST ,st2)))))
 	  ((zero? st2)
 	   (flonum-branch! (commute-flonum-predicate predicate)
-			   (LAP (FCOM (ST 0) (ST ,st1)))))
+			   (LAP (FUCOM (ST 0) (ST ,st1)))))
 	  (else
 	   (flonum-branch! predicate
 			   (LAP (FLD (ST ,st1))
-				(FCOMP (ST 0) (ST ,(1+ st2)))))))))
+				(FUCOMP (ST 0) (ST ,(1+ st2)))))))))
 
 (define-rule predicate
   (FLONUM-PRED-2-ARGS (? predicate)
@@ -692,18 +692,15 @@ USA.
 
 (define (flonum-compare-zero predicate source)
   (let ((sti (flonum-source! source)))
-    (if (zero? sti)
-	(flonum-branch! predicate
-			(LAP (FTST)))
-	(flonum-branch! (commute-flonum-predicate predicate)
-			(LAP (FLDZ)
-			     (FCOMP (ST 0) (ST ,(1+ sti))))))))
+    (flonum-branch! (commute-flonum-predicate predicate)
+		    (LAP (FLDZ)
+			 (FUCOMP (ST 0) (ST ,(1+ sti)))))))
 
 (define (flonum-compare-one predicate source)
   (let ((sti (flonum-source! source)))
     (flonum-branch! (commute-flonum-predicate predicate)
 		    (LAP (FLD1)
-			 (FCOMP (ST 0) (ST ,(1+ sti)))))))
+			 (FUCOMP (ST 0) (ST ,(1+ sti)))))))
 
 (define (commute-flonum-predicate pred)
   (case pred
diff --git a/src/microcode/cmpauxmd/i386.m4 b/src/microcode/cmpauxmd/i386.m4
index a779873c5..33cf5476c 100644
--- a/src/microcode/cmpauxmd/i386.m4
+++ b/src/microcode/cmpauxmd/i386.m4
@@ -984,7 +984,8 @@ define_hook_label(generic_$1)
 	jne	asm_generic_$1_fail
 	OP(and,l)	TW(rmask,REG(edx))
 	OP(fld,l)	DOF(4,REG(edx))
-	ftst
+	fldz
+	fucomp	ST(1)
 	fstsw	REG(ax)
 	fstp	ST(0)
 	sahf
@@ -1088,7 +1089,8 @@ asm_generic_divide_flo_flo:
 	OP(mov,l)	TW(REG(ebx),REG(ecx))
 	OP(and,l)	TW(rmask,REG(ecx))
 	OP(fld,l)	DOF(4,REG(ecx))			# fldd
-	ftst
+	fldz
+	fucomp	ST(1)
 	fstsw	REG(ax)
 	sahf
 	je	asm_generic_divide_by_zero