From: Evan Shaw <chickencha@gmail.com>
Date: Thu, 7 Jan 2010 03:28:19 +0000 (-0800)
Subject: 8g: float->uint64 conversion optimization
X-Git-Tag: weekly.2010-01-13~54
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=a551ffe809032cce094f10aa2fe5b94bb064f6a4;p=gostls13.git

8g: float->uint64 conversion optimization

Using FUCOMIP instead of the FUCOMP-FSTSW-SAHF sequence gives better performance and saves code space.

R=rsc
CC=golang-dev
https://golang.org/cl/183139
---

diff --git a/src/cmd/8g/gsubr.c b/src/cmd/8g/gsubr.c
index 4625509e9d..2b94824996 100644
--- a/src/cmd/8g/gsubr.c
+++ b/src/cmd/8g/gsubr.c
@@ -1350,15 +1350,11 @@ gmove(Node *f, Node *t)
 
 		// if 0 > v { answer = 0 }
 		gmove(&zerof, &f0);
-		gins(AFUCOMP, &f0, &f1);
-		gins(AFSTSW, N, &ax);
-		gins(ASAHF, N, N);
+		gins(AFUCOMIP, &f0, &f1);
 		p1 = gbranch(optoas(OGT, types[tt]), T);
 		// if 1<<64 <= v { answer = 0 too }
 		gmove(&two64f, &f0);
-		gins(AFUCOMP, &f0, &f1);
-		gins(AFSTSW, N, &ax);
-		gins(ASAHF, N, N);
+		gins(AFUCOMIP, &f0, &f1);
 		p2 = gbranch(optoas(OGT, types[tt]), T);
 		patch(p1, pc);
 		gins(AFMOVVP, &f0, t);	// don't care about t, but will pop the stack
@@ -1382,9 +1378,7 @@ gmove(Node *f, Node *t)
 
 		// actual work
 		gmove(&two63f, &f0);
-		gins(AFUCOMP, &f0, &f1);
-		gins(AFSTSW, N, &ax);
-		gins(ASAHF, N, N);
+		gins(AFUCOMIP, &f0, &f1);
 		p2 = gbranch(optoas(OLE, types[tt]), T);
 		gins(AFMOVVP, &f0, t);
 		p3 = gbranch(AJMP, T);