Fix for gcc opt bug described in bug 24892. JSRef build fix only, mozilla build still needs some lovin'.

r=rogerl

js/src/config/Linux_All.mk

@@ -50,6 +50,18 @@ CPU_ARCH = $(shell uname -m)
 ifeq (86,$(findstring 86,$(CPU_ARCH)))
 CPU_ARCH = x86
 OS_CFLAGS+= -DX86_LINUX
+
+ifeq (gcc, $(CC))
+# if using gcc on x86, check version for opt bug 
+# (http://bugzilla.mozilla.org/show_bug.cgi?id=24892)
+GCC_VERSION := $(shell gcc -v 2>&1 | grep version | awk '{ print $$3 }')
+GCC_LIST:=$(sort 2.91.66 $(GCC_VERSION) )
+
+ifeq (2.91.66, $(firstword $(GCC_LIST)))
+CFLAGS+= -DGCC_OPT_BUG
+endif
+endif
+
 endif
 GFX_ARCH = x
 
@@ -57,6 +69,7 @@ OS_LIBS = -lm -lc
 
 ASFLAGS += -x assembler-with-cpp
 
+
 ifeq ($(CPU_ARCH),alpha)
 
 # Ask the C compiler on alpha linux to let us work with denormalized

js/src/fdlibm/e_acos.c

@@ -97,7 +97,12 @@ qS4 =  7.70381505559019352791e-02; /* 0x3FB3B8C5, 0xB12E9282 */
 	double x;
 #endif
 {
-	double z,p,q,r,w,s,c,df;
+#ifdef GCC_OPT_BUG
+        volatile double df;
+#else
+        double df;
+#endif
+	double z,p,q,r,w,s,c;
 	int hx,ix;
 	hx = __HI(x);
 	ix = hx&0x7fffffff;

js/src/fdlibm/e_asin.c

@@ -106,7 +106,12 @@ qS4 =  7.70381505559019352791e-02; /* 0x3FB3B8C5, 0xB12E9282 */
 	double x;
 #endif
 {
-	double t,w,p,q,c,r,s;
+#ifdef GCC_OPT_BUG
+        volatile double w;
+#else
+        double w;
+#endif
+	double t,p,q,c,r,s;
 	int hx,ix;
 	hx = __HI(x);
 	ix = hx&0x7fffffff;

js/src/fdlibm/e_exp.c

@@ -139,8 +139,13 @@ P5   =  4.13813679705723846039e-08; /* 0x3E663769, 0x72BEA4D0 */
 	double x;
 #endif
 {
+#ifdef GCC_OPT_BUG
+        volatile int xsb;
+#else
+        int xsb;
+#endif
 	double y,hi,lo,c,t;
-	int k,xsb;
+	int k;
 	unsigned hx;
 
 	hx  = __HI(x);	/* high word of x */

js/src/fdlibm/e_pow.c

@@ -135,8 +135,13 @@ ivln2_l  =  1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/
 	double x, y;
 #endif
 {
-	double z,ax,z_h,z_l,p_h,p_l;
-	double y1,t1,t2,r,s,t,u,v,w;
+#ifdef GCC_OPT_BUG
+        volatile double y1,t1,p_h,t,z,ax;
+#else
+        double y1,t1,p_h,t,z,ax;
+#endif
+	double z_h,z_l,p_l;
+	double t2,r,s,u,v,w;
 	int i,j,k,yisint,n;
 	int hx,hy,ix,iy;
 	unsigned lx,ly;
@@ -236,7 +241,12 @@ ivln2_l  =  1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/
 	    __LO(t1) = 0;
 	    t2 = v-(t1-u);
 	} else {
-	    double s2,s_h,s_l,t_h,t_l;
+#ifdef GCC_OPT_BUG
+	    volatile double s_h,t_h;
+#else
+	    double s_h,t_h;
+#endif
+	    double s2,s_l,t_l;
 	    n = 0;
 	/* take care subnormal number */
 	    if(ix<0x00100000)
@@ -296,6 +306,7 @@ ivln2_l  =  1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/
 	z = p_l+p_h;
 	j = __HI(z);
 	i = __LO(z);
+
 	if (j>=0x40900000) {				/* z >= 1024 */
 	    if(((j-0x40900000)|i)!=0)			/* if z > 1024 */
 		return s*really_big*really_big;			/* overflow */