Re: [PATCH 3/6] powerpc sstep: Add cnttzw, cnttzd instruction emulation

On Mon, Sep 03, 2018 at 08:49:35PM +0530, Sandipan Das wrote:

+		case 538:	/* cnttzw */
+			if (!cpu_has_feature(CPU_FTR_ARCH_300))
+				return -1;
+			val = (unsigned int) regs->gpr[rd];
+			op->val = ( val ? __builtin_ctz(val) : 32 );
+			goto logical_done;
+#ifdef __powerpc64__
+		case 570:	/* cnttzd */
+			if (!cpu_has_feature(CPU_FTR_ARCH_300))
+				return -1;
+			val = regs->gpr[rd];
+			op->val = ( val ? __builtin_ctzl(val) : 64 );
+			goto logical_done;

__builtin_ctz(val) is undefined for val == 0.


Segher