diff --git a/src/cmd/5a/lex.c b/src/cmd/5a/lex.c
index e762f564622..dbee3657f1a 100644
--- a/src/cmd/5a/lex.c
+++ b/src/cmd/5a/lex.c
@@ -364,7 +364,9 @@ struct
 	"MOVWF",		LTYPE3, AMOVWF,
 
 	"LDREX",		LTYPE3, ALDREX,
+	"LDREXD",		LTYPE3, ALDREXD,
 	"STREX",		LTYPE9, ASTREX,
+	"STREXD",		LTYPE9, ASTREXD,
 
 /*
 	"ABSF",		LTYPEI, AABSF,
diff --git a/src/cmd/5l/5.out.h b/src/cmd/5l/5.out.h
index a25c0f71d33..002b46d451b 100644
--- a/src/cmd/5l/5.out.h
+++ b/src/cmd/5l/5.out.h
@@ -179,6 +179,9 @@ enum	as
 
 	ALDREX,
 	ASTREX,
+	
+	ALDREXD,
+	ASTREXD,
 
 	ALAST,
 };
diff --git a/src/cmd/5l/asm.c b/src/cmd/5l/asm.c
index adc4ae7478c..af6d1dfda06 100644
--- a/src/cmd/5l/asm.c
+++ b/src/cmd/5l/asm.c
@@ -1463,7 +1463,7 @@ if(debug['G']) print("%ux: %s: arm %d %d %d\n", (uint32)(p->pc), p->from.sym->na
 		aclass(&p->from);
 		if(instoffset != 0)
 			diag("offset must be zero in STREX");
-		o1 = (0x3<<23) | (0xf9<<4);
+		o1 = (0x18<<20) | (0xf90);
 		o1 |= p->from.reg << 16;
 		o1 |= p->reg << 0;
 		o1 |= p->to.reg << 12;
@@ -1553,6 +1553,25 @@ if(debug['G']) print("%ux: %s: arm %d %d %d\n", (uint32)(p->pc), p->from.sym->na
 		o1 = oprrr(ACMP+AEND, p->scond);
 		o1 |= p->from.reg<<16;
 		break;
+	case 91:	/* ldrexd oreg,reg */
+		aclass(&p->from);
+		if(instoffset != 0)
+			diag("offset must be zero in LDREX");
+		o1 = (0x1b<<20) | (0xf9f);
+		o1 |= p->from.reg << 16;
+		o1 |= p->to.reg << 12;
+		o1 |= (p->scond & C_SCOND) << 28;
+		break;
+	case 92:	/* strexd reg,oreg,reg */
+		aclass(&p->from);
+		if(instoffset != 0)
+			diag("offset must be zero in STREX");
+		o1 = (0x1a<<20) | (0xf90);
+		o1 |= p->from.reg << 16;
+		o1 |= p->reg << 0;
+		o1 |= p->to.reg << 12;
+		o1 |= (p->scond & C_SCOND) << 28;
+		break;
 	}
 	
 	out[0] = o1;
diff --git a/src/cmd/5l/optab.c b/src/cmd/5l/optab.c
index 8b3135e06ed..625b6681210 100644
--- a/src/cmd/5l/optab.c
+++ b/src/cmd/5l/optab.c
@@ -253,5 +253,8 @@ Optab	optab[] =
 
 	{ ATST,		C_REG,	C_NONE,	C_NONE,		90, 4, 0 },
 
+	{ ALDREXD,	C_SOREG,C_NONE,	C_REG,		91, 4, 0 },
+	{ ASTREXD,	C_SOREG,C_REG,	C_REG,		92, 4, 0 },
+
 	{ AXXX,		C_NONE,	C_NONE,	C_NONE,		 0, 4, 0 },
 };
diff --git a/src/cmd/5l/span.c b/src/cmd/5l/span.c
index 220140f433b..482d3e90a23 100644
--- a/src/cmd/5l/span.c
+++ b/src/cmd/5l/span.c
@@ -1054,6 +1054,8 @@ buildop(void)
 
 		case ALDREX:
 		case ASTREX:
+		case ALDREXD:
+		case ASTREXD:
 		case ATST:
 			break;
 		}