diff --git a/js/src/lirasm/LInsClasses.tbl b/js/src/lirasm/LInsClasses.tbl
index 2a0a80de3de..732e87d5fe6 100644
--- a/js/src/lirasm/LInsClasses.tbl
+++ b/js/src/lirasm/LInsClasses.tbl
@@ -1,5 +1,5 @@
 /* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
- * vim: set ts=8 sw=4 et tw=0 ft=C:
+ * vim: set ts=8 sw=4 et tw=0 ft=c:
  *
  * ***** BEGIN LICENSE BLOCK *****
  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
diff --git a/js/src/lirasm/lirasm.cpp b/js/src/lirasm/lirasm.cpp
index 186c7b19b52..cd405b18fad 100644
--- a/js/src/lirasm/lirasm.cpp
+++ b/js/src/lirasm/lirasm.cpp
@@ -2263,7 +2263,13 @@ processCmdLine(int argc, char **argv, CmdLineOptions& opts)
     avmplus::AvmCore::config.i386_use_cmov = avmplus::AvmCore::config.i386_sse2 = i386_sse;
     avmplus::AvmCore::config.i386_fixed_esp = true;
 #elif defined NANOJIT_ARM
-    // Note that we don't check for sensible configurations here!
+    // Warn about untested configurations.
+    if ( ((arm_arch == 5) && (arm_vfp)) || ((arm_arch >= 6) && (!arm_vfp)) ) {
+        char const * vfp_string = (arm_vfp) ? ("VFP") : ("no VFP");
+        cerr << "Warning: This configuration (ARMv" << arm_arch << ", " << vfp_string << ") " <<
+                "is not regularly tested." << endl;
+    }
+
     avmplus::AvmCore::config.arm_arch = arm_arch;
     avmplus::AvmCore::config.arm_vfp = arm_vfp;
     avmplus::AvmCore::config.soft_float = !arm_vfp;
diff --git a/js/src/lirasm/testlirc.sh b/js/src/lirasm/testlirc.sh
index 25cff6a12c2..e6a608f6cdf 100755
--- a/js/src/lirasm/testlirc.sh
+++ b/js/src/lirasm/testlirc.sh
@@ -6,34 +6,75 @@ LIRASM=$1
 
 TESTS_DIR=`dirname "$0"`/tests
 
-for infile in "$TESTS_DIR"/*.in
-do
-    outfile=`echo $infile | sed 's/\.in/\.out/'`
-    if [ ! -e "$outfile" ]
+function runtest {
+    local infile=$1
+    local options=${2-}
+
+    # Catch a request for the random tests.
+    if [[ $infile == --random* ]]
+    then
+        local outfile=$TESTS_DIR/random.out
+    else
+        local outfile=`echo $infile | sed 's/\.in/\.out/'`
+    fi
+
+    if [[ ! -e "$outfile" ]]
     then
         echo "$0: error: no out file $outfile"
         exit 1
     fi
 
-    # Treat "random.in" and "random-opt.in" specially.
-    if [ `basename $infile` = "random.in" ]
+    if $LIRASM $options --execute $infile | tr -d '\r' > testoutput.txt && cmp -s testoutput.txt $outfile
     then
-        infile="--random 1000000"
-    elif [ `basename $infile` = "random-opt.in" ]
-    then
-        infile="--random 1000000 --optimize"
-    fi
-
-    if $LIRASM --execute $infile | tr -d '\r' > testoutput.txt && cmp -s testoutput.txt $outfile
-    then
-        echo "TEST-PASS | lirasm | lirasm --execute $infile"
+        echo "TEST-PASS | lirasm | lirasm $options --execute $infile"
     else
-        echo "TEST-UNEXPECTED-FAIL | lirasm | lirasm --execute $infile"
+        echo "TEST-UNEXPECTED-FAIL | lirasm | lirasm $options --execute $infile"
         echo "expected output"
         cat $outfile
         echo "actual output"
         cat testoutput.txt
     fi
+}
+
+# Tests common to all supported back-ends.
+for infile in "$TESTS_DIR"/*.in
+do
+    runtest $infile
 done
 
+runtest "--random 1000000"
+runtest "--random 1000000 --optimize"
+
+# ---- Platform-specific tests and configurations. ----
+
+# ARM
+if [[ $(uname -m) == arm* ]]
+then
+    for infile in "$TESTS_DIR"/*.in
+    do
+        # Run standard tests, but set code generation for older architectures.
+        # It may also be beneficial to test ARMv6 and ARMv7 with --novfp, but such
+        # a platform seems so unlikely that it probably isn't worthwhile. It's also
+        # unlikely that it's worth testing ARMv5 with VFP.
+        runtest $infile "--arch 6"
+        runtest $infile "--arch 5 --novfp"
+    done
+
+    # Run specific soft-float tests, but only for ARMv5 without VFP.
+    # NOTE: It looks like MIPS ought to be able to run these tests, but I can't
+    # test this and _not_ running them seems like the safest option.
+    for infile in "$TESTS_DIR"/softfloat/*.in
+    do
+        runtest $infile "--arch 5 --novfp"
+    done
+
+    # Run reduced random tests for these targets. (The default ARMv7 target
+    # still runs the long tests.)
+    runtest "--random 10000 --arch 6"
+    runtest "--random 10000 --arch 5 --novfp"
+    runtest "--random 10000 --optimize --arch 6"
+    runtest "--random 10000 --optimize --arch 5 --novfp"
+fi
+
 rm testoutput.txt
+
diff --git a/js/src/lirasm/tests/random-opt.in b/js/src/lirasm/tests/random-opt.in
deleted file mode 100644
index 425c12166f1..00000000000
--- a/js/src/lirasm/tests/random-opt.in
+++ /dev/null
@@ -1 +0,0 @@
-# dummy file, contents aren't used
diff --git a/js/src/lirasm/tests/random.in b/js/src/lirasm/tests/random.in
deleted file mode 100644
index 425c12166f1..00000000000
--- a/js/src/lirasm/tests/random.in
+++ /dev/null
@@ -1 +0,0 @@
-# dummy file, contents aren't used
diff --git a/js/src/lirasm/tests/softfloat/dhi2i.in b/js/src/lirasm/tests/softfloat/dhi2i.in
new file mode 100644
index 00000000000..89b7d55daec
--- /dev/null
+++ b/js/src/lirasm/tests/softfloat/dhi2i.in
@@ -0,0 +1,4 @@
+; IEEE-754 encodes -0.0 as 0x80000000,00000000
+d = immd -0.0
+hi = dhi2i d
+reti hi
diff --git a/js/src/lirasm/tests/softfloat/dhi2i.out b/js/src/lirasm/tests/softfloat/dhi2i.out
new file mode 100644
index 00000000000..b0b45d5343b
--- /dev/null
+++ b/js/src/lirasm/tests/softfloat/dhi2i.out
@@ -0,0 +1 @@
+Output is: -2147483648
diff --git a/js/src/lirasm/tests/softfloat/dlo2i.in b/js/src/lirasm/tests/softfloat/dlo2i.in
new file mode 100644
index 00000000000..cdf01dc9665
--- /dev/null
+++ b/js/src/lirasm/tests/softfloat/dlo2i.in
@@ -0,0 +1,4 @@
+; IEEE-754 encodes the following constant as 0x3ff00000,ffffffff
+d = immd 1.0000009536743162
+lo = dlo2i d
+reti lo
diff --git a/js/src/lirasm/tests/softfloat/dlo2i.out b/js/src/lirasm/tests/softfloat/dlo2i.out
new file mode 100644
index 00000000000..7bf0fb6c35d
--- /dev/null
+++ b/js/src/lirasm/tests/softfloat/dlo2i.out
@@ -0,0 +1 @@
+Output is: -1
diff --git a/js/src/lirasm/tests/softfloat/ii2d.in b/js/src/lirasm/tests/softfloat/ii2d.in
new file mode 100644
index 00000000000..7189917b863
--- /dev/null
+++ b/js/src/lirasm/tests/softfloat/ii2d.in
@@ -0,0 +1,20 @@
+; It's very difficult to test that the 'lo' part is actually doing anything
+; because it tends to get lost when lirasm dumps the result to the console.
+; By far the easiest way to check this is to use dlo2i and dhi2i to see if we
+; get what we started with (assuming that those instructions work).
+
+hi = immi 1127219201    ; 0x43300001 (positive, exponent of +52 ...
+lo = immi -1            ; 0xffffffff (... mantissa of 0x100001ffffffff)
+d = ii2d lo hi
+hi2 = dhi2i d
+lo2 = dlo2i d
+
+; XOR to check for differences, then OR the two results. 0 indicates success,
+; but anything else indicates some kind of loss of data.
+rhi = xori hi hi2
+rlo = xori lo lo2
+
+res = ori rhi rlo
+
+reti res
+
diff --git a/js/src/lirasm/tests/random-opt.out b/js/src/lirasm/tests/softfloat/ii2d.out
similarity index 100%
rename from js/src/lirasm/tests/random-opt.out
rename to js/src/lirasm/tests/softfloat/ii2d.out