ARM: Fix incorrect pack pattern for thumb2
Propagate the fix from r185712 to Thumb2 codegen as well. Original
commit message applies here as well:
A "pkhtb x, x, y asr #num" uses the lower 16 bits of "y asr #num" and
packs them in the bottom half of "x". An arithmetic and logic shift are
only equivalent in this context if the shift amount is 16. We would be
shifting in ones into the bottom 16bits instead of zeros if "y" is
negative.
rdar://14338767
llvm-svn: 185982
diff --git a/llvm/test/CodeGen/Thumb2/thumb2-pack.ll b/llvm/test/CodeGen/Thumb2/thumb2-pack.ll
index 2e8bb1d..5deae1b 100644
--- a/llvm/test/CodeGen/Thumb2/thumb2-pack.ll
+++ b/llvm/test/CodeGen/Thumb2/thumb2-pack.ll
@@ -88,10 +88,33 @@
}
; CHECK: test8
-; CHECK: pkhtb r0, r0, r1, asr #22
+; CHECK-NOT: pkhtb r0, r0, r1, asr #22
+; pkhtb does an arithmetic shift, not a logical shift. Make sure we don't
+; use it for problematic cases when whether sign bits would be shifted in
+; would matter.
define i32 @test8(i32 %X, i32 %Y) {
%tmp1 = and i32 %X, -65536
%tmp3 = lshr i32 %Y, 22
%tmp57 = or i32 %tmp3, %tmp1
ret i32 %tmp57
}
+
+; CHECK: test9:
+; CHECK: pkhtb r0, r0, r1, asr #16
+define i32 @test9(i32 %src1, i32 %src2) {
+entry:
+ %tmp = and i32 %src1, -65536
+ %tmp2 = lshr i32 %src2, 16
+ %tmp3 = or i32 %tmp, %tmp2
+ ret i32 %tmp3
+}
+
+; CHECK: test10
+; CHECK: pkhtb r0, r0, r1, asr #22
+define i32 @test10(i32 %X, i32 %Y) {
+ %tmp1 = and i32 %X, -65536
+ %tmp3 = ashr i32 %Y, 22
+ %tmp57 = or i32 %tmp3, %tmp1
+ ret i32 %tmp57
+}
+