When in ARM mode, LDRH/STRH require special handling of negative offsets.

For correctness, disable this for now.
rdar://10418009

llvm-svn: 144316

llvm/lib/Target/ARM/ARMFastISel.cpp

@@ -852,7 +852,8 @@ void ARMFastISel::ARMSimplifyAddress(Address &Addr, EVT VT) {
         needsLowering = ((Addr.Offset & 0xfff) != Addr.Offset);
       else
         // ARM i16 integer loads/stores handle +/-imm8 offsets.
-        if (Addr.Offset > 255 || Addr.Offset < -255)
+        // FIXME: Negative offsets require special handling.
+        if (Addr.Offset > 255 || Addr.Offset < 0)
           needsLowering = true;
       break;
     case MVT::i1:

llvm/test/CodeGen/ARM/fast-isel-ldrh-strh-arm.ll

@@ -0,0 +1,138 @@
+; RUN: llc < %s -O0 -fast-isel-abort -relocation-model=dynamic-no-pic -mtriple=armv7-apple-darwin | FileCheck %s --check-prefix=ARM
+; rdar://10418009
+
+; TODO: We currently don't support ldrh/strh for negative offsets.  Likely a 
+; rare case, but possibly worth pursuing.  Comments above the test case show
+; what could be selected.
+
+; ldrh r0, [r0, #-16]
+define zeroext i16 @t1(i16* nocapture %a) nounwind uwtable readonly ssp {
+entry:
+; ARM: t1
+  %add.ptr = getelementptr inbounds i16* %a, i64 -8
+  %0 = load i16* %add.ptr, align 2
+; ARM: ldr r{{[1-9]}}, LCPI0_0
+; ARM: add r0, r0, r{{[1-9]}}
+; ARM: ldrh r0, [r0]
+  ret i16 %0
+}
+
+; ldrh r0, [r0, #-32]
+define zeroext i16 @t2(i16* nocapture %a) nounwind uwtable readonly ssp {
+entry:
+; ARM: t2
+  %add.ptr = getelementptr inbounds i16* %a, i64 -16
+  %0 = load i16* %add.ptr, align 2
+; ARM: ldr r{{[1-9]}}, LCPI1_0
+; ARM: add r0, r0, r{{[1-9]}}
+; ARM: ldrh r0, [r0]
+  ret i16 %0
+}
+
+; ldrh r0, [r0, #-254]
+define zeroext i16 @t3(i16* nocapture %a) nounwind uwtable readonly ssp {
+entry:
+; ARM: t3
+  %add.ptr = getelementptr inbounds i16* %a, i64 -127
+  %0 = load i16* %add.ptr, align 2
+; ARM: ldr r{{[1-9]}}, LCPI2_0
+; ARM: add r0, r0, r{{[1-9]}}
+; ARM: ldrh r0, [r0]
+  ret i16 %0
+}
+
+; mvn r1, #255
+; ldrh r0, [r0, r1]
+define zeroext i16 @t4(i16* nocapture %a) nounwind uwtable readonly ssp {
+entry:
+; ARM: t4
+  %add.ptr = getelementptr inbounds i16* %a, i64 -128
+  %0 = load i16* %add.ptr, align 2
+; ARM: ldr r{{[1-9]}}, LCPI3_0
+; ARM: add r0, r0, r{{[1-9]}}
+; ARM: ldrh r0, [r0]
+  ret i16 %0
+}
+
+define zeroext i16 @t5(i16* nocapture %a) nounwind uwtable readonly ssp {
+entry:
+; ARM: t5
+  %add.ptr = getelementptr inbounds i16* %a, i64 8
+  %0 = load i16* %add.ptr, align 2
+; ARM: ldrh r0, [r0, #16]
+  ret i16 %0
+}
+
+define zeroext i16 @t6(i16* nocapture %a) nounwind uwtable readonly ssp {
+entry:
+; ARM: t6
+  %add.ptr = getelementptr inbounds i16* %a, i64 16
+  %0 = load i16* %add.ptr, align 2
+; ARM: ldrh r0, [r0, #32]
+  ret i16 %0
+}
+
+define zeroext i16 @t7(i16* nocapture %a) nounwind uwtable readonly ssp {
+entry:
+; ARM: t7
+  %add.ptr = getelementptr inbounds i16* %a, i64 127
+  %0 = load i16* %add.ptr, align 2
+; ARM: ldrh r0, [r0, #254]
+  ret i16 %0
+}
+
+define zeroext i16 @t8(i16* nocapture %a) nounwind uwtable readonly ssp {
+entry:
+; ARM: t8
+  %add.ptr = getelementptr inbounds i16* %a, i64 128
+  %0 = load i16* %add.ptr, align 2
+; ARM: add r0, r0, #256
+; ARM: ldrh r0, [r0]
+  ret i16 %0
+}
+
+; strh r1, [r0, #-16]
+define void @t9(i16* nocapture %a) nounwind uwtable ssp {
+entry:
+; ARM: t9
+  %add.ptr = getelementptr inbounds i16* %a, i64 -8
+  store i16 0, i16* %add.ptr, align 2
+; ARM: ldr r{{[1-9]}}, LCPI8_0
+; ARM: add r0, r0, r{{[1-9]}}
+; ARM: strh r{{[1-9]}}, [r0]
+  ret void
+}
+
+; mvn r1, #255
+; strh r2, [r0, r1]
+define void @t10(i16* nocapture %a) nounwind uwtable ssp {
+entry:
+; ARM: t10
+  %add.ptr = getelementptr inbounds i16* %a, i64 -128
+  store i16 0, i16* %add.ptr, align 2
+; ARM: ldr r{{[1-9]}}, LCPI9_0
+; ARM: add r0, r0, r{{[1-9]}}
+; ARM: strh r{{[1-9]}}, [r0]
+  ret void
+}
+
+define void @t11(i16* nocapture %a) nounwind uwtable ssp {
+entry:
+; ARM: t11
+  %add.ptr = getelementptr inbounds i16* %a, i64 8
+  store i16 0, i16* %add.ptr, align 2
+; ARM strh r{{[1-9]}}, [r0, #16]
+  ret void
+}
+
+; mov r1, #256
+; strh r2, [r0, r1]
+define void @t12(i16* nocapture %a) nounwind uwtable ssp {
+entry:
+; ARM: t12
+  %add.ptr = getelementptr inbounds i16* %a, i64 128
+  store i16 0, i16* %add.ptr, align 2
+; ARM: add r0, r0, #256
+; ARM: strh r{{[1-9]}}, [r0]
+  ret void
+}