[Thumb] Handle addressing mode AddrMode5FP16

[SjoerdMeijer]

Summary

This addressing mode wasn't checked, so we were running in an assert.

[olista01]

lib/Target/ARM/Thumb2InstrInfo.cpp

611

Why is this multiplied by 4, and not 2?

test/CodeGen/ARM/fp16-instructions.ll

708

There is a half-precision load in the IR, does this generate a vldr.16? if so, we should be checking that.

715

This test will be fragile WRT changes in stack layout, so we should use a regex for the offset.

[SjoerdMeijer]

Thanks for the review. Feedback addressed.

[olista01]

LGTM, thanks

lib/Target/ARM/Thumb2InstrInfo.cpp

if (AddrMode == ARMII::AddrModeT2_i8 || AddrMode == ARMII::AddrModeT2_i12) {
       NumBits = 8;
       Scale = 4;
       Offset += InstrOffs * 4;
       assert((Offset & (Scale-1)) == 0 && "Can't encode this offset!");
       if (Offset < 0) {
         Offset = -Offset;
         isSub = true;
       }
+    } else if (AddrMode == ARMII::AddrMode5FP16) {
+      // VFP address mode.
+      const MachineOperand &OffOp = MI.getOperand(FrameRegIdx+1);
+      int InstrOffs = ARM_AM::getAM5FP16Offset(OffOp.getImm());
+      if (ARM_AM::getAM5FP16Op(OffOp.getImm()) == ARM_AM::sub)
+        InstrOffs *= -1;
+      NumBits = 8;
+      Scale = 2;
+      Offset += InstrOffs * 4;
+      assert((Offset & (Scale-1)) == 0 && "Can't encode this offset!");
+      if (Offset < 0) {
+        Offset = -Offset;
+        isSub = true;
+      }
     } else if (AddrMode == ARMII::AddrModeT2_i8s4) {
       Offset += MI.getOperand(FrameRegIdx + 1).getImm() * 4;
       NumBits = 10; // 8 bits scaled by 4
       // MCInst operand expects already scaled value.
       Scale = 1;
       assert((Offset & 3) == 0 && "Can't encode this offset!");
     } else {
       llvm_unreachable("Unsupported addressing mode!");

test/CodeGen/ARM/fp16-instructions.ll

 
 ; CHECK-HARDFP-FP16:  vcvtb.f32.f16 [[S2:s[0-9]]], s1
 ; CHECK-HARDFP-FP16:  vcvtb.f32.f16 [[S0:s[0-9]]], s0
 ; CHECK-HARDFP-FP16:  vsub.f32  [[S0]], [[S0]], [[S2]]
 ; CHECK-HARDFP-FP16:  vcvtb.f16.f32 [[S0]], [[S0]]
 
 ; CHECK-HARDFP-FULLFP16:       vsub.f16  s0, s0, s1
 }
+
+; Check for VSTRH with a FCONSTH, this checks that addressing mode
+; AddrMode5FP16 is supported.
+define i32 @ThumbAddrMode5FP16(i32 %A.coerce) {
+entry:
+  %S = alloca half, align 2
+  %tmp.0.extract.trunc = trunc i32 %A.coerce to i16
+  %0 = bitcast i16 %tmp.0.extract.trunc to half
+  %S.0.S.0..sroa_cast = bitcast half* %S to i8*
+  store volatile half 0xH3C00, half* %S, align 2
+  %S.0.S.0. = load volatile half, half* %S, align 2
+  %add = fadd half %S.0.S.0., %0
+  %1 = bitcast half %add to i16
+  %tmp2.0.insert.ext = zext i16 %1 to i32
+  ret i32 %tmp2.0.insert.ext
+
+; CHECK-LABEL:            ThumbAddrMode5FP16
+; CHECK-SOFTFP-FULLFP16:  vstr.16 s0, [sp, #2]
+}