[PATCH] [PATCH][AArch64] Fix the bug about disassembling incorrect lanes for post-indx of load/store single element instructions.

[Hao Liu]

Hi t.p.northover,

Hi Tim and reviewers,

This patch fixes a critical bug about disassembling about load/store single element instructions. Because of my carelessness, the lanes of such instructions are dissassembled incorrectly.

This patch fixes that bug.

Review please.

As this patch is important to the AArch64's MC layer, could it be merged to branch3.4?

Thanks,
-Hao

http://llvm-reviews.chandlerc.com/D2249

Files:
  lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp
  test/MC/Disassembler/AArch64/neon-instructions.txt

Index: lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp
===================================================================
--- lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp
+++ lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp
@@ -1117,7 +1117,9 @@
   bool Is64bitVec = false;
   bool IsLoadDup = false;
   bool IsLoad = false;
-  unsigned TransferBytes = 0; // The total number of bytes transferred.
+  // The total number of bytes transferred.
+  // TransferBytes = NumVecs * OneLaneBytes
+  unsigned TransferBytes = 0;
   unsigned NumVecs = 0;
   unsigned Opc = Inst.getOpcode();
   switch (Opc) {
@@ -1511,17 +1513,20 @@
   unsigned Q = fieldFromInstruction(Insn, 30, 1);
   unsigned S = fieldFromInstruction(Insn, 10, 3);
   unsigned lane = 0;
-  switch (NumVecs) {
-  case 1:
-    lane = (Q << 3) & S;
+  // Calculate the number of lanes by number of vectors and transfered bytes.
+  // NumLanes = 16 bytes / bytes of each lane
+  unsigned NumLanes = 16 / (TransferBytes / NumVecs);
+  switch (NumLanes) {
+  case 16: // A vector has 16 lanes, each lane is 1 bytes.
+    lane = (Q << 3) | S;
     break;
-  case 2:
-    lane = (Q << 2) & (S >> 1);
-    break;
-  case 3:
-    lane = (Q << 1) & (S >> 2);
+  case 8:
+    lane = (Q << 2) | (S >> 1);
     break;
   case 4:
+    lane = (Q << 1) | (S >> 2);
+    break;
+  case 2:
     lane = Q;
     break;
   }
Index: test/MC/Disassembler/AArch64/neon-instructions.txt
===================================================================
--- test/MC/Disassembler/AArch64/neon-instructions.txt
+++ test/MC/Disassembler/AArch64/neon-instructions.txt
@@ -2126,14 +2126,14 @@
 # Post-index of vector load/store single N-element structure to/from
 #  one lane of N consecutive registers (N = 1,2,3,4)
 #----------------------------------------------------------------------
-# CHECK: ld1 {v0.b}[0], [x0], #1
-# CHECK: ld2 {v15.h, v16.h}[0], [x15], #4
-# CHECK: ld3 {v31.s, v0.s, v1.s}[0], [sp], x3
+# CHECK: ld1 {v0.b}[9], [x0], #1
+# CHECK: ld2 {v15.h, v16.h}[7], [x15], #4
+# CHECK: ld3 {v31.s, v0.s, v1.s}[3], [sp], x3
 # CHECK: ld4 {v0.d, v1.d, v2.d, v3.d}[1], [x0], #24
-# CHECK: st1 {v0.d}[0], [x0], #8
-# CHECK: st2 {v31.s, v0.s}[0], [sp], #8
-# CHECK: st3 {v15.h, v16.h, v17.h}[0], [x15], #6
-# CHECK: st4 {v0.b, v1.b, v2.b, v3.b}[1], [x0], x5
+# CHECK: st1 {v0.d}[1], [x0], #8
+# CHECK: st2 {v31.s, v0.s}[3], [sp], #8
+# CHECK: st3 {v15.h, v16.h, v17.h}[7], [x15], #6
+# CHECK: st4 {v0.b, v1.b, v2.b, v3.b}[9], [x0], x5
 0x00,0x04,0xdf,0x4d
 0xef,0x59,0xff,0x4d
 0xff,0xb3,0xc3,0x4d
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