[llvm] acd7fe8 - [AArch64][v8.3a] Don't emit LDRA '[xN]!' alias in disassembly.

[Simon Tatham via llvm-commits]

Author: Simon Tatham
Date: 2019-11-28T15:31:59Z
New Revision: acd7fe8636ab1d892a935ca747ed9bb6420e2253

URL: https://github.com/llvm/llvm-project/commit/acd7fe8636ab1d892a935ca747ed9bb6420e2253
DIFF: https://github.com/llvm/llvm-project/commit/acd7fe8636ab1d892a935ca747ed9bb6420e2253.diff

LOG: [AArch64][v8.3a] Don't emit LDRA '[xN]!' alias in disassembly.

Summary:
In rG643ac6c0420b, the syntax `ldraa x1, [x0]!` was added as an alias
for `ldraa x1, [x0, #0]!`. That syntax is less obvious in meaning, and
also will not be accepted by assemblers that haven't been updated yet.
So it would be better not to emit it as the preferred disassembly for
that instruction.

This change lowers the EmitPriority of the new alias so that the more
explicit syntax `[x0, #0]!` is preferred by the disassembler. The new
syntax is still accepted by the assembler.

Reviewers: ab, ostannard

Reviewed By: ostannard

Subscribers: kristof.beyls, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70813

Added: 
    

Modified: 
    llvm/lib/Target/AArch64/AArch64InstrFormats.td
    llvm/test/MC/AArch64/armv8.3a-signed-pointer.s
    llvm/test/MC/Disassembler/AArch64/armv8.3a-signed-pointer.txt

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/AArch64/AArch64InstrFormats.td b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
index 5da790c84617..878cb79eb326 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrFormats.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
@@ -1473,7 +1473,7 @@ multiclass AuthLoad<bit M, string asm, Operand opr> {
                   (!cast<Instruction>(NAME # "indexed") GPR64:$Rt, GPR64sp:$Rn, 0)>;
 
   def : InstAlias<asm # "\t$Rt, [$wback]!",
-                  (!cast<Instruction>(NAME # "writeback") GPR64sp:$wback, GPR64:$Rt, 0)>;
+                  (!cast<Instruction>(NAME # "writeback") GPR64sp:$wback, GPR64:$Rt, 0), 0>;
 }
 
 //---

diff  --git a/llvm/test/MC/AArch64/armv8.3a-signed-pointer.s b/llvm/test/MC/AArch64/armv8.3a-signed-pointer.s
index 2ca15fceccc8..056a3ae86c07 100644
--- a/llvm/test/MC/AArch64/armv8.3a-signed-pointer.s
+++ b/llvm/test/MC/AArch64/armv8.3a-signed-pointer.s
@@ -307,10 +307,10 @@
 // CHECK-REQ: error: instruction requires: pa
 // CHECK-REQ-NEXT:  ldrab x0, [x1]
   ldraa x0, [x1]!
-// CHECK-NEXT: ldraa x0, [x1]!  // encoding: [0x20,0x0c,0x20,0xf8]
+// CHECK-NEXT: ldraa x0, [x1, #0]!  // encoding: [0x20,0x0c,0x20,0xf8]
 // CHECK-REQ: error: instruction requires: pa
 // CHECK-REQ-NEXT:  ldraa x0, [x1]!
   ldrab x0, [x1]!
-// CHECK-NEXT: ldrab x0, [x1]!  // encoding: [0x20,0x0c,0xa0,0xf8]
+// CHECK-NEXT: ldrab x0, [x1, #0]!  // encoding: [0x20,0x0c,0xa0,0xf8]
 // CHECK-REQ: error: instruction requires: pa
 // CHECK-REQ-NEXT:  ldrab x0, [x1]!

diff  --git a/llvm/test/MC/Disassembler/AArch64/armv8.3a-signed-pointer.txt b/llvm/test/MC/Disassembler/AArch64/armv8.3a-signed-pointer.txt
index d11056044fa4..7215d086c693 100644
--- a/llvm/test/MC/Disassembler/AArch64/armv8.3a-signed-pointer.txt
+++ b/llvm/test/MC/Disassembler/AArch64/armv8.3a-signed-pointer.txt
@@ -114,7 +114,7 @@
 [0x20,0x04,0x20,0xf8]
 [0x20,0x04,0xa0,0xf8]
 
-# CHECK: ldraa x0, [x1]!
-# CHECK: ldrab x0, [x1]!
+# CHECK: ldraa x0, [x1, #0]!
+# CHECK: ldrab x0, [x1, #0]!
 [0x20,0x0c,0x20,0xf8]
 [0x20,0x0c,0xa0,0xf8]