[PATCH] D75885: [AArch64] Allow logical immediates to have all-1 in top bits

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: SjoerdMeijer, samparker, sdesmalen.
Herald added subscribers: llvm-commits, danielkiss, hiraditya, kristof.beyls.
Herald added a project: LLVM.
MaskRay updated this revision to Diff 249259.
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So that constant expressions like the following are permitted:

and w0, w0, #~(0xfe<<24)
and w1, w1, #~(0xff<<24)

The behavior matches GNU as (opcodes/aarch64-opc.c:aarch64_logical_immediate_p).

`mov z0.h, #-33024` can now be assembled by MC (also GNu as), but the code sequence disassembles to `dupm z0.h, #-x7f00`.
I left a FIXME in the test.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D75885

Files:
  llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
  llvm/test/MC/AArch64/SVE/mov-diagnostics.s
  llvm/test/MC/AArch64/SVE/mov.s
  llvm/test/MC/AArch64/arm64-logical-encoding.s


Index: llvm/test/MC/AArch64/arm64-logical-encoding.s
===================================================================
--- llvm/test/MC/AArch64/arm64-logical-encoding.s
+++ llvm/test/MC/AArch64/arm64-logical-encoding.s
@@ -222,3 +222,10 @@
 ; CHECK: orn x1, x2, x3, asr #7      ; encoding: [0x41,0x1c,0xa3,0xaa]
 ; CHECK: orn w1, w2, w3, ror #7      ; encoding: [0x41,0x1c,0xe3,0x2a]
 ; CHECK: orn x1, x2, x3, ror #7      ; encoding: [0x41,0x1c,0xe3,0xaa]
+
+;; Allow all-1 in top bits.
+  and w0, w0, #~(0xfe<<24)
+  and w1, w1, #~(0xff<<24)
+
+; CHECK: and w0, w0, #0x1ffffff
+; CHECK: and w1, w1, #0xffffff
Index: llvm/test/MC/AArch64/SVE/mov.s
===================================================================
--- llvm/test/MC/AArch64/SVE/mov.s
+++ llvm/test/MC/AArch64/SVE/mov.s
@@ -205,6 +205,13 @@
 // CHECK-ERROR: instruction requires: sve
 // CHECK-UNKNOWN: e0 ff 78 25 <unknown>
 
+mov     z0.h, #-33024
+/// FIXME
+// CHECK-INST: dupm z0.h, #0x7f00
+// CHECK-ENCODING: [0xc0,0x44,0xc0,0x05]
+// CHECK-ERROR: instruction requires: sve
+// CHECK-UNKNOWN: c0 44 c0 05 <unknown>
+
 mov     z0.s, #-32769
 // CHECK-INST: mov     z0.s, #0xffff7fff
 // CHECK-ENCODING: [0xc0,0x83,0xc0,0x05]
Index: llvm/test/MC/AArch64/SVE/mov-diagnostics.s
===================================================================
--- llvm/test/MC/AArch64/SVE/mov-diagnostics.s
+++ llvm/test/MC/AArch64/SVE/mov-diagnostics.s
@@ -153,16 +153,6 @@
 // CHECK-NEXT: mov z0.b, #1, lsl #8
 // CHECK-NOT: [[@LINE-1]]:{{[0-9]+}}:
 
-mov z0.h, #-33024
-// CHECK: [[@LINE-1]]:{{[0-9]+}}: error: immediate must be an integer in range [-128, 127] or a multiple of 256 in range [-32768, 65280]
-// CHECK-NEXT: mov z0.h, #-33024
-// CHECK-NOT: [[@LINE-1]]:{{[0-9]+}}:
-
-mov z0.h, #-32769
-// CHECK: [[@LINE-1]]:{{[0-9]+}}: error: immediate must be an integer in range [-128, 127] or a multiple of 256 in range [-32768, 65280]
-// CHECK-NEXT: mov z0.h, #-32769
-// CHECK-NOT: [[@LINE-1]]:{{[0-9]+}}:
-
 mov z0.h, #-129, lsl #8
 // CHECK: [[@LINE-1]]:{{[0-9]+}}: error: immediate must be an integer in range [-128, 127] or a multiple of 256 in range [-32768, 65280]
 // CHECK-NEXT: mov z0.h, #-129, lsl #8
Index: llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
===================================================================
--- llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
+++ llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
@@ -757,12 +757,13 @@
       return false;
 
     int64_t Val = MCE->getValue();
-    int64_t SVal = std::make_signed_t<T>(Val);
-    int64_t UVal = std::make_unsigned_t<T>(Val);
-    if (Val != SVal && Val != UVal)
+    // Avoid left shift by 64 directly.
+    uint64_t Upper = UINT64_C(-1) << (sizeof(T) * 4) << (sizeof(T) * 4);
+    // Allow all-0 or all-1 in top bits to permit bitwise NOT.
+    if ((Val & Upper) && (Val & Upper) != Upper)
       return false;
 
-    return AArch64_AM::isLogicalImmediate(UVal, sizeof(T) * 8);
+    return AArch64_AM::isLogicalImmediate(Val & ~Upper, sizeof(T) * 8);
   }
 
   bool isShiftedImm() const { return Kind == k_ShiftedImm; }


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