[llvm] 9fa6a2d - Validate EXT byte-index immediates (#214233)

[via llvm-commits]

Author: Hamza Khan
Date: 2026-08-20T10:13:00+01:00
New Revision: 9fa6a2d79fecd6c9f42db2effca0936254dbf4e4

URL: https://github.com/llvm/llvm-project/commit/9fa6a2d79fecd6c9f42db2effca0936254dbf4e4
DIFF: https://github.com/llvm/llvm-project/commit/9fa6a2d79fecd6c9f42db2effca0936254dbf4e4.diff

LOG: Validate EXT byte-index immediates (#214233)

This fixes operand validation for AArch64 EXT instructions.

Symbolic operands such as f0, NaN, and Inf, as well as out-of-range
byte-index immediates, could previously reach encoding paths that expect
valid integer immediates. This could cause assertion failures in
assertions-enabled builds or incorrect encodings when assertions were
disabled.

The patch uses the appropriate immediate operand ranges for the .8b and
.16b forms so invalid operands are rejected during parsing.

Regression tests cover symbolic operands, out-of-range immediates, and
the valid boundary values #7 and #15.

Testing:

* llvm/test/MC/AArch64/neon-diagnostics.s
* llvm/test/MC/AArch64/neon-extract.s

Fixes #185361

The SCVTF/UCVTF portion originally included in this PR is now covered by
#213490 and was removed after rebasing onto current main.

Added: 
    

Modified: 
    llvm/lib/Target/AArch64/AArch64InstrFormats.td
    llvm/test/MC/AArch64/neon-diagnostics.s
    llvm/test/MC/AArch64/neon-extract.s

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/AArch64/AArch64InstrFormats.td b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
index a4d5c0d97c8ce..68c80f5d112ae 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrFormats.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
@@ -7686,8 +7686,8 @@ multiclass SIMDWideThreeVectorBHS<bit U, bits<4> opc, string asm,
 //----------------------------------------------------------------------------
 
 class BaseSIMDBitwiseExtract<bit size, RegisterOperand regtype, ValueType vty,
-                             string asm, string kind>
-  : I<(outs regtype:$Rd), (ins regtype:$Rn, regtype:$Rm, i32imm:$imm), asm,
+                             Operand immtype, string asm, string kind>
+  : I<(outs regtype:$Rd), (ins regtype:$Rn, regtype:$Rm, immtype:$imm), asm,
       "{\t$Rd" # kind # ", $Rn" # kind # ", $Rm" # kind # ", $imm" #
       "|" # kind # "\t$Rd, $Rn, $Rm, $imm}", "",
       [(set (vty regtype:$Rd),
@@ -7710,10 +7710,10 @@ class BaseSIMDBitwiseExtract<bit size, RegisterOperand regtype, ValueType vty,
 
 
 multiclass SIMDBitwiseExtract<string asm> {
-  def v8i8  : BaseSIMDBitwiseExtract<0, V64, v8i8, asm, ".8b"> {
+  def v8i8  : BaseSIMDBitwiseExtract<0, V64, v8i8, imm32_0_7, asm, ".8b"> {
     let imm{3} = 0;
   }
-  def v16i8 : BaseSIMDBitwiseExtract<1, V128, v16i8, asm, ".16b">;
+  def v16i8 : BaseSIMDBitwiseExtract<1, V128, v16i8, imm32_0_15, asm, ".16b">;
 }
 
 //----------------------------------------------------------------------------

diff  --git a/llvm/test/MC/AArch64/neon-diagnostics.s b/llvm/test/MC/AArch64/neon-diagnostics.s
index 2610f4acf383b..cfcbf7e336a86 100644
--- a/llvm/test/MC/AArch64/neon-diagnostics.s
+++ b/llvm/test/MC/AArch64/neon-diagnostics.s
@@ -6418,6 +6418,21 @@
 // CHECK-ERROR:         ext v0.2d, v1.2d, v2.2d, #0x0
 // CHECK-ERROR:                ^
 
+        // Symbolic operands are not valid byte-index immediates.
+        ext v0.8b, v1.8b, v2.8b, f0
+// CHECK-ERROR: [[@LINE-1]]:34: error: immediate must be an integer in range [0, 7].
+        ext v0.16b, v1.16b, v2.16b, f0
+// CHECK-ERROR: [[@LINE-1]]:37: error: immediate must be an integer in range [0, 15].
+        ext v0.8b, v1.8b, v2.8b, NaN
+// CHECK-ERROR: [[@LINE-1]]:34: error: immediate must be an integer in range [0, 7].
+        ext v0.8b, v1.8b, v2.8b, Inf
+// CHECK-ERROR: [[@LINE-1]]:34: error: immediate must be an integer in range [0, 7].
+
+        // Out-of-range byte-index immediates must be rejected.
+        ext v0.8b, v1.8b, v2.8b, #8
+// CHECK-ERROR: [[@LINE-1]]:34: error: immediate must be an integer in range [0, 7].
+        ext v0.16b, v1.16b, v2.16b, #16
+// CHECK-ERROR: [[@LINE-1]]:37: error: immediate must be an integer in range [0, 15].
 
 //----------------------------------------------------------------------
 // Permutation with 3 vectors

diff  --git a/llvm/test/MC/AArch64/neon-extract.s b/llvm/test/MC/AArch64/neon-extract.s
index 1daa46d096eee..f37bc0ec3e67d 100644
--- a/llvm/test/MC/AArch64/neon-extract.s
+++ b/llvm/test/MC/AArch64/neon-extract.s
@@ -8,6 +8,10 @@
 
         ext v0.8b, v1.8b, v2.8b, #0x3
         ext v0.16b, v1.16b, v2.16b, #0x3
+        ext v0.8b, v1.8b, v2.8b, #7
+        ext v0.16b, v1.16b, v2.16b, #15
 
 // CHECK: ext	v0.8b, v1.8b, v2.8b, #{{0x3|3}}  // encoding: [0x20,0x18,0x02,0x2e]
 // CHECK: ext	v0.16b, v1.16b, v2.16b, #{{0x3|3}} // encoding: [0x20,0x18,0x02,0x6e]
+// CHECK: ext	v0.8b, v1.8b, v2.8b, #7  // encoding: [0x20,0x38,0x02,0x2e]
+// CHECK: ext	v0.16b, v1.16b, v2.16b, #15 // encoding: [0x20,0x78,0x02,0x6e]
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