[llvm] [AMDGPU] Add lit() asm operand modifier for SP3 compatibility. (PR #68839)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-amdgpu

Author: Stanislav Mekhanoshin (rampitec)

<details>
<summary>Changes</summary>

A literal can be optionally wrapped in a lit() expression. This does not force literal encoding for an inline immediate, but neither does SP3. The syntax is dummy for compatibility only.

---
Full diff: https://github.com/llvm/llvm-project/pull/68839.diff


2 Files Affected:

- (modified) llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp (+15-3) 
- (modified) llvm/test/MC/AMDGPU/literals.s (+36) 


``````````diff
diff --git a/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp b/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
index 35656bcaea1af7f..1e07e8deb560fcb 100644
--- a/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
+++ b/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
@@ -75,6 +75,7 @@ class AMDGPUOperand : public MCParsedAsmOperand {
     bool Abs = false;
     bool Neg = false;
     bool Sext = false;
+    bool Lit = false;
 
     bool hasFPModifiers() const { return Abs || Neg; }
     bool hasIntModifiers() const { return Sext; }
@@ -3005,7 +3006,7 @@ bool
 AMDGPUAsmParser::isNamedOperandModifier(const AsmToken &Token, const AsmToken &NextToken) const {
   if (Token.is(AsmToken::Identifier) && NextToken.is(AsmToken::LParen)) {
     const auto &str = Token.getString();
-    return str == "abs" || str == "neg" || str == "sext";
+    return str == "abs" || str == "neg" || str == "sext" || str == "lit";
   }
   return false;
 }
@@ -3094,6 +3095,7 @@ AMDGPUAsmParser::parseRegOrImmWithFPInputMods(OperandVector &Operands,
                                               bool AllowImm) {
   bool Neg, SP3Neg;
   bool Abs, SP3Abs;
+  bool Lit;
   SMLoc Loc;
 
   // Disable ambiguous constructs like '--1' etc. Should use neg(-1) instead.
@@ -3113,6 +3115,10 @@ AMDGPUAsmParser::parseRegOrImmWithFPInputMods(OperandVector &Operands,
   if (Abs && !skipToken(AsmToken::LParen, "expected left paren after abs"))
     return ParseStatus::Failure;
 
+  Lit = trySkipId("lit");
+  if (Lit && !skipToken(AsmToken::LParen, "expected left paren after lit"))
+    return ParseStatus::Failure;
+
   Loc = getLoc();
   SP3Abs = trySkipToken(AsmToken::Pipe);
   if (Abs && SP3Abs)
@@ -3125,7 +3131,10 @@ AMDGPUAsmParser::parseRegOrImmWithFPInputMods(OperandVector &Operands,
     Res = parseReg(Operands);
   }
   if (!Res.isSuccess())
-    return (SP3Neg || Neg || SP3Abs || Abs) ? ParseStatus::Failure : Res;
+    return (SP3Neg || Neg || SP3Abs || Abs || Lit) ? ParseStatus::Failure : Res;
+
+  if (Lit && !Operands.back()->isImm())
+    Error(Loc, "expected immediate with lit modifier");
 
   if (SP3Abs && !skipToken(AsmToken::Pipe, "expected vertical bar"))
     return ParseStatus::Failure;
@@ -3133,12 +3142,15 @@ AMDGPUAsmParser::parseRegOrImmWithFPInputMods(OperandVector &Operands,
     return ParseStatus::Failure;
   if (Neg && !skipToken(AsmToken::RParen, "expected closing parentheses"))
     return ParseStatus::Failure;
+  if (Lit && !skipToken(AsmToken::RParen, "expected closing parentheses"))
+    return ParseStatus::Failure;
 
   AMDGPUOperand::Modifiers Mods;
   Mods.Abs = Abs || SP3Abs;
   Mods.Neg = Neg || SP3Neg;
+  Mods.Lit = Lit;
 
-  if (Mods.hasFPModifiers()) {
+  if (Mods.hasFPModifiers() || Lit) {
     AMDGPUOperand &Op = static_cast<AMDGPUOperand &>(*Operands.back());
     if (Op.isExpr())
       return Error(Op.getStartLoc(), "expected an absolute expression");
diff --git a/llvm/test/MC/AMDGPU/literals.s b/llvm/test/MC/AMDGPU/literals.s
index 8e5e8fd1886f416..910e3d82b2fc849 100644
--- a/llvm/test/MC/AMDGPU/literals.s
+++ b/llvm/test/MC/AMDGPU/literals.s
@@ -889,3 +889,39 @@ v_pk_add_f16 v255, private_base, private_limit
 // NOSICIVI: :[[@LINE+2]]:{{[0-9]+}}: error: instruction not supported on this GPU
 // NOGFX9: :[[@LINE+1]]:{{[0-9]+}}: error: invalid operand (violates constant bus restrictions)
 v_pk_add_f16 v255, vccz, execz
+
+//---------------------------------------------------------------------------//
+// check dummy lit() syntax for sp3 compatibility.
+//---------------------------------------------------------------------------//
+
+// SICI: v_sqrt_f32_e32 v2, 0x7b                 ; encoding: [0xff,0x66,0x04,0x7e,0x7b,0x00,0x00,0x00]
+// GFX89: v_sqrt_f32_e32 v2, 0x7b                 ; encoding: [0xff,0x4e,0x04,0x7e,0x7b,0x00,0x00,0x00]
+v_sqrt_f32 v2, lit(123)
+
+// SICI: v_sqrt_f32_e32 v2, 0x7b                 ; encoding: [0xff,0x66,0x04,0x7e,0x7b,0x00,0x00,0x00]
+// GFX89: v_sqrt_f32_e32 v2, 0x7b                 ; encoding: [0xff,0x4e,0x04,0x7e,0x7b,0x00,0x00,0x00]
+v_sqrt_f32 v2, abs(lit(123))
+
+// SICI: v_sqrt_f32_e32 v2, 0x42f60000           ; encoding: [0xff,0x66,0x04,0x7e,0x00,0x00,0xf6,0x42
+// GFX89: v_sqrt_f32_e32 v2, 0x42f60000           ; encoding: [0xff,0x4e,0x04,0x7e,0x00,0x00,0xf6,0x42]
+v_sqrt_f32 v2, lit(123.0)
+
+// SICI: v_sqrt_f64_e32 v[2:3], 0x405ec000       ; encoding: [0xff,0x68,0x04,0x7e,0x00,0xc0,0x5e,0x40]
+// GFX89: v_sqrt_f64_e32 v[2:3], 0x405ec000       ; encoding: [0xff,0x50,0x04,0x7e,0x00,0xc0,0x5e,0x40]
+v_sqrt_f64 v[2:3], lit(123.0)
+
+// SICI: v_sqrt_f64_e32 v[2:3], 0x7b             ; encoding: [0xff,0x68,0x04,0x7e,0x7b,0x00,0x00,0x00]
+// GFX89: v_sqrt_f64_e32 v[2:3], 0x7b             ; encoding: [0xff,0x50,0x04,0x7e,0x7b,0x00,0x00,0x00]
+v_sqrt_f64 v[2:3], lit(123)
+
+// NOSICI: :[[@LINE+2]]:{{[0-9]+}}: error: expected left paren after lit
+// NOGFX89: :[[@LINE+1]]:{{[0-9]+}}: error: expected left paren after lit
+v_sqrt_f32 v2, lit 123.0
+
+// NOSICI: :[[@LINE+2]]:{{[0-9]+}}: error: expected closing parentheses
+// NOGFX89: :[[@LINE+1]]:{{[0-9]+}}: error: expected closing parentheses
+v_sqrt_f32 v2, lit(123.0
+
+// NOSICI: :[[@LINE+2]]:{{[0-9]+}}: error: expected immediate with lit modifier
+// NOGFX89: :[[@LINE+1]]:{{[0-9]+}}: error: expected immediate with lit modifier
+v_sqrt_f32 v2, lit(v1)

``````````

</details>


https://github.com/llvm/llvm-project/pull/68839