[AVR] Add support for the full set of inline asm constraints

[dylanmckay]

Summary

Previously the method would simply return false, causing every single
inline assembly constraint to trigger a compile error.

This adds inline assembly constraint support for the AVR target.

This patch is derived from the code in
AVRISelLowering::getConstraintType.

More details can be found on the AVR-GCC reference wiki
http://www.nongnu.org/avr-libc/user-manual/inline_asm.html

[ahatanak]

Test case?

lib/Basic/Targets.cpp

8506

Is this meant to fall through or do you need a "break" here?

[dylanmckay]

Fix a few cases of unintentional switch fallthrough

[dylanmckay]

Add tests for inline assembly constraints

[dylanmckay]

lib/Basic/Targets.cpp

8506

Nice catch, fixed

[dylanmckay]

Ping

[dylanmckay]

Ping

[asl]

test/CodeGen/avr-inline-asm-constraints.c

2 ↗

(On Diff #83507)

You need checks for multi-character stuff and unsupported constraints.

[dylanmckay]

Add tests

• Add multichar constraint tests
• Add 'unsupported constraint' tests

[dylanmckay]

Add tests

• Add multichar constraint tests
• Add 'unsupported constraint' tests

[asl]

lib/Basic/Targets.cpp

8518

don't you want to have "return false" here, just to silence warning for some compilers?

lib/Basic/Targets.cpp

static const TargetInfo::AddlRegName AddlRegNames[] = {
       { { "r30", "r31"}, 28 },
       { { "SPL", "SPH"}, 29 },
     };
     return llvm::makeArrayRef(AddlRegNames);
   }
 
   bool validateAsmConstraint(const char *&Name,
                              TargetInfo::ConstraintInfo &Info) const override {
-    return false;
+    // There aren't any multi-character AVR specific constraints.
+    if (StringRef(Name).size() > 1) return false;
+
+    switch (*Name) {
+      default: return false;
+      case 'a': // Simple upper registers
+      case 'b': // Base pointer registers pairs
+      case 'd': // Upper register
+      case 'l': // Lower registers
+      case 'e': // Pointer register pairs
+      case 'q': // Stack pointer register
+      case 'r': // Any register
+      case 'w': // Special upper register pairs
+      case 't': // Temporary register
+      case 'x': case 'X': // Pointer register pair X
+      case 'y': case 'Y': // Pointer register pair Y
+      case 'z': case 'Z': // Pointer register pair Z
+        Info.setAllowsRegister();
+        return true;
+      case 'I': // 6-bit positive integer constant
+        Info.setRequiresImmediate(0, 63);
+        return true;
+      case 'J': // 6-bit negative integer constant
+        Info.setRequiresImmediate(-63, 0);
+        return true;
+      case 'K': // Integer constant (Range: 2)
+        Info.setRequiresImmediate(2);
+        return true;
+      case 'L': // Integer constant (Range: 0)
+        Info.setRequiresImmediate(0);
+        return true;
+      case 'M': // 8-bit integer constant
+        Info.setRequiresImmediate(0, 0xff);
+        return true;
+      case 'N': // Integer constant (Range: -1)
+        Info.setRequiresImmediate(-1);
+      case 'O': // Integer constant (Range: 8, 16, 24)
+        Info.setRequiresImmediate({8, 16, 24});
+      case 'P': // Integer constant (Range: 1)
+        Info.setRequiresImmediate(1);
+      case 'R': // Integer constant (Range: -6 to 5)
+        Info.setRequiresImmediate(-6, 5);
+        return true;
+      case 'G': // Floating point constant
+      case 'Q': // A memory address based on Y or Z pointer with displacement.
+        return true;
+    }
   }
 
   IntType getIntTypeByWidth(unsigned BitWidth,
                             bool IsSigned) const final {
     // AVR prefers int for 16-bit integers.
     return BitWidth == 16 ? (IsSigned ? SignedInt : UnsignedInt)
                           : TargetInfo::getIntTypeByWidth(BitWidth, IsSigned);
   }