[llvm] r332444 - [AArch64] Support "S" inline assembler constraint

[Peter Smith via llvm-commits]

Author: psmith
Date: Wed May 16 02:33:25 2018
New Revision: 332444

URL: http://llvm.org/viewvc/llvm-project?rev=332444&view=rev
Log:
[AArch64] Support "S" inline assembler constraint

This patch re-introduces the "S" inline assembler constraint. This matches
an absolute symbolic address or a label reference. The primary use case is

asm("adrp %0, %1\n\t"
    "add %0, %0, :lo12:%1" : "=r"(addr) : "S"(&var));

I say re-introduces as it seems like "S" was implemented in the original
AArch64 backend, but it looks like it wasn't carried forward to the merged
backend. The original implementation had A and L modifiers that could be
used to print ":lo12:" to the string. It looks like gcc doesn't use these
and :lo12: is expected to be written in the inline assembly string so I've
not implemented A and L. Clang already supports the S modifier.

Fixes PR37180

Differential Revision: https://reviews.llvm.org/D46745


Added:
    llvm/trunk/test/CodeGen/AArch64/inlineasm-S-constraint.ll
Modified:
    llvm/trunk/lib/Target/AArch64/AArch64AsmPrinter.cpp
    llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp

Modified: llvm/trunk/lib/Target/AArch64/AArch64AsmPrinter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64AsmPrinter.cpp?rev=332444&r1=332443&r2=332444&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64AsmPrinter.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64AsmPrinter.cpp Wed May 16 02:33:25 2018
@@ -276,6 +276,11 @@ void AArch64AsmPrinter::printOperand(con
     printOffset(MO.getOffset(), O);
     break;
   }
+  case MachineOperand::MO_BlockAddress: {
+    MCSymbol *Sym = GetBlockAddressSymbol(MO.getBlockAddress());
+    Sym->print(O, MAI);
+    break;
+  }
   }
 }
 

Modified: llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp?rev=332444&r1=332443&r2=332444&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp Wed May 16 02:33:25 2018
@@ -5212,7 +5212,7 @@ SDValue AArch64TargetLowering::getRecipE
 
 // Table of Constraints
 // TODO: This is the current set of constraints supported by ARM for the
-// compiler, not all of them may make sense, e.g. S may be difficult to support.
+// compiler, not all of them may make sense.
 //
 // r - A general register
 // w - An FP/SIMD register of some size in the range v0-v31
@@ -5272,6 +5272,8 @@ AArch64TargetLowering::getConstraintType
     // currently handle addresses it is the same as 'r'.
     case 'Q':
       return C_Memory;
+    case 'S': // A symbolic address
+      return C_Other;
     }
   }
   return TargetLowering::getConstraintType(Constraint);
@@ -5396,6 +5398,23 @@ void AArch64TargetLowering::LowerAsmOper
       Result = DAG.getRegister(AArch64::WZR, MVT::i32);
     break;
   }
+  case 'S': {
+    // An absolute symbolic address or label reference.
+    if (const GlobalAddressSDNode *GA = dyn_cast<GlobalAddressSDNode>(Op)) {
+      Result = DAG.getTargetGlobalAddress(GA->getGlobal(), SDLoc(Op),
+                                          GA->getValueType(0));
+    } else if (const BlockAddressSDNode *BA =
+                   dyn_cast<BlockAddressSDNode>(Op)) {
+      Result =
+          DAG.getTargetBlockAddress(BA->getBlockAddress(), BA->getValueType(0));
+    } else if (const ExternalSymbolSDNode *ES =
+                   dyn_cast<ExternalSymbolSDNode>(Op)) {
+      Result =
+          DAG.getTargetExternalSymbol(ES->getSymbol(), ES->getValueType(0));
+    } else
+      return;
+    break;
+  }
 
   case 'I':
   case 'J':

Added: llvm/trunk/test/CodeGen/AArch64/inlineasm-S-constraint.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/inlineasm-S-constraint.ll?rev=332444&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/inlineasm-S-constraint.ll (added)
+++ llvm/trunk/test/CodeGen/AArch64/inlineasm-S-constraint.ll Wed May 16 02:33:25 2018
@@ -0,0 +1,20 @@
+;RUN: llc -mtriple=aarch64-none-linux-gnu -mattr=+neon < %s | FileCheck %s
+ at var = global i32 0
+define void @test_inline_constraint_S() {
+; CHECK-LABEL: test_inline_constraint_S:
+  call void asm sideeffect "adrp x0, $0", "S"(i32* @var)
+  call void asm sideeffect "add x0, x0, :lo12:$0", "S"(i32* @var)
+; CHECK: adrp x0, var
+; CHECK: add x0, x0, :lo12:var
+  ret void
+}
+define i32 @test_inline_constraint_S_label(i1 %in) {
+; CHECK-LABEL: test_inline_constraint_S_label:
+  call void asm sideeffect "adr x0, $0", "S"(i8* blockaddress(@test_inline_constraint_S_label, %loc))
+; CHECK: adr x0, .Ltmp{{[0-9]+}}
+br i1 %in, label %loc, label %loc2
+loc:
+  ret i32 0
+loc2:
+  ret i32 42
+}