GlobalISel: support translating va_arg

Since (say) i128 and [16 x i8] map to the same type in generic MIR, we also
need to attach the required alignment info.

llvm-svn: 295254

5 files changed, 38 insertions, 3 deletions

diff --git a/llvm/include/llvm/CodeGen/GlobalISel/IRTranslator.h b/llvm/include/llvm/CodeGen/GlobalISel/IRTranslator.h
index 352eebd58c5..7ed2082f94d 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/IRTranslator.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/IRTranslator.h
@@ -300,6 +300,8 @@ private:
     return translateBinaryOp(TargetOpcode::G_FREM, U, MIRBuilder);
   }
 
+  bool translateVAArg(const User &U, MachineIRBuilder &MIRBuilder);
+
   // Stubs to keep the compiler happy while we implement the rest of the
   // translation.
   bool translateResume(const User &U, MachineIRBuilder &MIRBuilder) {
@@ -338,9 +340,6 @@ private:
   bool translateUserOp2(const User &U, MachineIRBuilder &MIRBuilder) {
     return false;
   }
-  bool translateVAArg(const User &U, MachineIRBuilder &MIRBuilder) {
-    return false;
-  }
   bool translateExtractElement(const User &U, MachineIRBuilder &MIRBuilder) {
     return false;
   }
diff --git a/llvm/include/llvm/Target/GenericOpcodes.td b/llvm/include/llvm/Target/GenericOpcodes.td
index 4c5d61788f2..880fbc46374 100644
--- a/llvm/include/llvm/Target/GenericOpcodes.td
+++ b/llvm/include/llvm/Target/GenericOpcodes.td
@@ -98,6 +98,14 @@ def G_VASTART : Instruction {
   let mayStore = 1;
 }
 
+def G_VAARG : Instruction {
+  let OutOperandList = (outs type0:$val);
+  let InOperandList = (ins type1:$list, unknown:$align);
+  let hasSideEffects = 0;
+  let mayLoad = 1;
+  let mayStore = 1;
+}
+
 //------------------------------------------------------------------------------
 // Binary ops.
 //------------------------------------------------------------------------------
diff --git a/llvm/include/llvm/Target/TargetOpcodes.def b/llvm/include/llvm/Target/TargetOpcodes.def
index b38e0cfc364..2d1ff50ca10 100644
--- a/llvm/include/llvm/Target/TargetOpcodes.def
+++ b/llvm/include/llvm/Target/TargetOpcodes.def
@@ -283,6 +283,9 @@ HANDLE_TARGET_OPCODE(G_FCONSTANT)
 /// Generic va_start instruction. Stores to its one pointer operand.
 HANDLE_TARGET_OPCODE(G_VASTART)
 
+/// Generic va_start instruction. Stores to its one pointer operand.
+HANDLE_TARGET_OPCODE(G_VAARG)
+
 // Generic sign extend
 HANDLE_TARGET_OPCODE(G_SEXT)
 
diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index c5ac42f4430..e80dac1c952 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -906,6 +906,18 @@ bool IRTranslator::translateAlloca(const User &U,
   return true;
 }
 
+bool IRTranslator::translateVAArg(const User &U, MachineIRBuilder &MIRBuilder) {
+  // FIXME: We may need more info about the type. Because of how LLT works,
+  // we're completely discarding the i64/double distinction here (amongst
+  // others). Fortunately the ABIs I know of where that matters don't use va_arg
+  // anyway but that's not guaranteed.
+  MIRBuilder.buildInstr(TargetOpcode::G_VAARG)
+    .addDef(getOrCreateVReg(U))
+    .addUse(getOrCreateVReg(*U.getOperand(0)))
+    .addImm(DL->getABITypeAlignment(U.getType()));
+  return true;
+}
+
 bool IRTranslator::translatePHI(const User &U, MachineIRBuilder &MIRBuilder) {
   const PHINode &PI = cast<PHINode>(U);
   auto MIB = MIRBuilder.buildInstr(TargetOpcode::PHI);
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll b/llvm/test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll
index 418c71e3992..3c06d5c80f7 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll
@@ -1134,6 +1134,19 @@ define void @test_va_end(i8* %list) {
   ret void
 }
 
+define void @test_va_arg(i8* %list) {
+; CHECK-LABEL: test_va_arg
+; CHECK: [[LIST:%[0-9]+]](p0) = COPY %x0
+; CHECK: G_VAARG [[LIST]](p0), 8
+; CHECK: G_VAARG [[LIST]](p0), 1
+; CHECK: G_VAARG [[LIST]](p0), 16
+
+  %v0 = va_arg i8* %list, i64
+  %v1 = va_arg i8* %list, i8
+  %v2 = va_arg i8* %list, i128
+  ret void
+}
+
 declare float @llvm.pow.f32(float, float)
 define float @test_pow_intrin(float %l, float %r) {
 ; CHECK-LABEL: name: test_pow_intrin