[PATCH] D69868: Allow "callbr" to return non-void values

[Bill Wendling via Phabricator via llvm-commits]

void created this revision.
void added reviewers: jyknight, nickdesaulniers, hfinkel.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

THIS IS A WIP!

Remove the restrictions that preventing "callbr" from returning non-void
values. The value returned by "callbr" is only valid on the "normal" path.
Values used on "abnormal" paths are poisoned.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D69868

Files:
  llvm/lib/AsmParser/LLParser.cpp
  llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
  llvm/lib/IR/Verifier.cpp
  llvm/test/CodeGen/X86/callbr-asm-outputs.ll


Index: llvm/test/CodeGen/X86/callbr-asm-outputs.ll
===================================================================
--- llvm/test/CodeGen/X86/callbr-asm-outputs.ll
+++ llvm/test/CodeGen/X86/callbr-asm-outputs.ll
@@ -1,18 +1,26 @@
-; RUN: not llc -mtriple=i686-- < %s 2> %t
-; RUN: FileCheck %s < %t
+; RUN: llc -mtriple=i686-- < %s | FileCheck %s
 
-; CHECK: error: asm-goto outputs not supported
+; A test for asm-goto output
 
-; A test for asm-goto output prohibition
-
-define i32 @test(i32 %a) {
+; CHECK-LABEL: test1:
+; CHECK:       movl 4(%esp), %eax
+; CHECK-NEXT:  addl $4, %eax
+; CHECK-NEXT:  #APP
+; CHECK-NEXT:  xorl %eax, %eax
+; CHECK-NEXT:  jmp .Ltmp0
+; CHECK-NEXT:  #NO_APP
+; CHECK-NEXT:  .LBB0_1:
+; CHECK-NEXT:  retl
+; CHECK-NEXT:  .Ltmp0:
+define i32 @test1(i32 %x) {
 entry:
-  %0 = add i32 %a, 4
-  %1 = callbr i32 asm "xorl $1, $1; jmp ${1:l}", "=&r,r,X,~{dirflag},~{fpsr},~{flags}"(i32 %0, i8* blockaddress(@test, %fail)) to label %normal [label %fail]
+  %add = add nsw i32 %x, 4
+  %ret = callbr i32 asm "xorl $1, $0; jmp ${2:l}", "=r,r,X,~{dirflag},~{fpsr},~{flags}"(i32 %add, i8* blockaddress(@test1, %abnormal))
+          to label %normal [label %abnormal]
 
 normal:
-  ret i32 %1
+  ret i32 %ret
 
-fail:
+abnormal:
   ret i32 1
 }
Index: llvm/lib/IR/Verifier.cpp
===================================================================
--- llvm/lib/IR/Verifier.cpp
+++ llvm/lib/IR/Verifier.cpp
@@ -2492,8 +2492,6 @@
 void Verifier::visitCallBrInst(CallBrInst &CBI) {
   Assert(CBI.isInlineAsm(), "Callbr is currently only used for asm-goto!",
          &CBI);
-  Assert(CBI.getType()->isVoidTy(), "Callbr return value is not supported!",
-         &CBI);
   for (unsigned i = 0, e = CBI.getNumSuccessors(); i != e; ++i)
     Assert(CBI.getSuccessor(i)->getType()->isLabelTy(),
            "Callbr successors must all have pointer type!", &CBI);
Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2834,6 +2834,7 @@
   assert(isa<InlineAsm>(I.getCalledValue()) &&
          "Only know how to handle inlineasm callbr");
   visitInlineAsm(&I);
+  CopyToExportRegsIfNeeded(&I);
 
   // Retrieve successors.
   MachineBasicBlock *Return = FuncInfo.MBBMap[I.getDefaultDest()];
Index: llvm/lib/AsmParser/LLParser.cpp
===================================================================
--- llvm/lib/AsmParser/LLParser.cpp
+++ llvm/lib/AsmParser/LLParser.cpp
@@ -6416,9 +6416,6 @@
                           /*IsCall=*/true))
     return true;
 
-  if (isa<InlineAsm>(Callee) && !Ty->getReturnType()->isVoidTy())
-    return Error(RetTypeLoc, "asm-goto outputs not supported");
-
   // Set up the Attribute for the function.
   SmallVector<Value *, 8> Args;
   SmallVector<AttributeSet, 8> ArgAttrs;


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