Allow output constraints on "asm goto"

Summary:
Remove the restrictions that preventing "asm goto" from returning non-void
values. The values returned by "asm goto" are only valid on the "fallthrough"
path.

Reviewers: jyknight, nickdesaulniers, hfinkel

Reviewed By: jyknight, nickdesaulniers

Subscribers: rsmith, hiraditya, llvm-commits, cfe-commits, craig.topper, rnk

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D69876

1 files changed, 37 insertions, 13 deletions

diff --git a/llvm/lib/CodeGen/MachineVerifier.cpp b/llvm/lib/CodeGen/MachineVerifier.cpp
index ca57e51..cbafd38 100644
--- a/llvm/lib/CodeGen/MachineVerifier.cpp
+++ b/llvm/lib/CodeGen/MachineVerifier.cpp
@@ -633,17 +633,30 @@ MachineVerifier::visitMachineBasicBlockBefore(const MachineBasicBlock *MBB) {
   }
 
   // Count the number of landing pad successors.
-  SmallPtrSet<MachineBasicBlock*, 4> LandingPadSuccs;
-  for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
-       E = MBB->succ_end(); I != E; ++I) {
-    if ((*I)->isEHPad())
-      LandingPadSuccs.insert(*I);
-    if (!FunctionBlocks.count(*I))
+  SmallPtrSet<const MachineBasicBlock*, 4> LandingPadSuccs;
+  for (const auto *succ : MBB->successors()) {
+    if (succ->isEHPad())
+      LandingPadSuccs.insert(succ);
+    if (!FunctionBlocks.count(succ))
       report("MBB has successor that isn't part of the function.", MBB);
-    if (!MBBInfoMap[*I].Preds.count(MBB)) {
+    if (!MBBInfoMap[succ].Preds.count(MBB)) {
       report("Inconsistent CFG", MBB);
       errs() << "MBB is not in the predecessor list of the successor "
-             << printMBBReference(*(*I)) << ".\n";
+             << printMBBReference(*succ) << ".\n";
+    }
+  }
+
+  // Count the number of INLINEASM_BR indirect pad successors.
+  SmallPtrSet<const MachineBasicBlock*, 4> IndirectPadSuccs;
+  for (const auto *succ : MBB->successors()) {
+    if (succ->isInlineAsmBrIndirectPad())
+      IndirectPadSuccs.insert(succ);
+    if (!FunctionBlocks.count(succ))
+      report("MBB has successor that isn't part of the function.", MBB);
+    if (!MBBInfoMap[succ].Preds.count(MBB)) {
+      report("Inconsistent CFG", MBB);
+      errs() << "MBB is not in the predecessor list of the successor "
+             << printMBBReference(*succ) << ".\n";
     }
   }
 
@@ -684,11 +697,13 @@ MachineVerifier::visitMachineBasicBlockBefore(const MachineBasicBlock *MBB) {
         // It's possible that the block legitimately ends with a noreturn
         // call or an unreachable, in which case it won't actually fall
         // out the bottom of the function.
-      } else if (MBB->succ_size() == LandingPadSuccs.size()) {
+      } else if (MBB->succ_size() == LandingPadSuccs.size() ||
+                 MBB->succ_size() == IndirectPadSuccs.size()) {
         // It's possible that the block legitimately ends with a noreturn
         // call or an unreachable, in which case it won't actually fall
         // out of the block.
-      } else if (MBB->succ_size() != 1+LandingPadSuccs.size()) {
+      } else if (MBB->succ_size() != 1 + LandingPadSuccs.size() &&
+                 MBB->succ_size() != 1 + IndirectPadSuccs.size()) {
         report("MBB exits via unconditional fall-through but doesn't have "
                "exactly one CFG successor!", MBB);
       } else if (!MBB->isSuccessor(&*MBBI)) {
@@ -710,7 +725,10 @@ MachineVerifier::visitMachineBasicBlockBefore(const MachineBasicBlock *MBB) {
       // landingpad, accept it as valid control flow.
       if (MBB->succ_size() != 1+LandingPadSuccs.size() &&
           (MBB->succ_size() != 1 || LandingPadSuccs.size() != 1 ||
-           *MBB->succ_begin() != *LandingPadSuccs.begin())) {
+           *MBB->succ_begin() != *LandingPadSuccs.begin()) &&
+          MBB->succ_size() != 1 + IndirectPadSuccs.size() &&
+          (MBB->succ_size() != 1 || IndirectPadSuccs.size() != 1 ||
+           *MBB->succ_begin() != *IndirectPadSuccs.begin())) {
         report("MBB exits via unconditional branch but doesn't have "
                "exactly one CFG successor!", MBB);
       } else if (!MBB->isSuccessor(TBB)) {
@@ -840,8 +858,14 @@ void MachineVerifier::visitMachineBundleBefore(const MachineInstr *MI) {
     if (!FirstTerminator)
       FirstTerminator = MI;
   } else if (FirstTerminator && !MI->isDebugEntryValue()) {
-    report("Non-terminator instruction after the first terminator", MI);
-    errs() << "First terminator was:\t" << *FirstTerminator;
+    // An "INLINEASM_BR" will fallthrough to the successor block executing any
+    // "COPY" instructions that exist so that they can be assigned in the
+    // fallthrough block..
+    if (FirstTerminator->getOpcode() != TargetOpcode::INLINEASM_BR ||
+        MI->getOpcode() != TargetOpcode::COPY) {
+      report("Non-terminator instruction after the first terminator", MI);
+      errs() << "First terminator was:\t" << *FirstTerminator;
+    }
   }
 }