[llvm] Revert "[AMDGPU][UnifyDivergentExitNodes][StructurizeCFG] Add support for callbr instruction with inline-asm" (PR #166186)

via llvm-commits llvm-commits at lists.llvm.org
Mon Nov 3 07:54:57 PST 2025


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Robert Imschweiler (ro-i)

<details>
<summary>Changes</summary>

Reverts llvm/llvm-project#<!-- -->152161

Need to revert to fix changed logic for the expensive checks. Example failure from the buildbot:

```
******************** TEST 'LLVM :: CodeGen/AMDGPU/callbr.ll' FAILED ********************
Exit Code: 2

Command Output (stdout):
--
# RUN: at line 2
/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/llc -mtriple=amdgcn -mcpu=gfx90a < /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/llvm-project/llvm/test/CodeGen/AMDGPU/callbr.ll | /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/FileCheck /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/llvm-project/llvm/test/CodeGen/AMDGPU/callbr.ll
# executed command: /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/llc -mtriple=amdgcn -mcpu=gfx90a
# .---command stderr------------
# | Pass modifies its input and doesn't report it: Fixup each natural loop to have a single exit block
# | Pass modifies its input and doesn't report it
# | UNREACHABLE executed at /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1404!
# | PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace and instructions to reproduce the bug.
# | Stack dump:
# | 0.  Program arguments: /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/llc -mtriple=amdgcn -mcpu=gfx90a
# | 1.  Running pass 'CallGraph Pass Manager' on module '<stdin>'.
# | 2.  Running pass 'Fixup each natural loop to have a single exit block' on function '@<!-- -->callbr_self_loop'
# |  #<!-- -->0 0x0000585654898ac8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/llc+0x7f68ac8)
# |  #<!-- -->1 0x00005856548961d5 llvm::sys::RunSignalHandlers() (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/llc+0x7f661d5)
# |  #<!-- -->2 0x0000585654899891 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
# |  #<!-- -->3 0x000071c00aa45330 (/lib/x86_64-linux-gnu/libc.so.6+0x45330)
# |  #<!-- -->4 0x000071c00aa9eb2c pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x9eb2c)
# |  #<!-- -->5 0x000071c00aa4527e raise (/lib/x86_64-linux-gnu/libc.so.6+0x4527e)
# |  #<!-- -->6 0x000071c00aa288ff abort (/lib/x86_64-linux-gnu/libc.so.6+0x288ff)
# |  #<!-- -->7 0x00005856547f73af (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/llc+0x7ec73af)
# |  #<!-- -->8 0x0000585653dfd7d2 (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/llc+0x74cd7d2)
# |  #<!-- -->9 0x0000585653328f63 (anonymous namespace)::CGPassManager::runOnModule(llvm::Module&) CallGraphSCCPass.cpp:0:0
# | #<!-- -->10 0x0000585653dfe00a llvm::legacy::PassManagerImpl::run(llvm::Module&) (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/llc+0x74ce00a)
# | #<!-- -->11 0x00005856517664bc compileModule(char**, llvm::LLVMContext&) llc.cpp:0:0
# | #<!-- -->12 0x0000585651763a9d main (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/llc+0x4e33a9d)
# | #<!-- -->13 0x000071c00aa2a1ca (/lib/x86_64-linux-gnu/libc.so.6+0x2a1ca)
# | #<!-- -->14 0x000071c00aa2a28b __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2a28b)
# | #<!-- -->15 0x000058565175f525 _start (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/llc+0x4e2f525)
# `-----------------------------
# error: command failed with exit status: -6
# executed command: /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/FileCheck /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/llvm-project/llvm/test/CodeGen/AMDGPU/callbr.ll
# .---command stderr------------
# | FileCheck error: '<stdin>' is empty.
# | FileCheck command line:  /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/FileCheck /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/llvm-project/llvm/test/CodeGen/AMDGPU/callbr.ll
# `-----------------------------
# error: command failed with exit status: 2
```

---

Patch is 47.03 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/166186.diff


9 Files Affected:

- (modified) llvm/lib/Target/AMDGPU/AMDGPUUnifyDivergentExitNodes.cpp (+35-54) 
- (modified) llvm/lib/Transforms/Scalar/StructurizeCFG.cpp (+8-11) 
- (removed) llvm/test/CodeGen/AMDGPU/callbr.ll (-54) 
- (modified) llvm/test/CodeGen/AMDGPU/do-not-unify-divergent-exit-nodes-with-musttail.ll (-51) 
- (modified) llvm/test/CodeGen/AMDGPU/infinite-loop.ll (+21-236) 
- (modified) llvm/test/CodeGen/AMDGPU/si-annotate-nested-control-flows.ll (+9-91) 
- (modified) llvm/test/CodeGen/AMDGPU/si-unify-exit-multiple-unreachables.ll (+6-155) 
- (modified) llvm/test/CodeGen/AMDGPU/update-phi.ll (-39) 
- (removed) llvm/test/Transforms/StructurizeCFG/callbr.ll (-235) 


``````````diff
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUUnifyDivergentExitNodes.cpp b/llvm/lib/Target/AMDGPU/AMDGPUUnifyDivergentExitNodes.cpp
index 706237b906cc3..733c5d520fb23 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUUnifyDivergentExitNodes.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUUnifyDivergentExitNodes.cpp
@@ -181,52 +181,14 @@ BasicBlock *AMDGPUUnifyDivergentExitNodesImpl::unifyReturnBlockSet(
   return NewRetBlock;
 }
 
-static BasicBlock *
-createDummyReturnBlock(Function &F,
-                       SmallVector<BasicBlock *, 4> &ReturningBlocks) {
-  BasicBlock *DummyReturnBB =
-      BasicBlock::Create(F.getContext(), "DummyReturnBlock", &F);
-  Type *RetTy = F.getReturnType();
-  Value *RetVal = RetTy->isVoidTy() ? nullptr : PoisonValue::get(RetTy);
-  ReturnInst::Create(F.getContext(), RetVal, DummyReturnBB);
-  ReturningBlocks.push_back(DummyReturnBB);
-  return DummyReturnBB;
-}
-
-/// Handle conditional branch instructions (-> 2 targets) and callbr
-/// instructions with N targets.
-static void handleNBranch(Function &F, BasicBlock *BB, Instruction *BI,
-                          BasicBlock *DummyReturnBB,
-                          std::vector<DominatorTree::UpdateType> &Updates) {
-  SmallVector<BasicBlock *, 2> Successors(successors(BB));
-
-  // Create a new transition block to hold the conditional branch.
-  BasicBlock *TransitionBB = BB->splitBasicBlock(BI, "TransitionBlock");
-
-  Updates.reserve(Updates.size() + 2 * Successors.size() + 2);
-
-  // 'Successors' become successors of TransitionBB instead of BB,
-  // and TransitionBB becomes a single successor of BB.
-  Updates.emplace_back(DominatorTree::Insert, BB, TransitionBB);
-  for (BasicBlock *Successor : Successors) {
-    Updates.emplace_back(DominatorTree::Insert, TransitionBB, Successor);
-    Updates.emplace_back(DominatorTree::Delete, BB, Successor);
-  }
-
-  // Create a branch that will always branch to the transition block and
-  // references DummyReturnBB.
-  BB->getTerminator()->eraseFromParent();
-  BranchInst::Create(TransitionBB, DummyReturnBB,
-                     ConstantInt::getTrue(F.getContext()), BB);
-  Updates.emplace_back(DominatorTree::Insert, BB, DummyReturnBB);
-}
-
 bool AMDGPUUnifyDivergentExitNodesImpl::run(Function &F, DominatorTree *DT,
                                             const PostDominatorTree &PDT,
                                             const UniformityInfo &UA) {
+  assert(hasOnlySimpleTerminator(F) && "Unsupported block terminator.");
+
   if (PDT.root_size() == 0 ||
       (PDT.root_size() == 1 &&
-       !isa<BranchInst, CallBrInst>(PDT.getRoot()->getTerminator())))
+       !isa<BranchInst>(PDT.getRoot()->getTerminator())))
     return false;
 
   // Loop over all of the blocks in a function, tracking all of the blocks that
@@ -260,27 +222,46 @@ bool AMDGPUUnifyDivergentExitNodesImpl::run(Function &F, DominatorTree *DT,
       if (HasDivergentExitBlock)
         UnreachableBlocks.push_back(BB);
     } else if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator())) {
-      if (!DummyReturnBB)
-        DummyReturnBB = createDummyReturnBlock(F, ReturningBlocks);
+
+      ConstantInt *BoolTrue = ConstantInt::getTrue(F.getContext());
+      if (DummyReturnBB == nullptr) {
+        DummyReturnBB = BasicBlock::Create(F.getContext(),
+                                           "DummyReturnBlock", &F);
+        Type *RetTy = F.getReturnType();
+        Value *RetVal = RetTy->isVoidTy() ? nullptr : PoisonValue::get(RetTy);
+        ReturnInst::Create(F.getContext(), RetVal, DummyReturnBB);
+        ReturningBlocks.push_back(DummyReturnBB);
+      }
 
       if (BI->isUnconditional()) {
         BasicBlock *LoopHeaderBB = BI->getSuccessor(0);
         BI->eraseFromParent(); // Delete the unconditional branch.
         // Add a new conditional branch with a dummy edge to the return block.
-        BranchInst::Create(LoopHeaderBB, DummyReturnBB,
-                           ConstantInt::getTrue(F.getContext()), BB);
+        BranchInst::Create(LoopHeaderBB, DummyReturnBB, BoolTrue, BB);
+        Updates.emplace_back(DominatorTree::Insert, BB, DummyReturnBB);
+      } else { // Conditional branch.
+        SmallVector<BasicBlock *, 2> Successors(successors(BB));
+
+        // Create a new transition block to hold the conditional branch.
+        BasicBlock *TransitionBB = BB->splitBasicBlock(BI, "TransitionBlock");
+
+        Updates.reserve(Updates.size() + 2 * Successors.size() + 2);
+
+        // 'Successors' become successors of TransitionBB instead of BB,
+        // and TransitionBB becomes a single successor of BB.
+        Updates.emplace_back(DominatorTree::Insert, BB, TransitionBB);
+        for (BasicBlock *Successor : Successors) {
+          Updates.emplace_back(DominatorTree::Insert, TransitionBB, Successor);
+          Updates.emplace_back(DominatorTree::Delete, BB, Successor);
+        }
+
+        // Create a branch that will always branch to the transition block and
+        // references DummyReturnBB.
+        BB->getTerminator()->eraseFromParent();
+        BranchInst::Create(TransitionBB, DummyReturnBB, BoolTrue, BB);
         Updates.emplace_back(DominatorTree::Insert, BB, DummyReturnBB);
-      } else {
-        handleNBranch(F, BB, BI, DummyReturnBB, Updates);
       }
       Changed = true;
-    } else if (CallBrInst *CBI = dyn_cast<CallBrInst>(BB->getTerminator())) {
-      if (!DummyReturnBB)
-        DummyReturnBB = createDummyReturnBlock(F, ReturningBlocks);
-
-      handleNBranch(F, BB, CBI, DummyReturnBB, Updates);
-    } else {
-      llvm_unreachable("unsupported block terminator");
     }
   }
 
diff --git a/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp b/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
index 0a8f5ea2fdae1..5f6f66a4bc213 100644
--- a/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
+++ b/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
@@ -558,10 +558,11 @@ void StructurizeCFG::analyzeLoops(RegionNode *N) {
   } else {
     // Test for successors as back edge
     BasicBlock *BB = N->getNodeAs<BasicBlock>();
-    if (BranchInst *Term = dyn_cast<BranchInst>(BB->getTerminator()))
-      for (BasicBlock *Succ : Term->successors())
-        if (Visited.count(Succ))
-          Loops[Succ] = BB;
+    BranchInst *Term = cast<BranchInst>(BB->getTerminator());
+
+    for (BasicBlock *Succ : Term->successors())
+      if (Visited.count(Succ))
+        Loops[Succ] = BB;
   }
 }
 
@@ -593,7 +594,7 @@ void StructurizeCFG::gatherPredicates(RegionNode *N) {
 
   for (BasicBlock *P : predecessors(BB)) {
     // Ignore it if it's a branch from outside into our region entry
-    if (!ParentRegion->contains(P) || !dyn_cast<BranchInst>(P->getTerminator()))
+    if (!ParentRegion->contains(P))
       continue;
 
     Region *R = RI->getRegionFor(P);
@@ -1401,17 +1402,13 @@ bool StructurizeCFG::makeUniformRegion(Region *R, UniformityInfo &UA) {
 /// Run the transformation for each region found
 bool StructurizeCFG::run(Region *R, DominatorTree *DT,
                          const TargetTransformInfo *TTI) {
-  // CallBr and its corresponding direct target blocks are for now ignored by
-  // this pass. This is not a limitation for the currently intended uses cases
-  // of callbr in the AMDGPU backend.
-  // Parent and child regions are not affected by this (current) restriction.
-  // See `llvm/test/Transforms/StructurizeCFG/callbr.ll` for details.
-  if (R->isTopLevelRegion() || isa<CallBrInst>(R->getEntry()->getTerminator()))
+  if (R->isTopLevelRegion())
     return false;
 
   this->DT = DT;
   this->TTI = TTI;
   Func = R->getEntry()->getParent();
+  assert(hasOnlySimpleTerminator(*Func) && "Unsupported block terminator.");
 
   ParentRegion = R;
 
diff --git a/llvm/test/CodeGen/AMDGPU/callbr.ll b/llvm/test/CodeGen/AMDGPU/callbr.ll
deleted file mode 100644
index 253a6ec100eae..0000000000000
--- a/llvm/test/CodeGen/AMDGPU/callbr.ll
+++ /dev/null
@@ -1,54 +0,0 @@
-; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
-; RUN: llc -mtriple=amdgcn -mcpu=gfx90a < %s | FileCheck %s
-
-define void @callbr_inline_asm(ptr %src, ptr %dst1, ptr %dst2, i32 %c) {
-; CHECK-LABEL: callbr_inline_asm:
-; CHECK:       ; %bb.0:
-; CHECK-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; CHECK-NEXT:    flat_load_dword v0, v[0:1]
-; CHECK-NEXT:    ;;#ASMSTART
-; CHECK-NEXT:    v_cmp_gt_i32 vcc v6, 42; s_cbranch_vccnz .LBB0_2
-; CHECK-NEXT:    ;;#ASMEND
-; CHECK-NEXT:  ; %bb.1: ; %fallthrough
-; CHECK-NEXT:    s_waitcnt vmcnt(0) lgkmcnt(0)
-; CHECK-NEXT:    flat_store_dword v[2:3], v0
-; CHECK-NEXT:    s_waitcnt vmcnt(0) lgkmcnt(0)
-; CHECK-NEXT:    s_setpc_b64 s[30:31]
-; CHECK-NEXT:  .LBB0_2: ; Inline asm indirect target
-; CHECK-NEXT:    ; %indirect
-; CHECK-NEXT:    ; Label of block must be emitted
-; CHECK-NEXT:    s_waitcnt vmcnt(0) lgkmcnt(0)
-; CHECK-NEXT:    flat_store_dword v[4:5], v0
-; CHECK-NEXT:    s_waitcnt vmcnt(0) lgkmcnt(0)
-; CHECK-NEXT:    s_setpc_b64 s[30:31]
-	%a = load i32, ptr %src, align 4
-	callbr void asm "v_cmp_gt_i32 vcc $0, 42; s_cbranch_vccnz ${1:l}", "r,!i"(i32 %c) to label %fallthrough [label %indirect]
-fallthrough:
-	store i32 %a, ptr %dst1, align 4
-	br label %ret
-indirect:
-	store i32 %a, ptr %dst2, align 4
-	br label %ret
-ret:
-	ret void
-}
-
-define void @callbr_self_loop(i1 %c) {
-; CHECK-LABEL: callbr_self_loop:
-; CHECK:       ; %bb.0:
-; CHECK-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; CHECK-NEXT:  .LBB1_1: ; %callbr
-; CHECK-NEXT:    ; =>This Inner Loop Header: Depth=1
-; CHECK-NEXT:    ;;#ASMSTART
-; CHECK-NEXT:    ;;#ASMEND
-; CHECK-NEXT:    s_branch .LBB1_1
-; CHECK-NEXT:  .LBB1_2: ; Inline asm indirect target
-; CHECK-NEXT:    ; %callbr.target.ret
-; CHECK-NEXT:    ; Label of block must be emitted
-; CHECK-NEXT:    s_setpc_b64 s[30:31]
-  br label %callbr
-callbr:
-  callbr void asm "", "!i"() to label %callbr [label %ret]
-ret:
-  ret void
-}
diff --git a/llvm/test/CodeGen/AMDGPU/do-not-unify-divergent-exit-nodes-with-musttail.ll b/llvm/test/CodeGen/AMDGPU/do-not-unify-divergent-exit-nodes-with-musttail.ll
index 076a99ff8588f..007e3f0a6bdbc 100644
--- a/llvm/test/CodeGen/AMDGPU/do-not-unify-divergent-exit-nodes-with-musttail.ll
+++ b/llvm/test/CodeGen/AMDGPU/do-not-unify-divergent-exit-nodes-with-musttail.ll
@@ -3,7 +3,6 @@
 
 declare void @foo(ptr)
 declare i1 @bar(ptr)
-declare i32 @bar32(ptr)
 
 define void @musttail_call_without_return_value(ptr %p) {
 ; CHECK-LABEL: define void @musttail_call_without_return_value(
@@ -29,31 +28,6 @@ bb.1:
   ret void
 }
 
-define void @musttail_call_without_return_value_callbr(ptr %p) {
-; CHECK-LABEL: define void @musttail_call_without_return_value_callbr(
-; CHECK-SAME: ptr [[P:%.*]]) #[[ATTR0]] {
-; CHECK-NEXT:  [[ENTRY:.*:]]
-; CHECK-NEXT:    [[LOAD:%.*]] = load i32, ptr [[P]], align 1
-; CHECK-NEXT:    callbr void asm "", "r,!i"(i32 [[LOAD]])
-; CHECK-NEXT:            to label %[[BB_0:.*]] [label %bb.1]
-; CHECK:       [[BB_0]]:
-; CHECK-NEXT:    musttail call void @foo(ptr [[P]])
-; CHECK-NEXT:    ret void
-; CHECK:       [[BB_1:.*:]]
-; CHECK-NEXT:    ret void
-;
-entry:
-  %load = load i32, ptr %p, align 1
-  callbr void asm "", "r,!i"(i32 %load) to label %bb.0 [label %bb.1]
-
-bb.0:
-  musttail call void @foo(ptr %p)
-  ret void
-
-bb.1:
-  ret void
-}
-
 define i1 @musttail_call_with_return_value(ptr %p) {
 ; CHECK-LABEL: define i1 @musttail_call_with_return_value(
 ; CHECK-SAME: ptr [[P:%.*]]) #[[ATTR0]] {
@@ -77,28 +51,3 @@ bb.0:
 bb.1:
   ret i1 %load
 }
-
-define i32 @musttail_call_with_return_value_callbr(ptr %p) {
-; CHECK-LABEL: define i32 @musttail_call_with_return_value_callbr(
-; CHECK-SAME: ptr [[P:%.*]]) #[[ATTR0]] {
-; CHECK-NEXT:  [[ENTRY:.*:]]
-; CHECK-NEXT:    [[LOAD:%.*]] = load i32, ptr [[P]], align 1
-; CHECK-NEXT:    callbr void asm "", "r,!i"(i32 [[LOAD]])
-; CHECK-NEXT:            to label %[[BB_0:.*]] [label %bb.1]
-; CHECK:       [[BB_0]]:
-; CHECK-NEXT:    [[RET:%.*]] = musttail call i32 @bar32(ptr [[P]])
-; CHECK-NEXT:    ret i32 [[RET]]
-; CHECK:       [[BB_1:.*:]]
-; CHECK-NEXT:    ret i32 [[LOAD]]
-;
-entry:
-  %load = load i32, ptr %p, align 1
-  callbr void asm "", "r,!i"(i32 %load) to label %bb.0 [label %bb.1]
-
-bb.0:
-  %ret = musttail call i32 @bar32(ptr %p)
-  ret i32 %ret
-
-bb.1:
-  ret i32 %load
-}
diff --git a/llvm/test/CodeGen/AMDGPU/infinite-loop.ll b/llvm/test/CodeGen/AMDGPU/infinite-loop.ll
index df635925b87df..3e2e43faca5aa 100644
--- a/llvm/test/CodeGen/AMDGPU/infinite-loop.ll
+++ b/llvm/test/CodeGen/AMDGPU/infinite-loop.ll
@@ -36,60 +36,26 @@ loop:
   br label %loop
 }
 
-define amdgpu_kernel void @infinite_loop_callbr(ptr addrspace(1) %out) {
-; SI-LABEL: infinite_loop_callbr:
-; SI:       ; %bb.0: ; %entry
-; SI-NEXT:    s_load_dwordx2 s[0:1], s[4:5], 0x9
-; SI-NEXT:    ;;#ASMSTART
-; SI-NEXT:    ;;#ASMEND
-; SI-NEXT:    s_mov_b32 s3, 0xf000
-; SI-NEXT:    s_mov_b32 s2, -1
-; SI-NEXT:    v_mov_b32_e32 v0, 0x3e7
-; SI-NEXT:    s_waitcnt lgkmcnt(0)
-; SI-NEXT:    buffer_store_dword v0, off, s[0:3], 0
-; SI-NEXT:    s_waitcnt vmcnt(0)
-; SI-NEXT:    s_endpgm
-; IR-LABEL: @infinite_loop_callbr(
-; IR-NEXT:  entry:
-; IR-NEXT:    callbr void asm "", ""()
-; IR-NEXT:            to label [[LOOP:%.*]] []
-; IR:       loop:
-; IR-NEXT:    store volatile i32 999, ptr addrspace(1) [[OUT:%.*]], align 4
-; IR-NEXT:    br i1 true, label [[TRANSITIONBLOCK:%.*]], label [[DUMMYRETURNBLOCK:%.*]]
-; IR:       TransitionBlock:
-; IR-NEXT:    callbr void asm "", ""()
-; IR-NEXT:            to label [[LOOP]] []
-; IR:       DummyReturnBlock:
-; IR-NEXT:    ret void
-;
-entry:
-  callbr void asm "", ""() to label %loop []
-
-loop:
-  store volatile i32 999, ptr addrspace(1) %out, align 4
-  callbr void asm "", ""() to label %loop []
-}
-
 define amdgpu_kernel void @infinite_loop_ret(ptr addrspace(1) %out) {
 ; SI-LABEL: infinite_loop_ret:
 ; SI:       ; %bb.0: ; %entry
 ; SI-NEXT:    v_cmp_eq_u32_e32 vcc, 1, v0
 ; SI-NEXT:    s_and_saveexec_b64 s[0:1], vcc
-; SI-NEXT:    s_cbranch_execz .LBB2_3
+; SI-NEXT:    s_cbranch_execz .LBB1_3
 ; SI-NEXT:  ; %bb.1: ; %loop.preheader
 ; SI-NEXT:    s_load_dwordx2 s[0:1], s[4:5], 0x9
 ; SI-NEXT:    s_mov_b32 s3, 0xf000
 ; SI-NEXT:    s_mov_b32 s2, -1
 ; SI-NEXT:    v_mov_b32_e32 v0, 0x3e7
 ; SI-NEXT:    s_and_b64 vcc, exec, -1
-; SI-NEXT:  .LBB2_2: ; %loop
+; SI-NEXT:  .LBB1_2: ; %loop
 ; SI-NEXT:    ; =>This Inner Loop Header: Depth=1
 ; SI-NEXT:    s_waitcnt lgkmcnt(0)
 ; SI-NEXT:    buffer_store_dword v0, off, s[0:3], 0
 ; SI-NEXT:    s_waitcnt vmcnt(0)
 ; SI-NEXT:    s_mov_b64 vcc, vcc
-; SI-NEXT:    s_cbranch_vccnz .LBB2_2
-; SI-NEXT:  .LBB2_3: ; %UnifiedReturnBlock
+; SI-NEXT:    s_cbranch_vccnz .LBB1_2
+; SI-NEXT:  .LBB1_3: ; %UnifiedReturnBlock
 ; SI-NEXT:    s_endpgm
 ; IR-LABEL: @infinite_loop_ret(
 ; IR-NEXT:  entry:
@@ -115,93 +81,44 @@ return:
   ret void
 }
 
-define amdgpu_kernel void @infinite_loop_ret_callbr(ptr addrspace(1) %out) {
-; SI-LABEL: infinite_loop_ret_callbr:
-; SI:       ; %bb.0: ; %entry
-; SI-NEXT:    v_cmp_eq_u32_e32 vcc, 1, v0
-; SI-NEXT:    v_cndmask_b32_e64 v0, 0, 1, vcc
-; SI-NEXT:    ;;#ASMSTART
-; SI-NEXT:    ;;#ASMEND
-; SI-NEXT:  ; %bb.1: ; %loop.preheader
-; SI-NEXT:    s_load_dwordx2 s[0:1], s[4:5], 0x9
-; SI-NEXT:    s_mov_b32 s3, 0xf000
-; SI-NEXT:    s_mov_b32 s2, -1
-; SI-NEXT:    v_mov_b32_e32 v0, 0x3e7
-; SI-NEXT:    s_waitcnt lgkmcnt(0)
-; SI-NEXT:    buffer_store_dword v0, off, s[0:3], 0
-; SI-NEXT:    s_waitcnt vmcnt(0)
-; SI-NEXT:  .LBB3_2: ; Inline asm indirect target
-; SI-NEXT:    ; %UnifiedReturnBlock
-; SI-NEXT:    ; Label of block must be emitted
-; SI-NEXT:    s_endpgm
-; IR-LABEL: @infinite_loop_ret_callbr(
-; IR-NEXT:  entry:
-; IR-NEXT:    [[TMP:%.*]] = tail call i32 @llvm.amdgcn.workitem.id.x()
-; IR-NEXT:    [[COND:%.*]] = icmp eq i32 [[TMP]], 1
-; IR-NEXT:    [[COND32:%.*]] = zext i1 [[COND]] to i32
-; IR-NEXT:    callbr void asm "", "r,!i"(i32 [[COND32]])
-; IR-NEXT:            to label [[LOOP:%.*]] [label %UnifiedReturnBlock]
-; IR:       loop:
-; IR-NEXT:    store volatile i32 999, ptr addrspace(1) [[OUT:%.*]], align 4
-; IR-NEXT:    br i1 true, label [[TRANSITIONBLOCK:%.*]], label [[UNIFIEDRETURNBLOCK:%.*]]
-; IR:       TransitionBlock:
-; IR-NEXT:    callbr void asm "", ""()
-; IR-NEXT:            to label [[LOOP]] []
-; IR:       UnifiedReturnBlock:
-; IR-NEXT:    ret void
-;
-entry:
-  %tmp = tail call i32 @llvm.amdgcn.workitem.id.x()
-  %cond = icmp eq i32 %tmp, 1
-  %cond32 = zext i1 %cond to i32
-  callbr void asm "", "r,!i"(i32 %cond32) to label %loop [label %return]
-
-loop:
-  store volatile i32 999, ptr addrspace(1) %out, align 4
-  callbr void asm "", ""() to label %loop []
-
-return:
-  ret void
-}
-
 define amdgpu_kernel void @infinite_loops(ptr addrspace(1) %out) {
 ; SI-LABEL: infinite_loops:
 ; SI:       ; %bb.0: ; %entry
 ; SI-NEXT:    s_load_dwordx2 s[0:1], s[4:5], 0x9
 ; SI-NEXT:    s_mov_b64 s[2:3], -1
-; SI-NEXT:    s_cbranch_scc1 .LBB4_4
+; SI-NEXT:    s_cbranch_scc1 .LBB2_4
 ; SI-NEXT:  ; %bb.1:
 ; SI-NEXT:    s_mov_b32 s3, 0xf000
 ; SI-NEXT:    s_mov_b32 s2, -1
 ; SI-NEXT:    v_mov_b32_e32 v0, 0x378
 ; SI-NEXT:    s_and_b64 vcc, exec, -1
-; SI-NEXT:  .LBB4_2: ; %loop2
+; SI-NEXT:  .LBB2_2: ; %loop2
 ; SI-NEXT:    ; =>This Inner Loop Header: Depth=1
 ; SI-NEXT:    s_waitcnt lgkmcnt(0)
 ; SI-NEXT:    buffer_store_dword v0, off, s[0:3], 0
 ; SI-NEXT:    s_waitcnt vmcnt(0)
 ; SI-NEXT:    s_mov_b64 vcc, vcc
-; SI-NEXT:    s_cbranch_vccnz .LBB4_2
+; SI-NEXT:    s_cbranch_vccnz .LBB2_2
 ; SI-NEXT:  ; %bb.3: ; %Flow
 ; SI-NEXT:    s_mov_b64 s[2:3], 0
-; SI-NEXT:  .LBB4_4: ; %Flow2
+; SI-NEXT:  .LBB2_4: ; %Flow2
 ; SI-NEXT:    s_and_b64 vcc, exec, s[2:3]
 ; SI-NEXT:    s_waitcnt lgkmcnt(0)
 ; SI-NEXT:    s_mov_b64 vcc, vcc
-; SI-NEXT:    s_cbranch_vccz .LBB4_7
+; SI-NEXT:    s_cbranch_vccz .LBB2_7
 ; SI-NEXT:  ; %bb.5:
 ; SI-NEXT:    s_mov_b32 s3, 0xf000
 ; SI-NEXT:    s_mov_b32 s2, -1
 ; SI-NEXT:    s_waitcnt expcnt(0)
 ; SI-NEXT:    v_mov_b32_e32 v0, 0x3e7
 ; SI-NEXT:    s_and_b64 vcc, exec, 0
-; SI-NEXT:  .LBB4_6: ; %loop1
+; SI-NEXT:  .LBB2_6: ; %loop1
 ; SI-NEXT:    ; =>This Inner Loop Header: Depth=1
 ; SI-NEXT:    buffer_store_dword v0, off, s[0:3], 0
 ; SI-NEXT:    s_waitcnt vmcnt(0)
 ; SI-NEXT:    s_mov_b64 vcc, vcc
-; SI-NEXT:    s_cbranch_vccz .LBB4_6
-; SI-NEXT:  .LBB4_7: ; %DummyReturnBlock
+; SI-NEXT:    s_cbranch_vccz .LBB2_6
+; SI-NEXT:  .LBB2_7: ; %DummyReturnBlock
 ; SI-NEXT:    s_endpgm
 ; IR-LABEL: @infinite_loops(
 ; IR-NEXT:  entry:
@@ -227,78 +144,24 @@ loop2:
   br label %loop2
 }
 
-define amdgpu_kernel void @infinite_loops_callbr(ptr addrspace(1) %out) {
-; SI-LABEL: infinite_loops_callbr:
-; SI:       ; %bb.0: ; %entry
-; SI-NEXT:    s_load_dwordx2 s[0:1], s[4:5], 0x9
-; SI-NEXT:    s_waitcnt lgkmcnt(0)
-; SI-NEXT:    ;;#ASMSTART
-; SI-NEXT:    ;;#ASMEND
-; SI-NEXT:  ; %bb.1: ; %loop1
-; SI-NEXT:    s_mov_b32 s3, 0xf000
-; SI-NEXT:    s_mov_b32 s2, -1
-; SI-NEXT:    v_mov_b32_e32 v0, 0x3e7
-; SI-NEXT:    buffer_store_dword v0, off, s[0:3], 0
-; SI-NEXT:    s_waitcnt vmcnt(0)
-; SI-NEXT:    s_endpgm
-; SI-NEXT:  .LBB5_2: ; Inline asm indirect target
-; SI-NEXT:    ; %loop2.preheader
-; SI-NEXT:    ; Label of block must be emitted
-; SI-NEXT:    s_mov_b32 s3, 0xf000
-; SI-NEXT:    s_mov_b32 s2, -1
-; SI-NEXT:    v_mov_b32_e32 v0, 0x378
-; SI-NEXT:    buffer_store_dword v0, off, s[0:3], 0
-; SI-NEXT:    s_waitcnt vmcnt(0)
-; SI-NEXT:    s_endpgm
-; IR-LABEL: @infinite_loops_callbr(
-; IR-NEXT:  entry:
-; IR-NEXT:    callbr void asm "", "r,!i"(i32 poison)
-; IR-NEXT:            to label [[LOOP1:%.*]] [label %loop2]
-; IR:       loop1:
-; IR-NEXT:    store volatile i32 999, ptr addrspace(1) [[OUT:%.*]], align 4
-; IR-NEXT:    br i1 true, label [[TRANSITIONBLOCK:%.*]], label [[DUMMYRETURNBLOCK:%.*]]
-; IR:       TransitionBlock:
-; IR-NEXT:    callbr void asm "", ""()
-; IR-NEXT:            to label [[LOOP1]] []
-; IR:       loop2:
-; IR-NEXT:    store volatile i32 888, ptr addrspace(1) [[OUT]], align 4
-; IR-NEXT:    br i1 true, label [[TRANSITIONBLOCK1:%.*]], label [[DUMMYRETURNBLOCK]]
-; IR:       TransitionBlock1:
-; IR-NEXT:    callbr void asm "", ""()
-; IR-NEXT:            to label [[LOOP2:%.*]] []
-; IR:       DummyReturnBlock:
-; IR-NEXT:    ret void
-;
-entry:
-  callbr void asm "", "r,!i"(i32 poison) to label %loop1 [label %loop2]
-
-loop1:
-  store volatile i32 999, ptr addrspace(1) %out, align 4
-  callbr void asm "", ""() to label %loop1 []
...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/166186


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