[PATCH] D140166: [IR] return nullptr in Instruction::getInsertionPointAfterDef for CallBrInst

[Nick Desaulniers via Phabricator via llvm-commits]

nickdesaulniers updated this revision to Diff 489927.
nickdesaulniers marked 3 inline comments as done.
nickdesaulniers added a comment.
This revision is now accepted and ready to land.

- delay check for callbr inst, as per @StephenTozer


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D140166/new/

https://reviews.llvm.org/D140166

Files:
  llvm/lib/IR/Instruction.cpp
  llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
  llvm/test/Transforms/Coroutines/coro-debug.ll
  llvm/test/Transforms/InstCombine/freeze.ll
  llvm/test/Transforms/Reassociate/callbr.ll


Index: llvm/test/Transforms/Reassociate/callbr.ll
===================================================================
--- llvm/test/Transforms/Reassociate/callbr.ll
+++ llvm/test/Transforms/Reassociate/callbr.ll
@@ -6,8 +6,10 @@
 ; CHECK-NEXT:    [[RES:%.*]] = callbr i32 asm "", "=r,!i"()
 ; CHECK-NEXT:    to label [[NORMAL:%.*]] [label %abnormal]
 ; CHECK:       normal:
-; CHECK-NEXT:    [[FACTOR:%.*]] = mul i32 [[RES]], -2
-; CHECK-NEXT:    [[SUB2:%.*]] = add i32 [[FACTOR]], 5
+; CHECK-NEXT:    [[RES_NEG:%.*]] = sub i32 0, [[RES]]
+; CHECK-NEXT:    [[SUB1:%.*]] = add i32 [[RES_NEG]], 5
+; CHECK-NEXT:    [[RES_NEG1:%.*]] = sub i32 0, [[RES]]
+; CHECK-NEXT:    [[SUB2:%.*]] = add i32 [[SUB1]], [[RES_NEG1]]
 ; CHECK-NEXT:    ret i32 [[SUB2]]
 ; CHECK:       abnormal:
 ; CHECK-NEXT:    ret i32 0
Index: llvm/test/Transforms/InstCombine/freeze.ll
===================================================================
--- llvm/test/Transforms/InstCombine/freeze.ll
+++ llvm/test/Transforms/InstCombine/freeze.ll
@@ -453,9 +453,9 @@
 ; CHECK-NEXT:    to label [[CALLBR_CONT:%.*]] []
 ; CHECK:       callbr.cont:
 ; CHECK-NEXT:    [[PHI:%.*]] = phi i32 [ [[X]], [[ENTRY:%.*]] ], [ 0, [[CALLBR_CONT]] ]
+; CHECK-NEXT:    call void @use_i32(i32 [[X]])
 ; CHECK-NEXT:    [[FR:%.*]] = freeze i32 [[X]]
 ; CHECK-NEXT:    call void @use_i32(i32 [[FR]])
-; CHECK-NEXT:    call void @use_i32(i32 [[FR]])
 ; CHECK-NEXT:    call void @use_i32(i32 [[PHI]])
 ; CHECK-NEXT:    br label [[CALLBR_CONT]]
 ;
Index: llvm/test/Transforms/Coroutines/coro-debug.ll
===================================================================
--- llvm/test/Transforms/Coroutines/coro-debug.ll
+++ llvm/test/Transforms/Coroutines/coro-debug.ll
@@ -193,7 +193,8 @@
 ; CHECK: %[[CALLBR_RES:.+]] = callbr i32 asm
 ; CHECK-NEXT: to label %[[DEFAULT_DEST:.+]] [label
 ; CHECK: [[DEFAULT_DEST]]:
-; CHECK-NEXT: call void @llvm.dbg.declare(metadata i32 %[[CALLBR_RES]]
+; CHECK-NOT: {{.*}}:
+; CHECK: call void @llvm.dbg.declare(metadata i32 %[[CALLBR_RES]]
 ; CHECK: define internal fastcc void @f.destroy(%f.Frame* noundef nonnull align 8 dereferenceable(40) %FramePtr) #0 personality i32 0 !dbg ![[DESTROY:[0-9]+]]
 ; CHECK: define internal fastcc void @f.cleanup(%f.Frame* noundef nonnull align 8 dereferenceable(40) %FramePtr) #0 personality i32 0 !dbg ![[CLEANUP:[0-9]+]]
 
Index: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3370,7 +3370,8 @@
 }
 
 /// If the callee is a constexpr cast of a function, attempt to move the cast to
-/// the arguments of the call/callbr/invoke.
+/// the arguments of the call/invoke.
+/// CallBrInst is not supported.
 bool InstCombinerImpl::transformConstExprCastCall(CallBase &Call) {
   auto *Callee =
       dyn_cast<Function>(Call.getCalledOperand()->stripPointerCasts());
@@ -3422,7 +3423,11 @@
         return false;   // Attribute not compatible with transformed value.
     }
 
-    // If the callbase is an invoke/callbr instruction, and the return value is
+    // CallBr's don't have a single point after a def to insert at.
+    if (isa<CallBrInst>(Call))
+      return false;
+
+    // If the callbase is an invoke instruction, and the return value is
     // used by a PHI node in a successor, we cannot change the return type of
     // the call because there is no place to put the cast instruction (without
     // breaking the critical edge).  Bail out in this case.
@@ -3430,8 +3435,6 @@
       BasicBlock *PhisNotSupportedBlock = nullptr;
       if (auto *II = dyn_cast<InvokeInst>(Caller))
         PhisNotSupportedBlock = II->getNormalDest();
-      if (auto *CB = dyn_cast<CallBrInst>(Caller))
-        PhisNotSupportedBlock = CB->getDefaultDest();
       if (PhisNotSupportedBlock)
         for (User *U : Caller->users())
           if (PHINode *PN = dyn_cast<PHINode>(U))
Index: llvm/lib/IR/Instruction.cpp
===================================================================
--- llvm/lib/IR/Instruction.cpp
+++ llvm/lib/IR/Instruction.cpp
@@ -138,8 +138,9 @@
     InsertBB = II->getNormalDest();
     InsertPt = InsertBB->getFirstInsertionPt();
   } else if (auto *CB = dyn_cast<CallBrInst>(this)) {
-    InsertBB = CB->getDefaultDest();
-    InsertPt = InsertBB->getFirstInsertionPt();
+    // Def is available in multiple successors, there's no single dominating
+    // insertion point.
+    return nullptr;
   } else {
     assert(!isTerminator() && "Only invoke/callbr terminators return value");
     InsertBB = getParent();


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