make instcombine's instruction sinking more aggressive in the

presence of PHI nodes.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84103 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 47 insertions, 4 deletions

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 88421db826..50d6d99e9b 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -12836,7 +12836,15 @@ bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
     // See if we can trivially sink this instruction to a successor basic block.
     if (I->hasOneUse()) {
       BasicBlock *BB = I->getParent();
-      BasicBlock *UserParent = cast<Instruction>(I->use_back())->getParent();
+      Instruction *UserInst = cast<Instruction>(I->use_back());
+      BasicBlock *UserParent;
+      
+      // Get the block the use occurs in.
+      if (PHINode *PN = dyn_cast<PHINode>(UserInst))
+        UserParent = PN->getIncomingBlock(I->use_begin().getUse());
+      else
+        UserParent = UserInst->getParent();
+      
       if (UserParent != BB) {
         bool UserIsSuccessor = false;
         // See if the user is one of our successors.
@@ -12849,8 +12857,7 @@ bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
         // If the user is one of our immediate successors, and if that successor
         // only has us as a predecessors (we'd have to split the critical edge
         // otherwise), we can keep going.
-        if (UserIsSuccessor && !isa<PHINode>(I->use_back()) &&
-            next(pred_begin(UserParent)) == pred_end(UserParent))
+        if (UserIsSuccessor && UserParent->getSinglePredecessor())
           // Okay, the CFG is simple enough, try to sink this instruction.
           MadeIRChange |= TryToSinkInstruction(I, UserParent);
       }
diff --git a/test/Transforms/InstCombine/sink_instruction.ll b/test/Transforms/InstCombine/sink_instruction.ll
index c46d210548..e521de208f 100644
--- a/test/Transforms/InstCombine/sink_instruction.ll
+++ b/test/Transforms/InstCombine/sink_instruction.ll
@@ -3,7 +3,8 @@
 ;; This tests that the instructions in the entry blocks are sunk into each
 ;; arm of the 'if'.
 
-define i32 @foo(i1 %C, i32 %A, i32 %B) {
+define i32 @test1(i1 %C, i32 %A, i32 %B) {
+; CHECK: @test1
 entry:
         %tmp.2 = sdiv i32 %A, %B                ; <i32> [#uses=1]
         %tmp.9 = add i32 %B, %A         ; <i32> [#uses=1]
@@ -18,3 +19,38 @@ endif:          ; preds = %entry
         ret i32 %tmp.2
 }
 
+
+;; PHI use, sink divide before call.
+define i32 @test2(i32 %x) nounwind ssp {
+; CHECK: @test2
+; CHECK-NOT: sdiv i32
+entry:
+  br label %bb
+
+bb:                                               ; preds = %bb2, %entry
+  %x_addr.17 = phi i32 [ %x, %entry ], [ %x_addr.0, %bb2 ] ; <i32> [#uses=4]
+  %i.06 = phi i32 [ 0, %entry ], [ %4, %bb2 ]     ; <i32> [#uses=1]
+  %0 = add nsw i32 %x_addr.17, 1                  ; <i32> [#uses=1]
+  %1 = sdiv i32 %0, %x_addr.17                    ; <i32> [#uses=1]
+  %2 = icmp eq i32 %x_addr.17, 0                  ; <i1> [#uses=1]
+  br i1 %2, label %bb1, label %bb2
+
+bb1:                                              ; preds = %bb
+; CHECK: bb1:
+; CHECK-NEXT: add nsw i32 %x_addr.17, 1
+; CHECK-NEXT: sdiv i32
+; CHECK-NEXT: tail call i32 @bar()
+  %3 = tail call i32 @bar() nounwind       ; <i32> [#uses=0]
+  br label %bb2
+
+bb2:                                              ; preds = %bb, %bb1
+  %x_addr.0 = phi i32 [ %1, %bb1 ], [ %x_addr.17, %bb ] ; <i32> [#uses=2]
+  %4 = add nsw i32 %i.06, 1                       ; <i32> [#uses=2]
+  %exitcond = icmp eq i32 %4, 1000000             ; <i1> [#uses=1]
+  br i1 %exitcond, label %bb4, label %bb
+
+bb4:                                              ; preds = %bb2
+  ret i32 %x_addr.0
+}
+
+declare i32 @bar()