FoldBranchToCommonDest merges branches into a single branch with or/and of the condit...

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194524 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index d56bb32..ff50b12 100644 (file)
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -2090,8 +2090,13 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) {
     // Ensure that any values used in the bonus instruction are also used
     // by the terminator of the predecessor.  This means that those values
     // must already have been resolved, so we won't be inhibiting the
-    // out-of-order core by speculating them earlier.
-    if (BonusInst) {
+    // out-of-order core by speculating them earlier. We also allow
+    // instructions that are used by the terminator's condition because it
+    // exposes more merging opportunities.
+    bool UsedByBranch = (BonusInst && BonusInst->hasOneUse() &&
+                         *BonusInst->use_begin() == Cond);
+
+    if (BonusInst && !UsedByBranch) {
       // Collect the values used by the bonus inst
       SmallPtrSet<Value*, 4> UsedValues;
       for (Instruction::op_iterator OI = BonusInst->op_begin(),

diff --git a/test/Transforms/SimplifyCFG/common-dest-folding.ll b/test/Transforms/SimplifyCFG/common-dest-folding.ll
index 10fb7d4..0aa3b2c 100644 (file)
--- a/test/Transforms/SimplifyCFG/common-dest-folding.ll
+++ b/test/Transforms/SimplifyCFG/common-dest-folding.ll
@@ -25,4 +25,33 @@ define i32 @foo(i32 %k, i32 %c1, i32 %c2) {
   ret i32 undef
 }
 
+;CHECK: @conduse
+;CHECK: shl i32 1, %c1
+;CHECK-NEXT: shl i32 1, %c2
+;CHECK-NEXT: and i32
+;CHECK-NEXT: icmp eq i32
+;CHECK-NEXT: and i32
+;CHECK-NEXT: icmp eq i32
+;CHECK: ret
+define i32 @conduse(i32 %k, i32 %c1, i32 %c2) #0 {
+bb:
+  %tmp = shl i32 1, %c1
+  %tmp4 = shl i32 1, %c2
+  %tmp1 = and i32 %tmp, %k
+  %tmp2 = icmp eq i32 %tmp1, 0
+  br i1 %tmp2, label %bb9, label %bb3
+
+bb3:                                              ; preds = %bb
+  %tmp5 = and i32 %tmp4, %k
+  %tmp6 = icmp eq i32 %tmp5, 0
+  br i1 %tmp6, label %bb9, label %bb7
+
+bb7:                                              ; preds = %bb3
+  %tmp8 = tail call i32 (...)* @bar() #1
+  br label %bb9
+
+bb9:                                              ; preds = %bb7, %bb3, %bb
+  ret i32 undef
+}
+
 declare i32 @bar(...)