[llvm] 5986559 - [SimplifyCFG] Guard branch folding by speculate blocks flag
Teresa Johnson via llvm-commits
llvm-commits at lists.llvm.org
Tue Jul 25 06:46:45 PDT 2023
Author: Teresa Johnson
Date: 2023-07-25T06:46:19-07:00
New Revision: 5986559caa400ba6d977fb9d2224b79b52968b8e
URL: https://github.com/llvm/llvm-project/commit/5986559caa400ba6d977fb9d2224b79b52968b8e
DIFF: https://github.com/llvm/llvm-project/commit/5986559caa400ba6d977fb9d2224b79b52968b8e.diff
LOG: [SimplifyCFG] Guard branch folding by speculate blocks flag
Guard FoldBranchToCommonDest in SimplifyCFG with the SpeculateBlocks
flag as it can also speculate instructions.
This was split out of D155997.
Differential Revision: https://reviews.llvm.org/D156194
Added:
Modified:
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/test/Transforms/SimplifyCFG/speculate-blocks.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index d3a9a41aef1533..1d4cb851da4a21 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -6978,7 +6978,8 @@ bool SimplifyCFGOpt::simplifyUncondBranch(BranchInst *BI,
// branches to us and our successor, fold the comparison into the
// predecessor and use logical operations to update the incoming value
// for PHI nodes in common successor.
- if (FoldBranchToCommonDest(BI, DTU, /*MSSAU=*/nullptr, &TTI,
+ if (Options.SpeculateBlocks &&
+ FoldBranchToCommonDest(BI, DTU, /*MSSAU=*/nullptr, &TTI,
Options.BonusInstThreshold))
return requestResimplify();
return false;
@@ -7048,7 +7049,8 @@ bool SimplifyCFGOpt::simplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
// If this basic block is ONLY a compare and a branch, and if a predecessor
// branches to us and one of our successors, fold the comparison into the
// predecessor and use logical operations to pick the right destination.
- if (FoldBranchToCommonDest(BI, DTU, /*MSSAU=*/nullptr, &TTI,
+ if (Options.SpeculateBlocks &&
+ FoldBranchToCommonDest(BI, DTU, /*MSSAU=*/nullptr, &TTI,
Options.BonusInstThreshold))
return requestResimplify();
diff --git a/llvm/test/Transforms/SimplifyCFG/speculate-blocks.ll b/llvm/test/Transforms/SimplifyCFG/speculate-blocks.ll
index 9921942bbdea1a..07eac90186ef62 100644
--- a/llvm/test/Transforms/SimplifyCFG/speculate-blocks.ll
+++ b/llvm/test/Transforms/SimplifyCFG/speculate-blocks.ll
@@ -27,3 +27,54 @@ bb2:
%r = phi i32 [ 2, %entry ], [ 5, %bb ]
ret i32 %r
}
+
+define void @fold_branch_to_common_dest(i8 %v0, i8 %v1) {
+; YES-LABEL: define void @fold_branch_to_common_dest
+; YES-SAME: (i8 [[V0:%.*]], i8 [[V1:%.*]]) {
+; YES-NEXT: pred:
+; YES-NEXT: [[C0:%.*]] = icmp eq i8 [[V0]], 0
+; YES-NEXT: [[C1:%.*]] = icmp eq i8 [[V1]], 0
+; YES-NEXT: [[OR_COND:%.*]] = select i1 [[C0]], i1 [[C1]], i1 false
+; YES-NEXT: br i1 [[OR_COND]], label [[FINAL_LEFT:%.*]], label [[FINAL_RIGHT:%.*]]
+; YES: common.ret:
+; YES-NEXT: ret void
+; YES: final_left:
+; YES-NEXT: call void @sideeffect0()
+; YES-NEXT: br label [[COMMON_RET:%.*]]
+; YES: final_right:
+; YES-NEXT: call void @sideeffect1()
+; YES-NEXT: br label [[COMMON_RET]]
+;
+; NO-LABEL: define void @fold_branch_to_common_dest
+; NO-SAME: (i8 [[V0:%.*]], i8 [[V1:%.*]]) {
+; NO-NEXT: pred:
+; NO-NEXT: [[C0:%.*]] = icmp eq i8 [[V0]], 0
+; NO-NEXT: br i1 [[C0]], label [[DISPATCH:%.*]], label [[FINAL_RIGHT:%.*]]
+; NO: dispatch:
+; NO-NEXT: [[C1:%.*]] = icmp eq i8 [[V1]], 0
+; NO-NEXT: br i1 [[C1]], label [[FINAL_LEFT:%.*]], label [[FINAL_RIGHT]]
+; NO: common.ret:
+; NO-NEXT: ret void
+; NO: final_left:
+; NO-NEXT: call void @sideeffect0()
+; NO-NEXT: br label [[COMMON_RET:%.*]]
+; NO: final_right:
+; NO-NEXT: call void @sideeffect1()
+; NO-NEXT: br label [[COMMON_RET]]
+;
+pred:
+ %c0 = icmp eq i8 %v0, 0
+ br i1 %c0, label %dispatch, label %final_right
+dispatch:
+ %c1 = icmp eq i8 %v1, 0
+ br i1 %c1, label %final_left, label %final_right
+final_left:
+ call void @sideeffect0()
+ ret void
+final_right:
+ call void @sideeffect1()
+ ret void
+}
+
+declare void @sideeffect0()
+declare void @sideeffect1()
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