Index: lib/Analysis/MustExecute.cpp =================================================================== --- lib/Analysis/MustExecute.cpp +++ lib/Analysis/MustExecute.cpp @@ -70,6 +70,11 @@ auto *BI = dyn_cast(CondExitBlock->getTerminator()); if (!BI || !BI->isConditional()) return false; + // If condition is constant and false leads to ExitBlock then we always + // execute the true branch. + if (auto *Cond = dyn_cast(BI->getCondition())) + if (BI->getSuccessor(Cond->getZExtValue() ? 1 : 0) == ExitBlock) + return true; auto *Cond = dyn_cast(BI->getCondition()); if (!Cond) return false; Index: test/Analysis/MustExecute/const-cond.ll =================================================================== --- /dev/null +++ test/Analysis/MustExecute/const-cond.ll @@ -0,0 +1,44 @@ +; NOTE: Assertions have been autogenerated by utils/update_test_checks.py +; RUN: opt -disable-output -print-mustexecute %s 2>&1 | FileCheck %s + +define i1 @const_cond(i32 %high) { +; CHECK-LABEL: @const_cond( +; CHECK-NEXT: entry: +; CHECK-NEXT: br label [[LOOP:%.*]] +; CHECK: loop: +; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ] ; (mustexec in: loop) +; CHECK-NEXT: br i1 true, label [[NEXT:%.*]], label [[NEVER1:%.*]] ; (mustexec in: loop) +; CHECK: next: +; CHECK-NEXT: br i1 false, label [[NEVER2:%.*]], label [[BACKEDGE]] ; (mustexec in: loop) +; CHECK: backedge: +; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i32 [[IV]], 1 ; (mustexec in: loop) +; CHECK-NEXT: [[EXIT_TEST:%.*]] = icmp slt i32 [[IV]], [[HIGH:%.*]] ; (mustexec in: loop) +; CHECK-NEXT: br i1 [[EXIT_TEST]], label [[LOOP]], label [[EXIT:%.*]] ; (mustexec in: loop) +; CHECK: exit: +; CHECK-NEXT: ret i1 false +; CHECK: never1: +; CHECK-NEXT: unreachable +; CHECK: never2: +; CHECK-NEXT: unreachable +; +entry: + br label %loop + +loop: + %iv = phi i32 [0, %entry], [%iv.next, %backedge] + br i1 true, label %next, label %never1 +next: + br i1 false, label %never2, label %backedge +backedge: + %iv.next = add nsw nuw i32 %iv, 1 + %exit.test = icmp slt i32 %iv, %high + br i1 %exit.test, label %loop, label %exit + +exit: + ret i1 false +never1: + unreachable +never2: + unreachable +} + Index: test/Transforms/LICM/hoist-mustexec.ll =================================================================== --- test/Transforms/LICM/hoist-mustexec.ll +++ test/Transforms/LICM/hoist-mustexec.ll @@ -218,6 +218,9 @@ define i32 @test-wrongphi(i32* noalias nocapture readonly %a) nounwind uwtable { ; CHECK-LABEL: @test-wrongphi( entry: +; CHECK-LABEL: entry +; CHECK: %i1 = load i32, i32* %a, align 4 +; CHECK-NEXT: br label %for.body br label %for.body for.body: @@ -230,7 +233,7 @@ br i1 %r.chk, label %fail, label %continue continue: ; CHECK-LABEL: continue -; CHECK: %i1 = load i32, i32* %a, align 4 +; CHECK-NOT: %i1 = load i32, i32* %a, align 4 %i1 = load i32, i32* %a, align 4 %add = add nsw i32 %i1, %acc %inc = add nuw nsw i32 %iv, 1