From 00cb5b724547a821516292fe5cded7c6a5358bda Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Fri, 19 Feb 2010 18:12:07 +0000 Subject: [PATCH] Teach ScalarEvolution how to compute a tripcount for a loop with true or false as its exit condition. These are usually eliminated by SimplifyCFG, but the may be left around during a pass which wishes to preserve the CFG. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96683 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/ScalarEvolution.cpp | 13 ++++ test/Analysis/ScalarEvolution/trip-count10.ll | 76 +++++++++++++++++++ .../IndVarSimplify/2003-09-12-MultiplePred.ll | 2 +- .../2003-12-10-RemoveInstrCrash.ll | 2 +- .../IndVarSimplify/2003-12-15-Crash.ll | 4 +- .../IndVarSimplify/2005-11-18-Crash.ll | 2 +- .../IndVarSimplify/2006-12-10-BitCast.ll | 2 +- .../IndVarSimplify/2009-05-24-useafterfree.ll | 4 +- test/Transforms/IndVarSimplify/avoid-i0.ll | 4 +- test/Transforms/IndVarSimplify/max-pointer.ll | 4 +- 10 files changed, 101 insertions(+), 12 deletions(-) create mode 100644 test/Analysis/ScalarEvolution/trip-count10.ll diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index c2284a8ab9b..a0700ba4218 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -3703,6 +3703,19 @@ ScalarEvolution::ComputeBackedgeTakenCountFromExitCond(const Loop *L, if (ICmpInst *ExitCondICmp = dyn_cast(ExitCond)) return ComputeBackedgeTakenCountFromExitCondICmp(L, ExitCondICmp, TBB, FBB); + // Check for a constant condition. These are normally stripped out by + // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to + // preserve the CFG and is temporarily leaving constant conditions + // in place. + if (ConstantInt *CI = dyn_cast(ExitCond)) { + if (L->contains(FBB) == !CI->getZExtValue()) + // The backedge is always taken. + return getCouldNotCompute(); + else + // The backedge is never taken. + return getIntegerSCEV(0, CI->getType()); + } + // If it's not an integer or pointer comparison then compute it the hard way. return ComputeBackedgeTakenCountExhaustively(L, ExitCond, !L->contains(TBB)); } diff --git a/test/Analysis/ScalarEvolution/trip-count10.ll b/test/Analysis/ScalarEvolution/trip-count10.ll new file mode 100644 index 00000000000..0a992f952a8 --- /dev/null +++ b/test/Analysis/ScalarEvolution/trip-count10.ll @@ -0,0 +1,76 @@ +; RUN: opt < %s -analyze -scalar-evolution | FileCheck %s + +; Trip counts with trivial exit conditions. + +; CHECK: Determining loop execution counts for: @a +; CHECK: Loop %loop: Unpredictable backedge-taken count. +; CHECK: Loop %loop: Unpredictable max backedge-taken count. + +; CHECK: Determining loop execution counts for: @b +; CHECK: Loop %loop: backedge-taken count is false +; CHECK: Loop %loop: max backedge-taken count is false + +; CHECK: Determining loop execution counts for: @c +; CHECK: Loop %loop: backedge-taken count is false +; CHECK: Loop %loop: max backedge-taken count is false + +; CHECK: Determining loop execution counts for: @d +; CHECK: Loop %loop: Unpredictable backedge-taken count. +; CHECK: Loop %loop: Unpredictable max backedge-taken count. + +define void @a(i64 %n) nounwind { +entry: + %t0 = icmp sgt i64 %n, 0 + br i1 %t0, label %loop, label %return + +loop: + %i = phi i64 [ %i.next, %loop ], [ 0, %entry ] + %i.next = add nsw i64 %i, 1 + %exitcond = icmp eq i64 %i.next, %n + br i1 false, label %return, label %loop + +return: + ret void +} +define void @b(i64 %n) nounwind { +entry: + %t0 = icmp sgt i64 %n, 0 + br i1 %t0, label %loop, label %return + +loop: + %i = phi i64 [ %i.next, %loop ], [ 0, %entry ] + %i.next = add nsw i64 %i, 1 + %exitcond = icmp eq i64 %i.next, %n + br i1 true, label %return, label %loop + +return: + ret void +} +define void @c(i64 %n) nounwind { +entry: + %t0 = icmp sgt i64 %n, 0 + br i1 %t0, label %loop, label %return + +loop: + %i = phi i64 [ %i.next, %loop ], [ 0, %entry ] + %i.next = add nsw i64 %i, 1 + %exitcond = icmp eq i64 %i.next, %n + br i1 false, label %loop, label %return + +return: + ret void +} +define void @d(i64 %n) nounwind { +entry: + %t0 = icmp sgt i64 %n, 0 + br i1 %t0, label %loop, label %return + +loop: + %i = phi i64 [ %i.next, %loop ], [ 0, %entry ] + %i.next = add nsw i64 %i, 1 + %exitcond = icmp eq i64 %i.next, %n + br i1 true, label %loop, label %return + +return: + ret void +} diff --git a/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll b/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll index 36d50065d37..30d9ea6fb3c 100644 --- a/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll +++ b/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll @@ -7,7 +7,7 @@ define i32 @test() { LoopHead: ; preds = %LoopHead, %0, %0 %A = phi i32 [ 7, %0 ], [ 7, %0 ], [ %B, %LoopHead ] ; [#uses=1] %B = add i32 %A, 1 ; [#uses=2] - br i1 false, label %LoopHead, label %Out + br i1 undef, label %LoopHead, label %Out Out: ; preds = %LoopHead ret i32 %B diff --git a/test/Transforms/IndVarSimplify/2003-12-10-RemoveInstrCrash.ll b/test/Transforms/IndVarSimplify/2003-12-10-RemoveInstrCrash.ll index 70ea11ebf04..75363314750 100644 --- a/test/Transforms/IndVarSimplify/2003-12-10-RemoveInstrCrash.ll +++ b/test/Transforms/IndVarSimplify/2003-12-10-RemoveInstrCrash.ll @@ -10,7 +10,7 @@ no_exit: ; preds = %no_exit, %entry %k.0.pn = phi i32 [ %inc.4, %no_exit ], [ 1, %entry ] ; [#uses=1] %inc.3 = add i32 %j.0.pn, 1 ; [#uses=1] %inc.4 = add i32 %k.0.pn, 1 ; [#uses=1] - br i1 false, label %no_exit, label %loopexit + br i1 undef, label %no_exit, label %loopexit loopexit: ; preds = %no_exit, %entry ret void diff --git a/test/Transforms/IndVarSimplify/2003-12-15-Crash.ll b/test/Transforms/IndVarSimplify/2003-12-15-Crash.ll index 5aa2d90a42b..662828c749d 100644 --- a/test/Transforms/IndVarSimplify/2003-12-15-Crash.ll +++ b/test/Transforms/IndVarSimplify/2003-12-15-Crash.ll @@ -8,7 +8,7 @@ cond_continue.3: ; preds = %entry loopexit.14: ; preds = %entry %tmp.738 = sub i32 0, 0 ; [#uses=1] - br i1 false, label %no_exit.15.preheader, label %loopexit.15 + br i1 undef, label %no_exit.15.preheader, label %loopexit.15 no_exit.15.preheader: ; preds = %loopexit.14 br label %no_exit.15 @@ -16,7 +16,7 @@ no_exit.15.preheader: ; preds = %loopexit.14 no_exit.15: ; preds = %no_exit.15, %no_exit.15.preheader %highC.0 = phi i32 [ %tmp.738, %no_exit.15.preheader ], [ %dec.0, %no_exit.15 ] ; [#uses=1] %dec.0 = add i32 %highC.0, -1 ; [#uses=1] - br i1 false, label %no_exit.15, label %loopexit.15 + br i1 undef, label %no_exit.15, label %loopexit.15 loopexit.15: ; preds = %no_exit.15, %loopexit.14 ret void diff --git a/test/Transforms/IndVarSimplify/2005-11-18-Crash.ll b/test/Transforms/IndVarSimplify/2005-11-18-Crash.ll index f9a3fe6233a..7202c7ae9d8 100644 --- a/test/Transforms/IndVarSimplify/2005-11-18-Crash.ll +++ b/test/Transforms/IndVarSimplify/2005-11-18-Crash.ll @@ -9,7 +9,7 @@ entry: no_exit.0: ; preds = %no_exit.0, %entry %p.0.0 = phi i32* [ getelementptr ([29 x [29 x [2 x i32]]]* @fixtab, i32 0, i32 0, i32 0, i32 0), %entry ], [ %inc.0, %no_exit.0 ] ; [#uses=1] %inc.0 = getelementptr i32* %p.0.0, i32 1 ; [#uses=1] - br i1 false, label %no_exit.0, label %no_exit.1 + br i1 undef, label %no_exit.0, label %no_exit.1 no_exit.1: ; preds = %no_exit.0 ret void diff --git a/test/Transforms/IndVarSimplify/2006-12-10-BitCast.ll b/test/Transforms/IndVarSimplify/2006-12-10-BitCast.ll index 79ac1f072de..80c9ebf2f01 100644 --- a/test/Transforms/IndVarSimplify/2006-12-10-BitCast.ll +++ b/test/Transforms/IndVarSimplify/2006-12-10-BitCast.ll @@ -20,7 +20,7 @@ cond_next182.i: ; preds = %cond_next182.i, %cond_true52 %tmp194.i53 = bitcast i32 %decay.i.0 to float ; [#uses=1] %tmp195.i = fsub float %tmp194.i53, 8.000000e+00 ; [#uses=1] %tmp195.i.upgrd.1 = bitcast float %tmp195.i to i32 ; [#uses=1] - br i1 false, label %cond_next182.i, label %bb418.i.preheader + br i1 undef, label %cond_next182.i, label %bb418.i.preheader bb418.i.preheader: ; preds = %cond_next182.i ret void diff --git a/test/Transforms/IndVarSimplify/2009-05-24-useafterfree.ll b/test/Transforms/IndVarSimplify/2009-05-24-useafterfree.ll index 9ad86913e22..d73eee812b3 100644 --- a/test/Transforms/IndVarSimplify/2009-05-24-useafterfree.ll +++ b/test/Transforms/IndVarSimplify/2009-05-24-useafterfree.ll @@ -12,7 +12,7 @@ bb.nph1.preheader: ; preds = %4 br label %bb.nph1 bb.nph1: ; preds = %.outer, %bb.nph1.preheader - br i1 false, label %bb.nph3.preheader, label %.outer + br i1 undef, label %bb.nph3.preheader, label %.outer bb.nph3.preheader: ; preds = %bb.nph1 br label %bb.nph3 @@ -31,7 +31,7 @@ bb.nph3: ; preds = %bb.nph3, %bb.nph3.preheader br label %.outer .outer: ; preds = %.outer.loopexit, %bb.nph1 - br i1 false, label %bb.nph1, label %.outer._crit_edge.loopexit + br i1 undef, label %bb.nph1, label %.outer._crit_edge.loopexit .outer._crit_edge.loopexit: ; preds = %.outer br label %.outer._crit_edge diff --git a/test/Transforms/IndVarSimplify/avoid-i0.ll b/test/Transforms/IndVarSimplify/avoid-i0.ll index d110a8a7ba9..59661fa2e88 100644 --- a/test/Transforms/IndVarSimplify/avoid-i0.ll +++ b/test/Transforms/IndVarSimplify/avoid-i0.ll @@ -10,13 +10,13 @@ entry: bb: ; preds = %bb6, %entry %p_71_addr.0 = phi i8 [ %p_71, %entry ], [ %0, %bb6 ] ; [#uses=0] - br i1 false, label %bb4, label %bb1 + br i1 undef, label %bb4, label %bb1 bb1: ; preds = %bb ret i32 0 bb4: ; preds = %bb4, %bb - br i1 false, label %bb6, label %bb4 + br i1 undef, label %bb6, label %bb4 bb6: ; preds = %bb4 %0 = and i8 0, 0 ; [#uses=1] diff --git a/test/Transforms/IndVarSimplify/max-pointer.ll b/test/Transforms/IndVarSimplify/max-pointer.ll index 71bc720d5e9..f18f968f595 100644 --- a/test/Transforms/IndVarSimplify/max-pointer.ll +++ b/test/Transforms/IndVarSimplify/max-pointer.ll @@ -16,7 +16,7 @@ bb2: ; preds = %bb2, %entry %str2Ptr_addr.1 = phi i8* [ %str2Ptr_addr.0, %entry ], [ %1, %bb2 ] ; [#uses=1] %1 = getelementptr i8* %str2Ptr_addr.1, i64 1 ; [#uses=2] %2 = icmp ult i8* %1, %inLastBytePtr ; [#uses=0] - br i1 false, label %bb2, label %return + br i1 undef, label %bb2, label %return return: ; preds = %bb2 ret void @@ -32,7 +32,7 @@ bb2: ; preds = %bb2, %entry %str2Ptr_addr.1 = phi i8* [ %str2Ptr_addr.0, %entry ], [ %1, %bb2 ] ; [#uses=1] %1 = getelementptr i8* %str2Ptr_addr.1, i64 1 ; [#uses=2] %2 = icmp slt i8* %1, %inLastBytePtr ; [#uses=0] - br i1 false, label %bb2, label %return + br i1 undef, label %bb2, label %return return: ; preds = %bb2 ret void