diff options
| -rw-r--r-- | llvm/include/llvm/Analysis/ScalarEvolution.h | 7 | ||||
| -rw-r--r-- | llvm/lib/Transforms/Utils/LoopSimplify.cpp | 27 | ||||
| -rw-r--r-- | llvm/test/Transforms/LoopSimplify/ashr-crash.ll | 80 |
3 files changed, 104 insertions, 10 deletions
diff --git a/llvm/include/llvm/Analysis/ScalarEvolution.h b/llvm/include/llvm/Analysis/ScalarEvolution.h index a397046315b..26dd4dd5fcf 100644 --- a/llvm/include/llvm/Analysis/ScalarEvolution.h +++ b/llvm/include/llvm/Analysis/ScalarEvolution.h @@ -784,6 +784,13 @@ namespace llvm { /// disconnect it from a def-use chain linking it to a loop. void forgetValue(Value *V); + /// \brief Called when the client has changed the disposition of values in + /// this loop. + /// + /// We don't have a way to invalidate per-loop dispositions. Clear and + /// recompute is simpler. + void forgetLoopDispositions(const Loop *L) { LoopDispositions.clear(); } + /// GetMinTrailingZeros - Determine the minimum number of zero bits that S /// is guaranteed to end in (at every loop iteration). It is, at the same /// time, the minimum number of times S is divisible by 2. For example, diff --git a/llvm/lib/Transforms/Utils/LoopSimplify.cpp b/llvm/lib/Transforms/Utils/LoopSimplify.cpp index 6d5f16ca333..1927d288d43 100644 --- a/llvm/lib/Transforms/Utils/LoopSimplify.cpp +++ b/llvm/lib/Transforms/Utils/LoopSimplify.cpp @@ -309,6 +309,7 @@ ReprocessLoop: // Attempt to hoist out all instructions except for the // comparison and the branch. bool AllInvariant = true; + bool AnyInvariant = false; for (BasicBlock::iterator I = ExitingBlock->begin(); &*I != BI; ) { Instruction *Inst = I++; // Skip debug info intrinsics. @@ -316,12 +317,26 @@ ReprocessLoop: continue; if (Inst == CI) continue; - if (!L->makeLoopInvariant(Inst, Changed, - Preheader ? Preheader->getTerminator() : 0)) { + if (!L->makeLoopInvariant(Inst, AnyInvariant, + Preheader ? Preheader->getTerminator() : 0)) { AllInvariant = false; break; } } + if (AnyInvariant) { + Changed = true; + // If any reachable control flow within this loop has changed, notify + // ScalarEvolution. Currently assume the parent loop doesn't change + // (spliting edges doesn't count). If blocks, CFG edges, or other values + // in the parent loop change, then we need call to forgetLoop() for the + // parent instead. + if (SE) { + SE->forgetLoop(L); + // The loop disposition of all SCEV expressions that depend on any + // hoisted values have also changed. + SE->forgetLoopDispositions(L); + } + } if (!AllInvariant) continue; // The block has now been cleared of all instructions except for @@ -334,14 +349,6 @@ ReprocessLoop: DEBUG(dbgs() << "LoopSimplify: Eliminating exiting block " << ExitingBlock->getName() << "\n"); - // If any reachable control flow within this loop has changed, notify - // ScalarEvolution. Currently assume the parent loop doesn't change - // (spliting edges doesn't count). If blocks, CFG edges, or other values - // in the parent loop change, then we need call to forgetLoop() for the - // parent instead. - if (SE) - SE->forgetLoop(L); - assert(pred_begin(ExitingBlock) == pred_end(ExitingBlock)); Changed = true; LI->removeBlock(ExitingBlock); diff --git a/llvm/test/Transforms/LoopSimplify/ashr-crash.ll b/llvm/test/Transforms/LoopSimplify/ashr-crash.ll new file mode 100644 index 00000000000..f736eefc9b3 --- /dev/null +++ b/llvm/test/Transforms/LoopSimplify/ashr-crash.ll @@ -0,0 +1,80 @@ +; RUN: opt -basicaa -loop-rotate -licm -instcombine -indvars -loop-unroll -S %s | FileCheck %s +; +; PR18361: ScalarEvolution::getAddRecExpr(): +; Assertion `isLoopInvariant(Operands[i],... +; +; After a series of loop optimizations, SCEV's LoopDispositions grow stale. +; In particular, LoopSimplify hoists %cmp4, resulting in this SCEV for %add: +; {(zext i1 %cmp4 to i32),+,1}<nw><%for.cond1.preheader> +; +; When recomputing the SCEV for %ashr, we truncate the operands to get: +; (zext i1 %cmp4 to i16) +; +; This SCEV was never mapped to a value so never invalidated. It's +; loop disposition is still marked as non-loop-invariant, which is +; inconsistent with the AddRec. + +target datalayout = "e-i64:64-f80:128-n8:16:32:64-S128" +target triple = "x86_64-apple-macosx" + +@d = common global i32 0, align 4 +@a = common global i32 0, align 4 +@c = common global i32 0, align 4 +@b = common global i32 0, align 4 + +; Check that the def-use chain that leads to the bad SCEV is still +; there, and part of it is hoisted to the entry block. +; +; CHECK-LABEL: @foo +; CHECK-LABEL: entry: +; CHECK: %cmp4 +; CHECK-LABEL: for.cond1.preheader: +; CHECK-LABEL: for.body3: +; CHECK: %1 = zext i1 %cmp4 to i32 +; CHECK: %xor = xor i32 %1, 1 +define void @foo() { +entry: + br label %for.cond + +for.cond: ; preds = %for.inc7, %entry + %storemerge = phi i32 [ 0, %entry ], [ %inc8, %for.inc7 ] + %f.0 = phi i32 [ undef, %entry ], [ %f.1, %for.inc7 ] + store i32 %storemerge, i32* @d, align 4 + %cmp = icmp slt i32 %storemerge, 1 + br i1 %cmp, label %for.cond1, label %for.end9 + +for.cond1: ; preds = %for.cond, %for.body3 + %storemerge1 = phi i32 [ %inc, %for.body3 ], [ 0, %for.cond ] + %f.1 = phi i32 [ %xor, %for.body3 ], [ %f.0, %for.cond ] + store i32 %storemerge1, i32* @a, align 4 + %cmp2 = icmp slt i32 %storemerge1, 1 + br i1 %cmp2, label %for.body3, label %for.inc7 + +for.body3: ; preds = %for.cond1 + %0 = load i32* @c, align 4 + %cmp4 = icmp sge i32 %storemerge1, %0 + %conv = zext i1 %cmp4 to i32 + %1 = load i32* @d, align 4 + %add = add nsw i32 %conv, %1 + %sext = shl i32 %add, 16 + %conv6 = ashr exact i32 %sext, 16 + %xor = xor i32 %conv6, 1 + %inc = add nsw i32 %storemerge1, 1 + br label %for.cond1 + +for.inc7: ; preds = %for.cond1 + %2 = load i32* @d, align 4 + %inc8 = add nsw i32 %2, 1 + br label %for.cond + +for.end9: ; preds = %for.cond + %cmp10 = icmp sgt i32 %f.0, 0 + br i1 %cmp10, label %if.then, label %if.end + +if.then: ; preds = %for.end9 + store i32 0, i32* @b, align 4 + br label %if.end + +if.end: ; preds = %if.then, %for.end9 + ret void +} |
