[llvm] r254977 - [IndVars] Have getInsertPointForUses preserve LCSSA
Sanjoy Das via llvm-commits
llvm-commits at lists.llvm.org
Mon Dec 7 16:13:22 PST 2015
Author: sanjoy
Date: Mon Dec 7 18:13:21 2015
New Revision: 254977
URL: http://llvm.org/viewvc/llvm-project?rev=254977&view=rev
Log:
[IndVars] Have getInsertPointForUses preserve LCSSA
Summary:
Also add a stricter post-condition for IndVarSimplify.
Fixes PR25578. Test case by Michael Zolotukhin.
Reviewers: hfinkel, atrick, mzolotukhin
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D15059
Added:
llvm/trunk/test/Transforms/IndVarSimplify/pr25578.ll
Modified:
llvm/trunk/include/llvm/Analysis/LoopInfo.h
llvm/trunk/lib/Analysis/LoopInfo.cpp
llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
Modified: llvm/trunk/include/llvm/Analysis/LoopInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/LoopInfo.h?rev=254977&r1=254976&r2=254977&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/LoopInfo.h (original)
+++ llvm/trunk/include/llvm/Analysis/LoopInfo.h Mon Dec 7 18:13:21 2015
@@ -402,6 +402,9 @@ public:
/// isLCSSAForm - Return true if the Loop is in LCSSA form
bool isLCSSAForm(DominatorTree &DT) const;
+ /// \brief Return true if this Loop and all inner subloops are in LCSSA form.
+ bool isRecursivelyLCSSAForm(DominatorTree &DT) const;
+
/// isLoopSimplifyForm - Return true if the Loop is in the form that
/// the LoopSimplify form transforms loops to, which is sometimes called
/// normal form.
Modified: llvm/trunk/lib/Analysis/LoopInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/LoopInfo.cpp?rev=254977&r1=254976&r2=254977&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/LoopInfo.cpp (original)
+++ llvm/trunk/lib/Analysis/LoopInfo.cpp Mon Dec 7 18:13:21 2015
@@ -200,6 +200,15 @@ bool Loop::isLCSSAForm(DominatorTree &DT
return true;
}
+bool Loop::isRecursivelyLCSSAForm(DominatorTree &DT) const {
+ if (!isLCSSAForm(DT))
+ return false;
+
+ return std::all_of(begin(), end(), [&](const Loop *L) {
+ return L->isRecursivelyLCSSAForm(DT);
+ });
+}
+
/// isLoopSimplifyForm - Return true if the Loop is in the form that
/// the LoopSimplify form transforms loops to, which is sometimes called
/// normal form.
Modified: llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp?rev=254977&r1=254976&r2=254977&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp Mon Dec 7 18:13:21 2015
@@ -50,6 +50,7 @@
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Utils/LoopUtils.h"
#include "llvm/Transforms/Utils/SimplifyIndVar.h"
using namespace llvm;
@@ -215,7 +216,7 @@ bool IndVarSimplify::isValidRewrite(Valu
/// loop. For PHI nodes, there may be multiple uses, so compute the nearest
/// common dominator for the incoming blocks.
static Instruction *getInsertPointForUses(Instruction *User, Value *Def,
- DominatorTree *DT) {
+ DominatorTree *DT, LoopInfo *LI) {
PHINode *PHI = dyn_cast<PHINode>(User);
if (!PHI)
return User;
@@ -234,10 +235,21 @@ static Instruction *getInsertPointForUse
InsertPt = InsertBB->getTerminator();
}
assert(InsertPt && "Missing phi operand");
- assert((!isa<Instruction>(Def) ||
- DT->dominates(cast<Instruction>(Def), InsertPt)) &&
- "def does not dominate all uses");
- return InsertPt;
+
+ auto *DefI = dyn_cast<Instruction>(Def);
+ if (!DefI)
+ return InsertPt;
+
+ assert(DT->dominates(DefI, InsertPt) && "def does not dominate all uses");
+
+ auto *L = LI->getLoopFor(DefI->getParent());
+ assert(!L || L->contains(LI->getLoopFor(InsertPt->getParent())));
+
+ for (auto *DTN = (*DT)[InsertPt->getParent()]; DTN; DTN = DTN->getIDom())
+ if (LI->getLoopFor(DTN->getBlock()) == L)
+ return DTN->getBlock()->getTerminator();
+
+ llvm_unreachable("DefI dominates InsertPt!");
}
//===----------------------------------------------------------------------===//
@@ -528,8 +540,8 @@ Value *IndVarSimplify::expandSCEVIfNeede
/// able to brute-force evaluate arbitrary instructions as long as they have
/// constant operands at the beginning of the loop.
void IndVarSimplify::rewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter) {
- // Verify the input to the pass in already in LCSSA form.
- assert(L->isLCSSAForm(*DT));
+ // Check a pre-condition.
+ assert(L->isRecursivelyLCSSAForm(*DT) && "Indvars did not preserve LCSSA!");
SmallVector<BasicBlock*, 8> ExitBlocks;
L->getUniqueExitBlocks(ExitBlocks);
@@ -1167,10 +1179,11 @@ const SCEVAddRecExpr *WidenIV::getWideRe
/// This IV user cannot be widen. Replace this use of the original narrow IV
/// with a truncation of the new wide IV to isolate and eliminate the narrow IV.
-static void truncateIVUse(NarrowIVDefUse DU, DominatorTree *DT) {
+static void truncateIVUse(NarrowIVDefUse DU, DominatorTree *DT, LoopInfo *LI) {
DEBUG(dbgs() << "INDVARS: Truncate IV " << *DU.WideDef
<< " for user " << *DU.NarrowUse << "\n");
- IRBuilder<> Builder(getInsertPointForUses(DU.NarrowUse, DU.NarrowDef, DT));
+ IRBuilder<> Builder(
+ getInsertPointForUses(DU.NarrowUse, DU.NarrowDef, DT, LI));
Value *Trunc = Builder.CreateTrunc(DU.WideDef, DU.NarrowDef->getType());
DU.NarrowUse->replaceUsesOfWith(DU.NarrowDef, Trunc);
}
@@ -1207,7 +1220,8 @@ bool WidenIV::widenLoopCompare(NarrowIVD
assert (CastWidth <= IVWidth && "Unexpected width while widening compare.");
// Widen the compare instruction.
- IRBuilder<> Builder(getInsertPointForUses(DU.NarrowUse, DU.NarrowDef, DT));
+ IRBuilder<> Builder(
+ getInsertPointForUses(DU.NarrowUse, DU.NarrowDef, DT, LI));
DU.NarrowUse->replaceUsesOfWith(DU.NarrowDef, DU.WideDef);
// Widen the other operand of the compare, if necessary.
@@ -1229,7 +1243,7 @@ Instruction *WidenIV::widenIVUse(NarrowI
// After SimplifyCFG most loop exit targets have a single predecessor.
// Otherwise fall back to a truncate within the loop.
if (UsePhi->getNumOperands() != 1)
- truncateIVUse(DU, DT);
+ truncateIVUse(DU, DT, LI);
else {
PHINode *WidePhi =
PHINode::Create(DU.WideDef->getType(), 1, UsePhi->getName() + ".wide",
@@ -1297,7 +1311,7 @@ Instruction *WidenIV::widenIVUse(NarrowI
// This user does not evaluate to a recurence after widening, so don't
// follow it. Instead insert a Trunc to kill off the original use,
// eventually isolating the original narrow IV so it can be removed.
- truncateIVUse(DU, DT);
+ truncateIVUse(DU, DT, LI);
return nullptr;
}
// Assume block terminators cannot evaluate to a recurrence. We can't to
@@ -2165,9 +2179,9 @@ bool IndVarSimplify::runOnLoop(Loop *L,
// Clean up dead instructions.
Changed |= DeleteDeadPHIs(L->getHeader(), TLI);
+
// Check a post-condition.
- assert(L->isLCSSAForm(*DT) &&
- "Indvars did not leave the loop in lcssa form!");
+ assert(L->isRecursivelyLCSSAForm(*DT) && "Indvars did not preserve LCSSA!");
// Verify that LFTR, and any other change have not interfered with SCEV's
// ability to compute trip count.
Added: llvm/trunk/test/Transforms/IndVarSimplify/pr25578.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/pr25578.ll?rev=254977&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/pr25578.ll (added)
+++ llvm/trunk/test/Transforms/IndVarSimplify/pr25578.ll Mon Dec 7 18:13:21 2015
@@ -0,0 +1,45 @@
+; RUN: opt < %s -indvars -S | FileCheck %s
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+; CHECK-LABEL: @foo
+define void @foo() {
+entry:
+ br label %L1_header
+
+L1_header:
+ br label %L2_header
+
+; CHECK: L2_header:
+; CHECK: %[[INDVAR:.*]] = phi i64
+; CHECK: %[[TRUNC:.*]] = trunc i64 %[[INDVAR]] to i32
+L2_header:
+ %i = phi i32 [ 0, %L1_header ], [ %i_next, %L2_latch ]
+ %i_prom = sext i32 %i to i64
+ br label %L3_header
+
+L3_header:
+ br i1 undef, label %L3_latch, label %L2_exiting_1
+
+L3_latch:
+ br i1 undef, label %L3_header, label %L2_exiting_2
+
+L2_exiting_1:
+ br i1 undef, label %L2_latch, label %L1_latch
+
+L2_exiting_2:
+ br i1 undef, label %L2_latch, label %L1_latch
+
+L2_latch:
+ %i_next = add nsw i32 %i, 1
+ br label %L2_header
+
+L1_latch:
+; CHECK: L1_latch:
+; CHECK: %i_lcssa = phi i32 [ %[[TRUNC]], %L2_exiting_1 ], [ %[[TRUNC]], %L2_exiting_2 ]
+
+ %i_lcssa = phi i32 [ %i, %L2_exiting_1 ], [ %i, %L2_exiting_2 ]
+ br i1 undef, label %exit, label %L1_header
+
+exit:
+ ret void
+}
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