[llvm-commits] [llvm] r101008 - in /llvm/trunk: lib/Transforms/Scalar/IndVarSimplify.cpp test/Transforms/IndVarSimplify/eliminate-comparison.ll
Dan Gohman
gohman at apple.com
Sun Apr 11 19:21:50 PDT 2010
Author: djg
Date: Sun Apr 11 21:21:50 2010
New Revision: 101008
URL: http://llvm.org/viewvc/llvm-project?rev=101008&view=rev
Log:
Re-apply r101000, with a fix: Don't eliminate an icmp which is part of
the loop exit test. This usually doesn't come up for a variety of
reasons, but it isn't impossible, so make IndVarSimplify handle it
conservatively.
Added:
llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll
- copied, changed from r101000, llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp?rev=101008&r1=101007&r2=101008&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp Sun Apr 11 21:21:50 2010
@@ -97,6 +97,7 @@
private:
+ void EliminateIVComparisons();
void RewriteNonIntegerIVs(Loop *L);
ICmpInst *LinearFunctionTestReplace(Loop *L, const SCEV *BackedgeTakenCount,
@@ -336,6 +337,40 @@
SE->forgetLoop(L);
}
+void IndVarSimplify::EliminateIVComparisons() {
+ // Look for ICmp users.
+ for (IVUsers::iterator I = IU->begin(), E = IU->end(); I != E;) {
+ IVStrideUse &UI = *I++;
+ ICmpInst *ICmp = dyn_cast<ICmpInst>(UI.getUser());
+ if (!ICmp) continue;
+
+ bool Swapped = UI.getOperandValToReplace() == ICmp->getOperand(1);
+ ICmpInst::Predicate Pred = ICmp->getPredicate();
+ if (Swapped) Pred = ICmpInst::getSwappedPredicate(Pred);
+
+ // Get the SCEVs for the ICmp operands.
+ const SCEV *S = IU->getReplacementExpr(UI);
+ const SCEV *X = SE->getSCEV(ICmp->getOperand(!Swapped));
+
+ // Simplify unnecessary loops away.
+ const Loop *ICmpLoop = LI->getLoopFor(ICmp->getParent());
+ S = SE->getSCEVAtScope(S, ICmpLoop);
+ X = SE->getSCEVAtScope(X, ICmpLoop);
+
+ // If the condition is always true or always false, replace it with
+ // a constant value.
+ if (SE->isKnownPredicate(Pred, S, X))
+ ICmp->replaceAllUsesWith(ConstantInt::getTrue(ICmp->getContext()));
+ else if (SE->isKnownPredicate(ICmpInst::getInversePredicate(Pred), S, X))
+ ICmp->replaceAllUsesWith(ConstantInt::getFalse(ICmp->getContext()));
+ else
+ continue;
+
+ DEBUG(dbgs() << "INDVARS: Eliminated comparison: " << *ICmp << '\n');
+ ICmp->eraseFromParent();
+ }
+}
+
bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
IU = &getAnalysis<IVUsers>();
LI = &getAnalysis<LoopInfo>();
@@ -427,10 +462,19 @@
ExitingBlock) {
assert(NeedCannIV &&
"LinearFunctionTestReplace requires a canonical induction variable");
+
// Can't rewrite non-branch yet.
- if (BranchInst *BI = dyn_cast<BranchInst>(ExitingBlock->getTerminator()))
+ if (BranchInst *BI = dyn_cast<BranchInst>(ExitingBlock->getTerminator())) {
+ // Eliminate comparisons which are always true or always false, due to
+ // the known backedge-taken count. This may include comparisons which
+ // are currently controlling (part of) the loop exit, so we can only do
+ // it when we know we're going to insert our own loop exit code.
+ EliminateIVComparisons();
+
+ // Insert new loop exit code.
NewICmp = LinearFunctionTestReplace(L, BackedgeTakenCount, IndVar,
ExitingBlock, BI, Rewriter);
+ }
}
// Rewrite IV-derived expressions. Clears the rewriter cache.
Copied: llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll (from r101000, llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll)
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll?p2=llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll&p1=llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll&r1=101000&r2=101008&rev=101008&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll Sun Apr 11 21:21:50 2010
@@ -1,14 +1,15 @@
; RUN: opt -indvars -S < %s | FileCheck %s
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+
+ at X = external global [0 x double]
+
; Indvars should be able to simplify simple comparisons involving
; induction variables.
+; CHECK: @foo
; CHECK: %cond = and i1 %tobool.not, true
-target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
-
- at X = external global [0 x double]
-
define void @foo(i64 %n, i32* nocapture %p) nounwind {
entry:
%cmp9 = icmp sgt i64 %n, 0
@@ -38,3 +39,46 @@
return:
ret void
}
+
+; Don't eliminate an icmp that's contributing to the loop exit test though.
+
+; CHECK: @_ZNK4llvm5APInt3ultERKS0_
+; CHECK: %tmp99 = icmp sgt i32 %i, -1
+
+define i32 @_ZNK4llvm5APInt3ultERKS0_(i32 %tmp2.i1, i64** %tmp65, i64** %tmp73, i64** %tmp82, i64** %tmp90) {
+entry:
+ br label %bb18
+
+bb13:
+ %tmp66 = load i64** %tmp65, align 4
+ %tmp68 = getelementptr inbounds i64* %tmp66, i32 %i
+ %tmp69 = load i64* %tmp68, align 4
+ %tmp74 = load i64** %tmp73, align 4
+ %tmp76 = getelementptr inbounds i64* %tmp74, i32 %i
+ %tmp77 = load i64* %tmp76, align 4
+ %tmp78 = icmp ugt i64 %tmp69, %tmp77
+ br i1 %tmp78, label %bb20.loopexit, label %bb15
+
+bb15:
+ %tmp83 = load i64** %tmp82, align 4
+ %tmp85 = getelementptr inbounds i64* %tmp83, i32 %i
+ %tmp86 = load i64* %tmp85, align 4
+ %tmp91 = load i64** %tmp90, align 4
+ %tmp93 = getelementptr inbounds i64* %tmp91, i32 %i
+ %tmp94 = load i64* %tmp93, align 4
+ %tmp95 = icmp ult i64 %tmp86, %tmp94
+ br i1 %tmp95, label %bb20.loopexit, label %bb17
+
+bb17:
+ %tmp97 = add nsw i32 %i, -1
+ br label %bb18
+
+bb18:
+ %i = phi i32 [ %tmp2.i1, %entry ], [ %tmp97, %bb17 ]
+ %tmp99 = icmp sgt i32 %i, -1
+ br i1 %tmp99, label %bb13, label %bb20.loopexit
+
+bb20.loopexit:
+ %tmp.0.ph = phi i32 [ 0, %bb18 ], [ 1, %bb15 ], [ 0, %bb13 ]
+ ret i32 %tmp.0.ph
+}
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