[llvm] r346397 - Return "[IndVars] Smart hard uses detection"
Max Kazantsev via llvm-commits
llvm-commits at lists.llvm.org
Thu Nov 8 03:54:35 PST 2018
Author: mkazantsev
Date: Thu Nov 8 03:54:35 2018
New Revision: 346397
URL: http://llvm.org/viewvc/llvm-project?rev=346397&view=rev
Log:
Return "[IndVars] Smart hard uses detection"
The patch has been reverted because it ended up prohibiting propagation
of a constant to exit value. For such values, we should skip all checks
related to hard uses because propagating a constant is always profitable.
Differential Revision: https://reviews.llvm.org/D53691
Modified:
llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
llvm/trunk/test/Analysis/ScalarEvolution/pr28705.ll
llvm/trunk/test/Transforms/IndVarSimplify/dont-recompute.ll
llvm/trunk/test/Transforms/IndVarSimplify/lrev-existing-umin.ll
Modified: llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp?rev=346397&r1=346396&r2=346397&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp Thu Nov 8 03:54:35 2018
@@ -145,6 +145,7 @@ class IndVarSimplify {
bool canLoopBeDeleted(Loop *L, SmallVector<RewritePhi, 8> &RewritePhiSet);
bool rewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter);
bool rewriteFirstIterationLoopExitValues(Loop *L);
+ bool hasHardUserWithinLoop(const Loop *L, const Instruction *I) const;
bool linearFunctionTestReplace(Loop *L, const SCEV *BackedgeTakenCount,
PHINode *IndVar, SCEVExpander &Rewriter);
@@ -524,6 +525,29 @@ struct RewritePhi {
// As a side effect, reduces the amount of IV processing within the loop.
//===----------------------------------------------------------------------===//
+bool IndVarSimplify::hasHardUserWithinLoop(const Loop *L, const Instruction *I) const {
+ SmallPtrSet<const Instruction *, 8> Visited;
+ SmallVector<const Instruction *, 8> WorkList;
+ Visited.insert(I);
+ WorkList.push_back(I);
+ while (!WorkList.empty()) {
+ const Instruction *Curr = WorkList.pop_back_val();
+ // This use is outside the loop, nothing to do.
+ if (!L->contains(Curr))
+ continue;
+ // Do we assume it is a "hard" use which will not be eliminated easily?
+ if (Curr->mayHaveSideEffects())
+ return true;
+ // Otherwise, add all its users to worklist.
+ for (auto U : Curr->users()) {
+ auto *UI = cast<Instruction>(U);
+ if (Visited.insert(UI).second)
+ WorkList.push_back(UI);
+ }
+ }
+ return false;
+}
+
/// Check to see if this loop has a computable loop-invariant execution count.
/// If so, this means that we can compute the final value of any expressions
/// that are recurrent in the loop, and substitute the exit values from the loop
@@ -598,19 +622,8 @@ bool IndVarSimplify::rewriteLoopExitValu
// Computing the value outside of the loop brings no benefit if it is
// definitely used inside the loop in a way which can not be optimized
// away.
- if (ExitValue->getSCEVType()>=scMulExpr) {
- bool HasHardInternalUses = false;
- for (auto *IB : Inst->users()) {
- Instruction *UseInstr = cast<Instruction>(IB);
- unsigned Opc = UseInstr->getOpcode();
- if (L->contains(UseInstr) && Opc == Instruction::Call) {
- HasHardInternalUses = true;
- break;
- }
- }
- if (HasHardInternalUses)
- continue;
- }
+ if (!isa<SCEVConstant>(ExitValue) && hasHardUserWithinLoop(L, Inst))
+ continue;
bool HighCost = Rewriter.isHighCostExpansion(ExitValue, L, Inst);
Value *ExitVal = Rewriter.expandCodeFor(ExitValue, PN->getType(), Inst);
Modified: llvm/trunk/test/Analysis/ScalarEvolution/pr28705.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/ScalarEvolution/pr28705.ll?rev=346397&r1=346396&r2=346397&view=diff
==============================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/pr28705.ll (original)
+++ llvm/trunk/test/Analysis/ScalarEvolution/pr28705.ll Thu Nov 8 03:54:35 2018
@@ -1,11 +1,11 @@
; PR28705
; RUN: opt < %s -indvars -S | FileCheck %s
-; Check IndVarSimplify replaces the exitval use of the induction var "%inc.i.i"
-; with "%.sroa.speculated + 1".
+; Check IndVarSimplify doesn't replace external use of the induction var
+; "%inc.i.i" with "%.sroa.speculated + 1" because it is not profitable.
;
; CHECK-LABEL: @foo(
-; CHECK: %[[EXIT:.+]] = sub i32 %.sroa.speculated, -1
+; CHECK: %[[EXIT:.+]] = phi i32 [ %inc.i.i, %for.body650 ]
; CHECK: %DB.sroa.9.0.lcssa = phi i32 [ 1, %entry ], [ %[[EXIT]], %loopexit ]
;
define void @foo(i32 %sub.ptr.div.i, i8* %ref.i1174) local_unnamed_addr {
Modified: llvm/trunk/test/Transforms/IndVarSimplify/dont-recompute.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/dont-recompute.ll?rev=346397&r1=346396&r2=346397&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/dont-recompute.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/dont-recompute.ll Thu Nov 8 03:54:35 2018
@@ -123,3 +123,54 @@ for.end:
tail call void @func(i32 %soft_use)
ret void
}
+
+; CHECK-LABEL: @test5(
+define void @test5(i32 %m) nounwind uwtable {
+entry:
+ br label %for.body
+
+for.body: ; preds = %for.body, %entry
+ %i.06 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+ %a.05 = phi i32 [ 0, %entry ], [ %add, %for.body ]
+ %add = add i32 %a.05, %m
+ %soft_use = add i32 %add, 123
+; CHECK: tail call void @func(i32 %soft_use)
+ tail call void @func(i32 %soft_use)
+ %inc = add nsw i32 %i.06, 1
+ %exitcond = icmp eq i32 %inc, 186
+ br i1 %exitcond, label %for.end, label %for.body
+
+for.end: ; preds = %for.body
+; CHECK: for.end:
+; CHECK-NOT: mul i32 %m, 186
+; CHECK:%add.lcssa = phi i32 [ %add, %for.body ]
+; CHECK-NEXT: tail call void @func(i32 %add.lcssa)
+ tail call void @func(i32 %add)
+ ret void
+}
+
+; CHECK-LABEL: @test6(
+define void @test6(i32 %m, i32* %p) nounwind uwtable {
+entry:
+ br label %for.body
+
+for.body: ; preds = %for.body, %entry
+ %i.06 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+ %a.05 = phi i32 [ 0, %entry ], [ %add, %for.body ]
+ %add = add i32 %a.05, %m
+ %soft_use = add i32 %add, 123
+; CHECK: store i32 %soft_use, i32* %pidx
+ %pidx = getelementptr i32, i32* %p, i32 %add
+ store i32 %soft_use, i32* %pidx
+ %inc = add nsw i32 %i.06, 1
+ %exitcond = icmp eq i32 %inc, 186
+ br i1 %exitcond, label %for.end, label %for.body
+
+for.end: ; preds = %for.body
+; CHECK: for.end:
+; CHECK-NOT: mul i32 %m, 186
+; CHECK:%add.lcssa = phi i32 [ %add, %for.body ]
+; CHECK-NEXT: tail call void @func(i32 %add.lcssa)
+ tail call void @func(i32 %add)
+ ret void
+}
Modified: llvm/trunk/test/Transforms/IndVarSimplify/lrev-existing-umin.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/lrev-existing-umin.ll?rev=346397&r1=346396&r2=346397&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/lrev-existing-umin.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/lrev-existing-umin.ll Thu Nov 8 03:54:35 2018
@@ -1,5 +1,7 @@
; RUN: opt -S -indvars < %s | FileCheck %s
+; Do not rewrite the user outside the loop because we must keep the instruction
+; inside the loop due to store. Rewrite doesn't give us any profit.
define void @f(i32 %length.i.88, i32 %length.i, i8* %tmp12, i32 %tmp10, i8* %tmp8) {
; CHECK-LABEL: @f(
not_zero11.preheader:
@@ -21,6 +23,42 @@ not_zero11:
%tmp22 = add nuw nsw i32 %v_1, 1
%tmp23 = icmp slt i32 %tmp22, %tmp14
br i1 %tmp23, label %not_zero11, label %main.exit.selector
+
+main.exit.selector:
+; CHECK-LABEL: main.exit.selector:
+; CHECK: %tmp22.lcssa = phi i32 [ %tmp22, %not_zero11 ]
+; CHECK: %tmp24 = icmp slt i32 %tmp22.lcssa, %length.
+ %tmp24 = icmp slt i32 %tmp22, %length.i
+ br i1 %tmp24, label %not_zero11.postloop, label %leave
+
+leave:
+ ret void
+
+not_zero11.postloop:
+ ret void
+}
+
+; Rewrite the user outside the loop because there is no hard users inside the loop.
+define void @f1(i32 %length.i.88, i32 %length.i, i8* %tmp12, i32 %tmp10, i8* %tmp8) {
+; CHECK-LABEL: @f1(
+not_zero11.preheader:
+ %tmp13 = icmp ugt i32 %length.i, %length.i.88
+ %tmp14 = select i1 %tmp13, i32 %length.i.88, i32 %length.i
+ %tmp15 = icmp sgt i32 %tmp14, 0
+ br i1 %tmp15, label %not_zero11, label %not_zero11.postloop
+
+not_zero11:
+ %v_1 = phi i32 [ %tmp22, %not_zero11 ], [ 0, %not_zero11.preheader ]
+ %tmp16 = zext i32 %v_1 to i64
+ %tmp17 = getelementptr inbounds i8, i8* %tmp8, i64 %tmp16
+ %tmp18 = load i8, i8* %tmp17, align 1
+ %tmp19 = zext i8 %tmp18 to i32
+ %tmp20 = or i32 %tmp19, %tmp10
+ %tmp21 = trunc i32 %tmp20 to i8
+ %addr22 = getelementptr inbounds i8, i8* %tmp12, i64 %tmp16
+ %tmp22 = add nuw nsw i32 %v_1, 1
+ %tmp23 = icmp slt i32 %tmp22, %tmp14
+ br i1 %tmp23, label %not_zero11, label %main.exit.selector
main.exit.selector:
; CHECK-LABEL: main.exit.selector:
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