[llvm] r315437 - [IRCE] Do not process empty safe ranges
Max Kazantsev via llvm-commits
llvm-commits at lists.llvm.org
Tue Oct 10 23:53:07 PDT 2017
Author: mkazantsev
Date: Tue Oct 10 23:53:07 2017
New Revision: 315437
URL: http://llvm.org/viewvc/llvm-project?rev=315437&view=rev
Log:
[IRCE] Do not process empty safe ranges
IRCE should not apply when the safe iteration range is proved to be empty.
In this case we do unneeded job creating pre/post loops and then never
go to the main loop.
This patch makes IRCE not apply to empty safe ranges, adds test for this
situation and also modifies one of existing tests where it used to happen
slightly.
Reviewed By: anna
Differential Revision: https://reviews.llvm.org/D38577
Modified:
llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
llvm/trunk/test/Transforms/IRCE/correct-loop-info.ll
llvm/trunk/test/Transforms/IRCE/single-access-no-preloop.ll
Modified: llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp?rev=315437&r1=315436&r2=315437&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp Tue Oct 10 23:53:07 2017
@@ -176,6 +176,7 @@ public:
Type *getType() const { return Begin->getType(); }
const SCEV *getBegin() const { return Begin; }
const SCEV *getEnd() const { return End; }
+ bool isEmpty() const { return Begin == End; }
};
/// This is the value the condition of the branch needs to evaluate to for the
@@ -1654,8 +1655,11 @@ static Optional<InductiveRangeCheck::Ran
IntersectRange(ScalarEvolution &SE,
const Optional<InductiveRangeCheck::Range> &R1,
const InductiveRangeCheck::Range &R2) {
- if (!R1.hasValue())
- return R2;
+ if (!R1.hasValue()) {
+ if (!R2.isEmpty())
+ return R2;
+ return None;
+ }
auto &R1Value = R1.getValue();
// TODO: we could widen the smaller range and have this work; but for now we
@@ -1666,7 +1670,11 @@ IntersectRange(ScalarEvolution &SE,
const SCEV *NewBegin = SE.getSMaxExpr(R1Value.getBegin(), R2.getBegin());
const SCEV *NewEnd = SE.getSMinExpr(R1Value.getEnd(), R2.getEnd());
- return InductiveRangeCheck::Range(NewBegin, NewEnd);
+ // If the resulting range is empty, just return None.
+ auto Ret = InductiveRangeCheck::Range(NewBegin, NewEnd);
+ if (Ret.isEmpty())
+ return None;
+ return Ret;
}
bool InductiveRangeCheckElimination::runOnLoop(Loop *L, LPPassManager &LPM) {
@@ -1735,6 +1743,8 @@ bool InductiveRangeCheckElimination::run
auto MaybeSafeIterRange =
IntersectRange(SE, SafeIterRange, Result.getValue());
if (MaybeSafeIterRange.hasValue()) {
+ assert(!MaybeSafeIterRange.getValue().isEmpty() &&
+ "We should never return empty ranges!");
RangeChecksToEliminate.push_back(IRC);
SafeIterRange = MaybeSafeIterRange.getValue();
}
Modified: llvm/trunk/test/Transforms/IRCE/correct-loop-info.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IRCE/correct-loop-info.ll?rev=315437&r1=315436&r2=315437&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IRCE/correct-loop-info.ll (original)
+++ llvm/trunk/test/Transforms/IRCE/correct-loop-info.ll Tue Oct 10 23:53:07 2017
@@ -21,7 +21,7 @@ define void @baz() personality i32* ()*
; CHECK: innerheader.preloop.preheader:
; CHECK-NEXT: br label [[INNERHEADER_PRELOOP:%.*]]
; CHECK: mainloop:
-; CHECK-NEXT: [[TMP0:%.*]] = icmp slt i32 [[INDVAR_END:%.*]], -1
+; CHECK-NEXT: [[TMP0:%.*]] = icmp slt i32 [[INDVAR_END:%.*]], 0
; CHECK-NEXT: br i1 [[TMP0]], label [[INNERHEADER_PREHEADER:%.*]], label [[MAIN_PSEUDO_EXIT:%.*]]
; CHECK: innerheader.preheader:
; CHECK-NEXT: br label [[INNERHEADER:%.*]]
@@ -31,11 +31,11 @@ define void @baz() personality i32* ()*
; CHECK-NEXT: to label [[BB5:%.*]] unwind label %outer_exiting.loopexit.split-lp.loopexit.split-lp
; CHECK: bb5:
; CHECK-NEXT: [[TMP6]] = add i32 [[TMP4]], 1
-; CHECK-NEXT: [[TMP7:%.*]] = icmp ult i32 [[TMP6]], 0
+; CHECK-NEXT: [[TMP7:%.*]] = icmp ult i32 [[TMP6]], 1
; CHECK-NEXT: br i1 true, label [[BB8]], label [[EXIT3_LOOPEXIT5:%.*]]
; CHECK: bb8:
; CHECK-NEXT: [[TMP9:%.*]] = icmp slt i32 [[TMP6]], 84
-; CHECK-NEXT: [[TMP1:%.*]] = icmp slt i32 [[TMP6]], -1
+; CHECK-NEXT: [[TMP1:%.*]] = icmp slt i32 [[TMP6]], 0
; CHECK-NEXT: br i1 [[TMP1]], label [[INNERHEADER]], label [[MAIN_EXIT_SELECTOR:%.*]]
; CHECK: main.exit.selector:
; CHECK-NEXT: [[TMP6_LCSSA:%.*]] = phi i32 [ [[TMP6]], [[BB8]] ]
@@ -90,7 +90,7 @@ define void @baz() personality i32* ()*
; CHECK-NEXT: to label [[BB5_PRELOOP:%.*]] unwind label [[OUTER_EXITING_LOOPEXIT:%.*]]
; CHECK: bb5.preloop:
; CHECK-NEXT: [[TMP6_PRELOOP]] = add i32 [[TMP4_PRELOOP]], 1
-; CHECK-NEXT: [[TMP7_PRELOOP:%.*]] = icmp ult i32 [[TMP6_PRELOOP]], 0
+; CHECK-NEXT: [[TMP7_PRELOOP:%.*]] = icmp ult i32 [[TMP6_PRELOOP]], 1
; CHECK-NEXT: br i1 [[TMP7_PRELOOP]], label [[BB8_PRELOOP]], label [[EXIT3_LOOPEXIT:%.*]]
; CHECK: bb8.preloop:
; CHECK-NEXT: [[TMP9_PRELOOP:%.*]] = icmp slt i32 [[TMP6_PRELOOP]], 84
@@ -112,7 +112,7 @@ define void @baz() personality i32* ()*
; CHECK-NEXT: to label [[BB5_POSTLOOP:%.*]] unwind label %outer_exiting.loopexit.split-lp.loopexit
; CHECK: bb5.postloop:
; CHECK-NEXT: [[TMP6_POSTLOOP]] = add i32 [[TMP4_POSTLOOP]], 1
-; CHECK-NEXT: [[TMP7_POSTLOOP:%.*]] = icmp ult i32 [[TMP6_POSTLOOP]], 0
+; CHECK-NEXT: [[TMP7_POSTLOOP:%.*]] = icmp ult i32 [[TMP6_POSTLOOP]], 1
; CHECK-NEXT: br i1 [[TMP7_POSTLOOP]], label [[BB8_POSTLOOP]], label [[EXIT3_LOOPEXIT4:%.*]]
; CHECK: bb8.postloop:
; CHECK-NEXT: [[TMP9_POSTLOOP:%.*]] = icmp slt i32 [[TMP6_POSTLOOP]], 84
@@ -135,7 +135,7 @@ innerheader:
bb5: ; preds = %innerheader
%tmp6 = add i32 %tmp4, 1
- %tmp7 = icmp ult i32 %tmp6, 0
+ %tmp7 = icmp ult i32 %tmp6, 1
br i1 %tmp7, label %bb8, label %exit3
bb8: ; preds = %bb5
Modified: llvm/trunk/test/Transforms/IRCE/single-access-no-preloop.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IRCE/single-access-no-preloop.ll?rev=315437&r1=315436&r2=315437&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IRCE/single-access-no-preloop.ll (original)
+++ llvm/trunk/test/Transforms/IRCE/single-access-no-preloop.ll Tue Oct 10 23:53:07 2017
@@ -113,5 +113,71 @@ define void @single_access_no_preloop_wi
; CHECK: %next.postloop = icmp slt i32 %idx.next.postloop, %n
; CHECK: br i1 %next.postloop, label %loop.postloop, label %exit.loopexit
+; Make sure that we do not do IRCE if we know that the safe iteration range of
+; the main loop is empty.
+
+define void @single_access_empty_range(i32 *%arr, i32 *%a_len_ptr, i32 %n) {
+ entry:
+ %len = load i32, i32* %a_len_ptr, !range !0
+ %first.itr.check = icmp sgt i32 %n, 0
+ br i1 %first.itr.check, label %loop, label %exit
+
+ loop:
+ %idx = phi i32 [ 0, %entry ] , [ %idx.next, %in.bounds ]
+ %idx.next = add i32 %idx, 1
+ %abc = icmp slt i32 %idx, 0
+ br i1 %abc, label %in.bounds, label %out.of.bounds, !prof !1
+
+ in.bounds:
+ %addr = getelementptr i32, i32* %arr, i32 %idx
+ store i32 0, i32* %addr
+ %next = icmp slt i32 %idx.next, %n
+ br i1 %next, label %loop, label %exit
+
+ out.of.bounds:
+ ret void
+
+ exit:
+ ret void
+}
+
+; CHECK-LABEL: @single_access_empty_range(
+; CHECK-NOT: br i1 false
+; CHECK-NOT: preloop
+; CHECK-NOT: postloop
+
+define void @single_access_empty_range_2(i32 *%arr, i32 *%a_len_ptr, i32 %n) {
+ entry:
+ %len = load i32, i32* %a_len_ptr, !range !0
+ %first.itr.check = icmp sgt i32 %n, 0
+ br i1 %first.itr.check, label %loop, label %exit
+
+ loop:
+ %idx = phi i32 [ 0, %entry ] , [ %idx.next, %in.bounds2 ]
+ %idx.next = add i32 %idx, 1
+ %abc = icmp slt i32 %idx, 60
+ br i1 %abc, label %in.bounds1, label %out.of.bounds, !prof !1
+
+ in.bounds1:
+ %def = icmp slt i32 %idx, 0
+ br i1 %def, label %in.bounds2, label %out.of.bounds, !prof !1
+
+in.bounds2:
+ %addr = getelementptr i32, i32* %arr, i32 %idx
+ store i32 0, i32* %addr
+ %next = icmp slt i32 %idx.next, %n
+ br i1 %next, label %loop, label %exit
+
+ out.of.bounds:
+ ret void
+
+ exit:
+ ret void
+}
+
+; CHECK-LABEL: @single_access_empty_range_2(
+; CHECK-NOT: br i1 false
+; CHECK-NOT: preloop
+
!0 = !{i32 0, i32 2147483647}
!1 = !{!"branch_weights", i32 64, i32 4}
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