[llvm] r328933 - [LoopRotate] Rotate loops with loop exiting latches
David Green via llvm-commits
llvm-commits at lists.llvm.org
Sun Apr 1 05:48:24 PDT 2018
Author: dmgreen
Date: Sun Apr 1 05:48:24 2018
New Revision: 328933
URL: http://llvm.org/viewvc/llvm-project?rev=328933&view=rev
Log:
[LoopRotate] Rotate loops with loop exiting latches
If a loop has a loop exiting latch, it can be profitable
to rotate the loop if it leads to the simplification of
a phi node. Perform rotation in these cases even if loop
rotate itself didnt simplify the loop to get there.
Differential Revision: https://reviews.llvm.org/D44199
Added:
llvm/trunk/test/Transforms/LoopRotate/loopexitinglatch.ll
Modified:
llvm/trunk/lib/Transforms/Utils/LoopRotationUtils.cpp
Modified: llvm/trunk/lib/Transforms/Utils/LoopRotationUtils.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopRotationUtils.cpp?rev=328933&r1=328932&r2=328933&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopRotationUtils.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LoopRotationUtils.cpp Sun Apr 1 05:48:24 2018
@@ -163,6 +163,27 @@ static void RewriteUsesOfClonedInstructi
}
}
+// Look for a phi which is only used outside the loop (via a LCSSA phi)
+// in the exit from the header. This means that rotating the loop can
+// remove the phi.
+static bool shouldRotateLoopExitingLatch(Loop *L) {
+ BasicBlock *Header = L->getHeader();
+ BasicBlock *HeaderExit = Header->getTerminator()->getSuccessor(0);
+ if (L->contains(HeaderExit))
+ HeaderExit = Header->getTerminator()->getSuccessor(1);
+
+ for (auto &Phi : Header->phis()) {
+ // Look for uses of this phi in the loop/via exits other than the header.
+ if (llvm::any_of(Phi.users(), [HeaderExit](const User *U) {
+ return cast<Instruction>(U)->getParent() != HeaderExit;
+ }))
+ continue;
+ return true;
+ }
+
+ return false;
+}
+
/// Rotate loop LP. Return true if the loop is rotated.
///
/// \param SimplifiedLatch is true if the latch was just folded into the final
@@ -197,8 +218,9 @@ bool LoopRotate::rotateLoop(Loop *L, boo
return false;
// Rotate if either the loop latch does *not* exit the loop, or if the loop
- // latch was just simplified.
- if (L->isLoopExiting(OrigLatch) && !SimplifiedLatch)
+ // latch was just simplified. Or if we think it will be profitable.
+ if (L->isLoopExiting(OrigLatch) && !SimplifiedLatch &&
+ !shouldRotateLoopExitingLatch(L))
return false;
// Check size of original header and reject loop if it is very big or we can't
Added: llvm/trunk/test/Transforms/LoopRotate/loopexitinglatch.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopRotate/loopexitinglatch.ll?rev=328933&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopRotate/loopexitinglatch.ll (added)
+++ llvm/trunk/test/Transforms/LoopRotate/loopexitinglatch.ll Sun Apr 1 05:48:24 2018
@@ -0,0 +1,234 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -loop-rotate < %s -verify-loop-info -verify-dom-info | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "thumbv8m.base-arm-none-eabi"
+
+%struct.List = type { %struct.List*, i32 }
+
+define void @list_add(%struct.List** nocapture %list, %struct.List* %data) {
+; CHECK-LABEL: @list_add(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = load %struct.List*, %struct.List** [[LIST:%.*]], align 4
+; CHECK-NEXT: [[VAL2:%.*]] = getelementptr inbounds [[STRUCT_LIST:%.*]], %struct.List* [[TMP0]], i32 0, i32 1
+; CHECK-NEXT: [[TMP1:%.*]] = load i32, i32* [[VAL2]], align 4
+; CHECK-NEXT: [[VAL1:%.*]] = getelementptr inbounds [[STRUCT_LIST]], %struct.List* [[DATA:%.*]], i32 0, i32 1
+; CHECK-NEXT: [[TMP2:%.*]] = load i32, i32* [[VAL1]], align 4
+; CHECK-NEXT: [[CMP3:%.*]] = icmp slt i32 [[TMP1]], [[TMP2]]
+; CHECK-NEXT: br i1 [[CMP3]], label [[IF_THEN_LR_PH:%.*]], label [[IF_ELSE6:%.*]]
+; CHECK: if.then.lr.ph:
+; CHECK-NEXT: br label [[IF_THEN:%.*]]
+; CHECK: for.cond:
+; CHECK-NEXT: [[CURR_0:%.*]] = phi %struct.List* [ [[TMP5:%.*]], [[IF_THEN]] ]
+; CHECK-NEXT: [[PREV_0:%.*]] = phi %struct.List* [ [[CURR_04:%.*]], [[IF_THEN]] ]
+; CHECK-NEXT: [[VAL:%.*]] = getelementptr inbounds [[STRUCT_LIST]], %struct.List* [[CURR_0]], i32 0, i32 1
+; CHECK-NEXT: [[TMP3:%.*]] = load i32, i32* [[VAL]], align 4
+; CHECK-NEXT: [[TMP4:%.*]] = load i32, i32* [[VAL1]], align 4
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[TMP3]], [[TMP4]]
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN]], label [[FOR_COND_IF_ELSE6_CRIT_EDGE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: [[CURR_04]] = phi %struct.List* [ [[TMP0]], [[IF_THEN_LR_PH]] ], [ [[CURR_0]], [[FOR_COND:%.*]] ]
+; CHECK-NEXT: [[NEXT:%.*]] = getelementptr inbounds [[STRUCT_LIST]], %struct.List* [[CURR_04]], i32 0, i32 0
+; CHECK-NEXT: [[TMP5]] = load %struct.List*, %struct.List** [[NEXT]], align 4
+; CHECK-NEXT: [[TOBOOL:%.*]] = icmp eq %struct.List* [[TMP5]], null
+; CHECK-NEXT: br i1 [[TOBOOL]], label [[IF_ELSE:%.*]], label [[FOR_COND]]
+; CHECK: if.else:
+; CHECK-NEXT: [[NEXT_LCSSA:%.*]] = phi %struct.List** [ [[NEXT]], [[IF_THEN]] ]
+; CHECK-NEXT: store %struct.List* [[DATA]], %struct.List** [[NEXT_LCSSA]], align 4
+; CHECK-NEXT: [[NEXT5:%.*]] = getelementptr inbounds [[STRUCT_LIST]], %struct.List* [[DATA]], i32 0, i32 0
+; CHECK-NEXT: store %struct.List* null, %struct.List** [[NEXT5]], align 4
+; CHECK-NEXT: br label [[FOR_END:%.*]]
+; CHECK: for.cond.if.else6_crit_edge:
+; CHECK-NEXT: [[SPLIT:%.*]] = phi %struct.List* [ [[PREV_0]], [[FOR_COND]] ]
+; CHECK-NEXT: br label [[IF_ELSE6]]
+; CHECK: if.else6:
+; CHECK-NEXT: [[PREV_0_LCSSA:%.*]] = phi %struct.List* [ [[SPLIT]], [[FOR_COND_IF_ELSE6_CRIT_EDGE]] ], [ null, [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[TOBOOL7:%.*]] = icmp eq %struct.List* [[PREV_0_LCSSA]], null
+; CHECK-NEXT: br i1 [[TOBOOL7]], label [[IF_ELSE12:%.*]], label [[IF_THEN8:%.*]]
+; CHECK: if.then8:
+; CHECK-NEXT: [[NEXT9:%.*]] = getelementptr inbounds [[STRUCT_LIST]], %struct.List* [[PREV_0_LCSSA]], i32 0, i32 0
+; CHECK-NEXT: [[TMP6:%.*]] = bitcast %struct.List* [[PREV_0_LCSSA]] to i32*
+; CHECK-NEXT: [[TMP7:%.*]] = load i32, i32* [[TMP6]], align 4
+; CHECK-NEXT: [[TMP8:%.*]] = bitcast %struct.List* [[DATA]] to i32*
+; CHECK-NEXT: store i32 [[TMP7]], i32* [[TMP8]], align 4
+; CHECK-NEXT: store %struct.List* [[DATA]], %struct.List** [[NEXT9]], align 4
+; CHECK-NEXT: br label [[FOR_END]]
+; CHECK: if.else12:
+; CHECK-NEXT: [[TMP9:%.*]] = bitcast %struct.List** [[LIST]] to i32*
+; CHECK-NEXT: [[TMP10:%.*]] = load i32, i32* [[TMP9]], align 4
+; CHECK-NEXT: [[TMP11:%.*]] = bitcast %struct.List* [[DATA]] to i32*
+; CHECK-NEXT: store i32 [[TMP10]], i32* [[TMP11]], align 4
+; CHECK-NEXT: store %struct.List* [[DATA]], %struct.List** [[LIST]], align 4
+; CHECK-NEXT: br label [[FOR_END]]
+; CHECK: for.end:
+; CHECK-NEXT: ret void
+;
+entry:
+ %0 = load %struct.List*, %struct.List** %list, align 4
+ br label %for.cond
+
+for.cond: ; preds = %if.then, %entry
+ %curr.0 = phi %struct.List* [ %0, %entry ], [ %3, %if.then ]
+ %prev.0 = phi %struct.List* [ null, %entry ], [ %curr.0, %if.then ]
+ %val = getelementptr inbounds %struct.List, %struct.List* %curr.0, i32 0, i32 1
+ %1 = load i32, i32* %val, align 4
+ %val1 = getelementptr inbounds %struct.List, %struct.List* %data, i32 0, i32 1
+ %2 = load i32, i32* %val1, align 4
+ %cmp = icmp slt i32 %1, %2
+ br i1 %cmp, label %if.then, label %if.else6
+
+if.then: ; preds = %for.cond
+ %next = getelementptr inbounds %struct.List, %struct.List* %curr.0, i32 0, i32 0
+ %3 = load %struct.List*, %struct.List** %next, align 4
+ %tobool = icmp eq %struct.List* %3, null
+ br i1 %tobool, label %if.else, label %for.cond
+
+if.else: ; preds = %if.then
+ %next.lcssa = phi %struct.List** [ %next, %if.then ]
+ store %struct.List* %data, %struct.List** %next.lcssa, align 4
+ %next5 = getelementptr inbounds %struct.List, %struct.List* %data, i32 0, i32 0
+ store %struct.List* null, %struct.List** %next5, align 4
+ br label %for.end
+
+if.else6: ; preds = %for.cond
+ %prev.0.lcssa = phi %struct.List* [ %prev.0, %for.cond ]
+ %tobool7 = icmp eq %struct.List* %prev.0.lcssa, null
+ br i1 %tobool7, label %if.else12, label %if.then8
+
+if.then8: ; preds = %if.else6
+ %next9 = getelementptr inbounds %struct.List, %struct.List* %prev.0.lcssa, i32 0, i32 0
+ %4 = bitcast %struct.List* %prev.0.lcssa to i32*
+ %5 = load i32, i32* %4, align 4
+ %6 = bitcast %struct.List* %data to i32*
+ store i32 %5, i32* %6, align 4
+ store %struct.List* %data, %struct.List** %next9, align 4
+ br label %for.end
+
+if.else12: ; preds = %if.else6
+ %7 = bitcast %struct.List** %list to i32*
+ %8 = load i32, i32* %7, align 4
+ %9 = bitcast %struct.List* %data to i32*
+ store i32 %8, i32* %9, align 4
+ store %struct.List* %data, %struct.List** %list, align 4
+ br label %for.end
+
+for.end: ; preds = %if.else12, %if.then8, %if.else
+ ret void
+}
+
+define i32 @test2(i32* %l) {
+; CHECK-LABEL: @test2(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = load i32, i32* [[L:%.*]], align 4
+; CHECK-NEXT: [[TOBOOL2:%.*]] = icmp eq i32 [[TMP0]], 0
+; CHECK-NEXT: br i1 [[TOBOOL2]], label [[CLEANUP:%.*]], label [[DO_COND_LR_PH:%.*]]
+; CHECK: do.cond.lr.ph:
+; CHECK-NEXT: br label [[DO_COND:%.*]]
+; CHECK: do.body:
+; CHECK-NEXT: [[A_0:%.*]] = phi i32 [ [[REM:%.*]], [[DO_COND]] ]
+; CHECK-NEXT: [[TMP1:%.*]] = load i32, i32* [[L]], align 4
+; CHECK-NEXT: [[TOBOOL:%.*]] = icmp eq i32 [[TMP1]], 0
+; CHECK-NEXT: br i1 [[TOBOOL]], label [[DO_BODY_CLEANUP_CRIT_EDGE:%.*]], label [[DO_COND]]
+; CHECK: do.body.cleanup_crit_edge:
+; CHECK-NEXT: [[SPLIT:%.*]] = phi i32 [ [[A_0]], [[DO_BODY:%.*]] ]
+; CHECK-NEXT: br label [[CLEANUP]]
+; CHECK: cleanup:
+; CHECK-NEXT: [[A_0_LCSSA:%.*]] = phi i32 [ [[SPLIT]], [[DO_BODY_CLEANUP_CRIT_EDGE]] ], [ 100, [[ENTRY:%.*]] ]
+; CHECK-NEXT: store i32 10, i32* [[L]], align 4
+; CHECK-NEXT: br label [[CLEANUP2:%.*]]
+; CHECK: do.cond:
+; CHECK-NEXT: [[TMP2:%.*]] = phi i32 [ [[TMP0]], [[DO_COND_LR_PH]] ], [ [[TMP1]], [[DO_BODY]] ]
+; CHECK-NEXT: [[MUL:%.*]] = mul nsw i32 [[TMP2]], 13
+; CHECK-NEXT: [[REM]] = srem i32 [[MUL]], 27
+; CHECK-NEXT: [[TMP3:%.*]] = load i32, i32* [[L]], align 4
+; CHECK-NEXT: [[TOBOOL1:%.*]] = icmp eq i32 [[TMP3]], 0
+; CHECK-NEXT: br i1 [[TOBOOL1]], label [[CLEANUP2_LOOPEXIT:%.*]], label [[DO_BODY]]
+; CHECK: cleanup2.loopexit:
+; CHECK-NEXT: br label [[CLEANUP2]]
+; CHECK: cleanup2:
+; CHECK-NEXT: [[RETVAL_2:%.*]] = phi i32 [ [[A_0_LCSSA]], [[CLEANUP]] ], [ 0, [[CLEANUP2_LOOPEXIT]] ]
+; CHECK-NEXT: ret i32 [[RETVAL_2]]
+;
+entry:
+ br label %do.body
+
+do.body: ; preds = %do.cond, %entry
+ %a.0 = phi i32 [ 100, %entry ], [ %rem, %do.cond ]
+ %0 = load i32, i32* %l, align 4
+ %tobool = icmp eq i32 %0, 0
+ br i1 %tobool, label %cleanup, label %do.cond
+
+cleanup: ; preds = %do.body
+ %a.0.lcssa = phi i32 [ %a.0, %do.body ]
+ store i32 10, i32* %l, align 4
+ br label %cleanup2
+
+do.cond: ; preds = %do.body
+ %mul = mul nsw i32 %0, 13
+ %rem = srem i32 %mul, 27
+ %1 = load i32, i32* %l, align 4
+ %tobool1 = icmp eq i32 %1, 0
+ br i1 %tobool1, label %cleanup2.loopexit, label %do.body
+
+cleanup2.loopexit: ; preds = %do.cond
+ br label %cleanup2
+
+cleanup2: ; preds = %cleanup2.loopexit, %cleanup
+ %retval.2 = phi i32 [ %a.0.lcssa, %cleanup ], [ 0, %cleanup2.loopexit ]
+ ret i32 %retval.2
+}
+
+define i32 @no_rotate(i32* %l) {
+; CHECK-LABEL: @no_rotate(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br label [[DO_BODY:%.*]]
+; CHECK: do.body:
+; CHECK-NEXT: [[A_0:%.*]] = phi i32 [ 100, [[ENTRY:%.*]] ], [ [[REM:%.*]], [[DO_COND:%.*]] ]
+; CHECK-NEXT: [[TMP0:%.*]] = load i32, i32* [[L:%.*]], align 4
+; CHECK-NEXT: [[TOBOOL:%.*]] = icmp eq i32 [[TMP0]], 0
+; CHECK-NEXT: br i1 [[TOBOOL]], label [[CLEANUP:%.*]], label [[DO_COND]]
+; CHECK: cleanup:
+; CHECK-NEXT: [[A_0_LCSSA:%.*]] = phi i32 [ [[A_0]], [[DO_BODY]] ]
+; CHECK-NEXT: store i32 10, i32* [[L]], align 4
+; CHECK-NEXT: br label [[CLEANUP2:%.*]]
+; CHECK: do.cond:
+; CHECK-NEXT: [[MUL:%.*]] = mul nsw i32 [[A_0]], 13
+; CHECK-NEXT: [[REM]] = srem i32 [[MUL]], 27
+; CHECK-NEXT: [[TMP1:%.*]] = load i32, i32* [[L]], align 4
+; CHECK-NEXT: [[TOBOOL1:%.*]] = icmp eq i32 [[TMP1]], 0
+; CHECK-NEXT: br i1 [[TOBOOL1]], label [[CLEANUP2_LOOPEXIT:%.*]], label [[DO_BODY]]
+; CHECK: cleanup2.loopexit:
+; CHECK-NEXT: br label [[CLEANUP2]]
+; CHECK: cleanup2:
+; CHECK-NEXT: [[RETVAL_2:%.*]] = phi i32 [ [[A_0_LCSSA]], [[CLEANUP]] ], [ 0, [[CLEANUP2_LOOPEXIT]] ]
+; CHECK-NEXT: ret i32 [[RETVAL_2]]
+;
+entry:
+ br label %do.body
+
+do.body: ; preds = %do.cond, %entry
+ %a.0 = phi i32 [ 100, %entry ], [ %rem, %do.cond ]
+ %0 = load i32, i32* %l, align 4
+ %tobool = icmp eq i32 %0, 0
+ br i1 %tobool, label %cleanup, label %do.cond
+
+cleanup: ; preds = %do.body
+ %a.0.lcssa = phi i32 [ %a.0, %do.body ]
+ store i32 10, i32* %l, align 4
+ br label %cleanup2
+
+do.cond: ; preds = %do.body
+ %mul = mul nsw i32 %a.0, 13
+ %rem = srem i32 %mul, 27
+ %1 = load i32, i32* %l, align 4
+ %tobool1 = icmp eq i32 %1, 0
+ br i1 %tobool1, label %cleanup2.loopexit, label %do.body
+
+cleanup2.loopexit: ; preds = %do.cond
+ br label %cleanup2
+
+cleanup2: ; preds = %cleanup2.loopexit, %cleanup
+ %retval.2 = phi i32 [ %a.0.lcssa, %cleanup ], [ 0, %cleanup2.loopexit ]
+ ret i32 %retval.2
+}
+
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