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Relax the "don't unroll loops containing calls" rule. Instead, when a loop contains a call, lower the

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unrolling threshold to the optimize-for-size threshold.  Basically, for loops containing calls, unrolling
can still be profitable as long as the loop is REALLY small.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113439 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2010-09-08 23:10:07 +00:00
parent a88d8577e6
commit 4975447d94
2 changed files with 55 additions and 2 deletions
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6
lib/Transforms/Scalar/LoopUnrollPass.cpp
View File

@ -132,8 +132,10 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
unsigned LoopSize = ApproximateLoopSize(L, NumCalls);
DEBUG(dbgs() << " Loop Size = " << LoopSize << "\n");
if (NumCalls != 0) {
DEBUG(dbgs() << " Not unrolling loop with function calls.\n");
return false;
// Even for a loop that contains calls, it can still be profitable to
// unroll if the loop is really, REALLY small.
DEBUG(dbgs() <<" Using lower threshold for loop with function calls.\n");
CurrentThreshold = OptSizeUnrollThreshold;
}
uint64_t Size = (uint64_t)LoopSize*Count;
if (TripCount != 1 && Size > CurrentThreshold) {

51
test/Transforms/LoopUnroll/call.ll Normal file
View File

@ -0,0 +1,51 @@
; RUN: opt < %s -S -loop-unroll | FileCheck %s
@id = internal global i32 0
@val = internal global [4 x i32] zeroinitializer, align 16
; CHECK: @test
define i32 @test(i32 %k) nounwind ssp {
; CHECK-NOT: call i32 @test(i32 %t.06)
; CHECK: call i32 @test(i32 0)
; CHECK-NOT: call i32 @test(i32 %t.06)
; CHECK: call i32 @test(i32 1)
; CHECK-NOT: call i32 @test(i32 %t.06)
; CHECK: call i32 @test(i32 2)
; CHECK-NOT: call i32 @test(i32 %t.06)
; CHECK: call i32 @test(i32 3)
; CHECK-NOT: call i32 @test(i32 %t.06)
bb.nph:
%0 = load i32* @id, align 4
%1 = add nsw i32 %0, 1
store i32 %1, i32* @id, align 4
%2 = sext i32 %k to i64
%3 = getelementptr inbounds [4 x i32]* @val, i64 0, i64 %2
store i32 %1, i32* %3, align 4
br label %bb
bb: ; preds = %bb2, %bb.nph
%indvar = phi i64 [ 0, %bb.nph ], [ %indvar.next, %bb2 ]
%scevgep = getelementptr [4 x i32]* @val, i64 0, i64 %indvar
%4 = load i32* %scevgep, align 4
%5 = icmp eq i32 %4, 0
br i1 %5, label %bb1, label %bb2
bb1: ; preds = %bb
%t.06 = trunc i64 %indvar to i32
%6 = tail call i32 @test(i32 %t.06) nounwind
br label %bb2
bb2: ; preds = %bb1, %bb
%indvar.next = add i64 %indvar, 1
%exitcond = icmp eq i64 %indvar.next, 4
br i1 %exitcond, label %bb4, label %bb
bb4: ; preds = %bb2
%.pre = load i32* @id, align 4
%7 = add nsw i32 %.pre, -1
store i32 %7, i32* @id, align 4
store i32 0, i32* %3, align 4
ret i32 undef
; CHECK: }
}