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https://github.com/c64scene-ar/llvm-6502.git
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ab0d042a74
This is a follow-up to r209358: PR19799: Indvars miscompile due to an incorrect max backedge taken count from SCEV. That fix was incomplete as pointed out by Arnold and Michael Z. The code was also too confusing. It needed a careful rewrite with more unit tests. This version will also happen to optimize more cases. <rdar://17005101> PR19799: Indvars miscompile... git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209545 91177308-0d34-0410-b5e6-96231b3b80d8
183 lines
6.4 KiB
LLVM
183 lines
6.4 KiB
LLVM
; RUN: opt < %s -analyze -scalar-evolution | FileCheck %s
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; ScalarEvolution should be able to understand the loop and eliminate the casts.
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; CHECK: {%d,+,sizeof(i32)}
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define void @foo(i32* nocapture %d, i32 %n) nounwind {
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entry:
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%0 = icmp sgt i32 %n, 0 ; <i1> [#uses=1]
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br i1 %0, label %bb.nph, label %return
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bb.nph: ; preds = %entry
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br label %bb
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bb: ; preds = %bb1, %bb.nph
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%i.02 = phi i32 [ %5, %bb1 ], [ 0, %bb.nph ] ; <i32> [#uses=2]
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%p.01 = phi i8 [ %4, %bb1 ], [ -1, %bb.nph ] ; <i8> [#uses=2]
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%1 = sext i8 %p.01 to i32 ; <i32> [#uses=1]
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%2 = sext i32 %i.02 to i64 ; <i64> [#uses=1]
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%3 = getelementptr i32* %d, i64 %2 ; <i32*> [#uses=1]
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store i32 %1, i32* %3, align 4
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%4 = add i8 %p.01, 1 ; <i8> [#uses=1]
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%5 = add i32 %i.02, 1 ; <i32> [#uses=2]
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br label %bb1
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bb1: ; preds = %bb
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%6 = icmp slt i32 %5, %n ; <i1> [#uses=1]
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br i1 %6, label %bb, label %bb1.return_crit_edge
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bb1.return_crit_edge: ; preds = %bb1
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br label %return
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return: ; preds = %bb1.return_crit_edge, %entry
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ret void
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}
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; ScalarEvolution should be able to find the maximum tripcount
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; of this multiple-exit loop, and if it doesn't know the exact
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; count, it should say so.
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; PR7845
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; CHECK: Loop %for.cond: <multiple exits> Unpredictable backedge-taken count.
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; CHECK: Loop %for.cond: max backedge-taken count is 5
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@.str = private constant [4 x i8] c"%d\0A\00" ; <[4 x i8]*> [#uses=2]
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define i32 @main() nounwind {
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entry:
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br label %for.cond
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for.cond: ; preds = %for.inc, %entry
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%g_4.0 = phi i32 [ 0, %entry ], [ %add, %for.inc ] ; <i32> [#uses=5]
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%cmp = icmp slt i32 %g_4.0, 5 ; <i1> [#uses=1]
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br i1 %cmp, label %for.body, label %for.end
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for.body: ; preds = %for.cond
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%conv = trunc i32 %g_4.0 to i16 ; <i16> [#uses=1]
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%tobool.not = icmp eq i16 %conv, 0 ; <i1> [#uses=1]
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%tobool3 = icmp ne i32 %g_4.0, 0 ; <i1> [#uses=1]
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%or.cond = and i1 %tobool.not, %tobool3 ; <i1> [#uses=1]
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br i1 %or.cond, label %for.end, label %for.inc
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for.inc: ; preds = %for.body
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%add = add nsw i32 %g_4.0, 1 ; <i32> [#uses=1]
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br label %for.cond
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for.end: ; preds = %for.body, %for.cond
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%call = call i32 (i8*, ...)* @printf(i8* getelementptr inbounds ([4 x i8]* @.str, i64 0, i64 0), i32 %g_4.0) nounwind ; <i32> [#uses=0]
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ret i32 0
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}
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declare i32 @printf(i8*, ...)
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define void @test(i8* %a, i32 %n) nounwind {
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entry:
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%cmp1 = icmp sgt i32 %n, 0
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br i1 %cmp1, label %for.body.lr.ph, label %for.end
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for.body.lr.ph: ; preds = %entry
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%tmp = zext i32 %n to i64
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br label %for.body
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for.body: ; preds = %for.body, %for.body.lr.ph
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%indvar = phi i64 [ %indvar.next, %for.body ], [ 0, %for.body.lr.ph ]
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%arrayidx = getelementptr i8* %a, i64 %indvar
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store i8 0, i8* %arrayidx, align 1
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%indvar.next = add i64 %indvar, 1
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%exitcond = icmp ne i64 %indvar.next, %tmp
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br i1 %exitcond, label %for.body, label %for.cond.for.end_crit_edge
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for.cond.for.end_crit_edge: ; preds = %for.body
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br label %for.end
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for.end: ; preds = %for.cond.for.end_crit_edge, %entry
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ret void
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}
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; CHECK: Determining loop execution counts for: @test
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; CHECK-NEXT: backedge-taken count is
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; CHECK-NEXT: max backedge-taken count is -1
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; PR19799: Indvars miscompile due to an incorrect max backedge taken count from SCEV.
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; CHECK-LABEL: @pr19799
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; CHECK: Loop %for.body.i: <multiple exits> Unpredictable backedge-taken count.
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; CHECK: Loop %for.body.i: max backedge-taken count is 1
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@a = common global i32 0, align 4
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define i32 @pr19799() {
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entry:
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store i32 -1, i32* @a, align 4
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br label %for.body.i
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for.body.i: ; preds = %for.cond.i, %entry
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%storemerge1.i = phi i32 [ -1, %entry ], [ %add.i.i, %for.cond.i ]
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%tobool.i = icmp eq i32 %storemerge1.i, 0
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%add.i.i = add nsw i32 %storemerge1.i, 2
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br i1 %tobool.i, label %bar.exit, label %for.cond.i
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for.cond.i: ; preds = %for.body.i
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store i32 %add.i.i, i32* @a, align 4
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%cmp.i = icmp slt i32 %storemerge1.i, 0
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br i1 %cmp.i, label %for.body.i, label %bar.exit
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bar.exit: ; preds = %for.cond.i, %for.body.i
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ret i32 0
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}
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; Here we have a must-exit loop latch that is not computabe and a
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; may-exit early exit that can only have one non-exiting iteration
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; before the check is forever skipped.
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;
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; CHECK-LABEL: @cannot_compute_mustexit
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; CHECK: Loop %for.body.i: <multiple exits> Unpredictable backedge-taken count.
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; CHECK: Loop %for.body.i: Unpredictable max backedge-taken count.
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@b = common global i32 0, align 4
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define i32 @cannot_compute_mustexit() {
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entry:
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store i32 -1, i32* @a, align 4
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br label %for.body.i
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for.body.i: ; preds = %for.cond.i, %entry
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%storemerge1.i = phi i32 [ -1, %entry ], [ %add.i.i, %for.cond.i ]
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%tobool.i = icmp eq i32 %storemerge1.i, 0
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%add.i.i = add nsw i32 %storemerge1.i, 2
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br i1 %tobool.i, label %bar.exit, label %for.cond.i
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for.cond.i: ; preds = %for.body.i
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store i32 %add.i.i, i32* @a, align 4
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%ld = load volatile i32* @b
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%cmp.i = icmp ne i32 %ld, 0
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br i1 %cmp.i, label %for.body.i, label %bar.exit
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bar.exit: ; preds = %for.cond.i, %for.body.i
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ret i32 0
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}
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; This loop has two must-exits, both of with dominate the latch. The
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; MaxBECount should be the minimum of them.
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;
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; CHECK-LABEL: @two_mustexit
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; CHECK: Loop %for.body.i: <multiple exits> Unpredictable backedge-taken count.
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; CHECK: Loop %for.body.i: max backedge-taken count is 1
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define i32 @two_mustexit() {
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entry:
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store i32 -1, i32* @a, align 4
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br label %for.body.i
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for.body.i: ; preds = %for.cond.i, %entry
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%storemerge1.i = phi i32 [ -1, %entry ], [ %add.i.i, %for.cond.i ]
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%tobool.i = icmp sgt i32 %storemerge1.i, 0
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%add.i.i = add nsw i32 %storemerge1.i, 2
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br i1 %tobool.i, label %bar.exit, label %for.cond.i
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for.cond.i: ; preds = %for.body.i
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store i32 %add.i.i, i32* @a, align 4
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%cmp.i = icmp slt i32 %storemerge1.i, 3
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br i1 %cmp.i, label %for.body.i, label %bar.exit
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bar.exit: ; preds = %for.cond.i, %for.body.i
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ret i32 0
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}
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